[ { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/h5v2y-18v26", "eprint_id": 119900, "eprint_status": "archive", "datestamp": "2023-08-22 20:18:30", "lastmod": "2023-10-25 16:47:19", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Hutchins-Nicholas", "name": { "family": "Hutchins", "given": "N." }, "orcid": "0000-0003-1599-002X" }, { "id": "Ganapathisubramani-B", "name": { "family": "Ganapathisubramani", "given": "B." } }, { "id": "Schultz-M-P", "name": { "family": "Schultz", "given": "M. P." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Defining an equivalent homogeneous roughness length for turbulent boundary layers developing over patchy or heterogeneous surfaces", "ispublished": "pub", "full_text_status": "public", "keywords": "Ocean Engineering; Environmental Engineering", "note": "\u00a9 2023 Elsevier. \n\nNH gratefully acknowledges support from the Australian Research Council (ARC) and as Millikan Visiting Professor at the California Institute of Technology. DP acknowledges support from the ARC as an international partner investigator. MPS acknowledges support from the US Office of Naval Research. BG gratefully acknowledges support from EPSRC, United Kingdom (Grant ref No: EP/V00199X/1). \n\nData availability. No data was used for the research described in the article. \n\nThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.", "abstract": "A new approach based on the power mean is suggested for defining an equivalent homogeneous roughness length k_(ehr)\n which takes into account patchiness or heterogeneous distribution of roughness on ship hulls and can be readily incorporated into existing full-scale drag prediction methods. In the limit where patch sizes are much greater than the boundary layer thickness, it is readily shown that the relationship between drag coefficient and roughness length is non-linear, highlighting an obvious source of error with current approaches that attempt to define an equivalent homogeneous roughness through an area-weighed arithmetic mean. The degree of error is dependent on the roughness distribution, but is estimated to exceed 16% for highly skewed beta heterogeneous distributions. For fully-rough models, the power-mean approach returns errors of <\n1% for the distributions tested here. The efficacy of the power-mean approach is also evaluated in the transitional regime and with different transitional roughness models (Nikuradse and Colebrook) and retains accuracy for most realistic operating scenarios.", "date": "2023-03-01", "date_type": "published", "publication": "Ocean Engineering", "volume": "271", "publisher": "Elsevier", "pagerange": "Art. No. 113454", "id_number": "CaltechAUTHORS:20230308-467584400.4", "issn": "0029-8018", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230308-467584400.4", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Australian Research Council" }, { "agency": "Office of Naval Research (ONR)" }, { "agency": "Engineering and Physical Sciences Research Council (EPSRC)", "grant_number": "EP/V00199X/1" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1016/j.oceaneng.2022.113454", "resource_type": "article", "pub_year": "2023", "author_list": "Hutchins, N.; Ganapathisubramani, B.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/vkhfe-a7v39", "eprint_id": 119127, "eprint_status": "archive", "datestamp": "2023-08-19 10:42:40", "lastmod": "2024-01-15 21:29:20", "type": "monograph", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pantano-Carlos", "name": { "family": "Pantano", "given": "C." }, "orcid": "0000-0003-3971-2278" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "A statistical description of turbulent diffusion flame holes", "ispublished": "unpub", "full_text_status": "public", "note": "This work was supported by the ASC program of the Department of Energy under Subcontract B341492 of DOE Contract W-7405-ENG-48.\n\n
Accepted Version - cit-asci-tr167.pdf
", "abstract": "A statistical approach to the dynamics of diffusion-flame holes is presented. The dynamics of the holes are assumed to be controlled by the edge-flame velocity that is determined by the mixture fraction rate of dissipation, a random variable in a turbulent flow. The formulation is then specialized to the case of small circular holes and a stochastic model is used to investigate the dynamics of the joint probability density function of flame-hole radius and scalar dissipation. The associated Fokker\u2013Planck transport equation for the joint pdf is solved and the hole area evolution with time is computed. Furthermore, the one-dimensional marginal probability density function transport equation for the hole radius is derived and the conditional edge-flame velocity is studied for both expanding and collapsing holes.", "date": "2023-02-11", "date_type": "published", "publisher": "Caltech Library", "id_number": "CaltechAUTHORS:20230209-234936651", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230209-234936651", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Department of Energy (DOE)", "grant_number": "B341492" }, { "agency": "Department of Energy (DOE)", "grant_number": "W-7405-ENG-48" } ] }, "local_group": { "items": [ { "id": "Accelerated-Strategic-Computing-Initiative" }, { "id": "GALCIT" } ] }, "primary_object": { "basename": "cit-asci-tr167.pdf", "url": "https://authors.library.caltech.edu/records/vkhfe-a7v39/files/cit-asci-tr167.pdf" }, "resource_type": "monograph", "pub_year": "2023", "author_list": "Pantano, C. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/0saj7-g8r28", "eprint_id": 119124, "eprint_status": "archive", "datestamp": "2023-08-19 10:42:30", "lastmod": "2024-01-15 21:29:16", "type": "monograph", "metadata_visibility": "show", "creators": { "items": [ { "id": "Hill-D-J", "name": { "family": "Hill", "given": "D. J." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Hybrid Tuned Center Difference - WENO Method for Large Eddy Simulations in the Presence of Strong Shocks", "ispublished": "unpub", "full_text_status": "public", "note": "This work was supported by the Academic Strategic Alliances Program of the Accelerated Strategic Computing Initiative (ASCI/ASAP) under subcontract no. B341492 of DOE contract W-7405-ENG-48.\n\nAccepted Version - cit-asci-tr170.pdf
", "abstract": "We develop a tuned center-difference (TCD) scheme optimized for large-eddy simulations (LES) using a method proposed by Ghosal. For LES of weakly compressible decaying turbulence, these optimized stencils are shown to provide superior performance when compared to higher-order centered schemes with the same stencil width. A hybrid method combining the TCD stencil with a weighted essentially non-oscillatory (WENO) method is then constructed for use in the LES of strongly compressible, shock-driven flows. The user-specified, optimum WENO weights are chosen to match those of the TCD scheme. It is expected that these weights will be achieved automatically in regions of smooth flow away from shocks, but in practice a switch is found to be necessary. The hybrid TCD\u2013WENO scheme is shown to work well for unsteady gas-dynamic flows in one and two dimensions.", "date": "2023-02-10", "date_type": "published", "publisher": "Caltech Library", "id_number": "CaltechAUTHORS:20230209-233611005", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230209-233611005", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Department of Energy (DOE)", "grant_number": "B341492" }, { "agency": "Department of Energy (DOE)", "grant_number": "W-7405-ENG-48" } ] }, "local_group": { "items": [ { "id": "Accelerated-Strategic-Computing-Initiative" }, { "id": "GALCIT" } ] }, "primary_object": { "basename": "cit-asci-tr170.pdf", "url": "https://authors.library.caltech.edu/records/0saj7-g8r28/files/cit-asci-tr170.pdf" }, "resource_type": "monograph", "pub_year": "2023", "author_list": "Hill, D. J. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/nne5m-p8b77", "eprint_id": 119057, "eprint_status": "archive", "datestamp": "2023-08-22 18:48:30", "lastmod": "2023-10-24 23:48:59", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Cheng-Wan", "name": { "family": "Cheng", "given": "W." }, "orcid": "0000-0003-3960-4162" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Samtaney-Ravi", "name": { "family": "Samtaney", "given": "R." }, "orcid": "0000-0002-4702-6473" }, { "id": "Luo-Xisheng", "name": { "family": "Luo", "given": "X." }, "orcid": "0000-0002-4303-8290" } ] }, "title": "Numerical simulation of turbulent, plane parallel Couette-Poiseuille flow", "ispublished": "pub", "full_text_status": "public", "keywords": "Mechanical Engineering; Mechanics of Materials; Condensed Matter Physics; Applied Mathematics", "note": "This work was supported by the National Natural Science Foundation of China (nos 12172352, 91952205 and 11621202). The Cray XC40, Shaheen, at KAUST was utilized for the reported DNS and WRLES.", "abstract": "We present numerical simulation and mean-flow modelling of statistically stationary plane Couette\u2013Poiseuille flow in a parameter space (Re,\u03b8) with Re = \u221a[Re\ua700\u00b2 + Re\u00b2_M] and \u03b8 = arctan (Re_M/Re\ua700, where Re\ua700, Re_M are independent Reynolds numbers based on the plate speed U\ua700 and the volume flow rate per unit span, respectively. The database comprises direct numerical simulations (DNS) at Re = 4000, 6000, wall-resolved large-eddy simulations at Re = 10000, 20000, and some wall-modelled large-eddy simulations (WMLES) up to Re = 10\u00b9\u2070. Attention is focused on the transition (from Couette-type to Poiseuille-type flow), defined as where the mean skin-friction Reynolds number on the bottom wall Re_(\u03c4,b), changes sign at \u03b8 = \u03b8\ua700(Re). The mean flow in the (Re,\u03b8) plane is modelled with combinations of patched classical log-wake profiles. Several model versions with different structures are constructed in both the Couette-type and Poiseuille-type flow regions. Model calculations of Re_(\u03c4,b)(Re,\u03b8), Re_(\u03c4,t)(Re,\u03b8) (the skin-friction Reynolds number on the top wall) and \u03b8\ua700 show general agreement with both DNS and large-eddy simulations. Both model and simulation indicate that, as \u03b8 is increased at fixed Re, Re_(\u03c4,t) passes through a peak at approximately \u03b8 = 45\u00b0, while Re_(\u03c4,b) increases monotonically. Near the bottom wall, the flow laminarizes as \u03b8 passes through \u03b8_(c) and then re-transitions to turbulence. As Re increases, \u03b8\ua700 increases monotonically. The transition from Couette-type to Poiseuille-type flow is accompanied by the rapid attenuation of streamwise rolls observed in pure Couette flow. A subclass of flows with Re_(\u03c4,b) = 0 is investigated. Combined WMLES with modelling for these flows enables exploration of the Re \u2192 \u221e limit, giving \u03b8\ua700 \u2192 45\u00b0 as Re \u2192 \u221e.", "date": "2023-01-25", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "955", "publisher": "Cambridge University Press", "pagerange": "Art. No. A4", "id_number": "CaltechAUTHORS:20230206-9037800.10", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230206-9037800.10", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "National Natural Science Foundation of China", "grant_number": "11621202" }, { "agency": "National Natural Science Foundation of China", "grant_number": "12172352" }, { "agency": "National Natural Science Foundation of China", "grant_number": "91952205" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/jfm.2022.1023", "resource_type": "article", "pub_year": "2023", "author_list": "Cheng, W.; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/ge3kn-b9m60", "eprint_id": 117271, "eprint_status": "archive", "datestamp": "2023-08-22 17:59:08", "lastmod": "2023-10-24 22:27:59", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Li-Mogeng", "name": { "family": "Li", "given": "Mogeng" }, "orcid": "0000-0002-9875-6468" }, { "id": "de-Silva-Charitha-M", "name": { "family": "de Silva", "given": "Charitha M." }, "orcid": "0000-0001-9517-4318" }, { "id": "Chung-Daniel", "name": { "family": "Chung", "given": "Daniel" }, "orcid": "0000-0003-3732-364X" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "Dale I." } }, { "id": "Marusic-Ivan", "name": { "family": "Marusic", "given": "Ivan" }, "orcid": "0000-0003-2700-8435" }, { "id": "Hutchins-Nicholas", "name": { "family": "Hutchins", "given": "Nicholas" }, "orcid": "0000-0003-1599-002X" } ] }, "title": "Modelling the downstream development of a turbulent boundary layer following a step change of roughness", "ispublished": "pub", "full_text_status": "public", "keywords": "JFM classification: Turbulent Flows: Turbulent boundary layers; Mechanical Engineering; Mechanics of Materials; Condensed Matter Physics; Applied Mathematics", "note": "Published online by Cambridge University Press: 23 September 2022.\n\nThis research was supported under the Australian Research Council's Discovery and Linkage Projects funding scheme (projects DP160103619 and LP190101134).", "abstract": "In this study, we develop an analytical model to predict the turbulent boundary layer downstream of a step-change in the surface roughness where upstream flow conditions are given. We first revisit the classical model of Elliott (Trans. Am. Geophys. Union, vol. 39, 1958, pp. 1048\u20131054), who modelled the velocity distribution within and above the internal layer with a simple piecewise logarithmic profile, and evolved the velocity profile using the streamwise momentum equation. Elliott's model was originally developed for an atmospheric surface layer, and to make the model applicable to a spatially developing turbulent boundary layer with finite thickness, we propose a number of more physical refinements, including adding a wake function to the velocity profile, considering the growth of the entire boundary layer in the streamwise direction, and using a more realistic shear stress profile in the momentum equation. In particular, we implement the blending model (Li et al., J. Fluid Mech., vol. 923, 2021, p. A18) to account for the deviation of the mean flow within the internal layer from a canonical velocity profile based on the local wall condition. These refinements lead to improved agreement between the prediction and the measurement, especially in the vicinity of the rough-to-smooth change.", "date": "2022-10-25", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "949", "publisher": "Cambridge University Press", "pagerange": "Art. No. A7", "id_number": "CaltechAUTHORS:20221005-265369100.9", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221005-265369100.9", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Australian Research Council", "grant_number": "DP160103619" }, { "agency": "Australian Research Council", "grant_number": "LP190101134" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/jfm.2022.731", "resource_type": "article", "pub_year": "2022", "author_list": "Li, Mogeng; de Silva, Charitha M.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/a9azy-g2h55", "eprint_id": 115775, "eprint_status": "archive", "datestamp": "2023-08-22 16:49:07", "lastmod": "2023-10-24 16:43:29", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Baker-Gregory", "name": { "family": "Baker", "given": "Gregory" } }, { "id": "Chang-Ching", "name": { "family": "Chang", "given": "Ching" }, "orcid": "0000-0003-0923-2644" }, { "id": "Llewellyn-Smith-Stefan-G", "name": { "family": "Llewellyn Smith", "given": "Stefan G." }, "orcid": "0000-0002-1419-6505" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Long-wavelength equations of motion for thin double vorticity layers", "ispublished": "pub", "full_text_status": "restricted", "keywords": "vortex dynamics, contour dynamics, general fluid mechanics; Mechanical Engineering; Mechanics of Materials; Condensed Matter Physics", "note": "\u00a9 The Author(s), 2022. Published by Cambridge University Press. \n\n(Received 5 October 2021; revised 9 April 2022; accepted 11 April 2022) \n\nThis work has been partially supported under NSF award CBET-1706934. \n\nThe authors report no conflict of interest.", "abstract": "We consider the time evolution in two spatial dimensions of a double vorticity layer consisting of two contiguous, infinite material fluid strips, each with uniform but generally differing vorticity, embedded in an otherwise infinite, irrotational, inviscid incompressible fluid. The potential application is to the wake dynamics formed by two boundary layers separating from a splitter plate. A thin-layer approximation is constructed where each layer thickness, measured normal to the common centre curve, is small in comparison with the local radius of curvature of the centre curve. The three-curve equations of contour dynamics that fully describe the double-layer dynamics are expanded in the small thickness parameter. At leading order, closed nonlinear initial-value evolution equations are obtained that describe the motion of the centre curve together with the time and spatial variation of each layer thickness. In the special case where the layer vorticities are equal, these equations reduce to the single-layer equation of Moore (Stud. Appl. Math., vol. 58, 1978, pp. 119\u2013140). Analysis of the linear stability of the first-order equations to small-amplitude perturbations shows Kelvin\u2013Helmholtz instability when the far-field fluid velocities on either side of the double layer are unequal. Equal velocities define a circulation-free double vorticity layer, for which solution of the initial-value problem using the Laplace transform reveals a double pole in transform space leading to linear algebraic growth in general, but there is a class of interesting initial conditions with no linear growth. This is shown to agree with the long-wavelength limit of the full linearized, three-curve stability equations.", "date": "2022-07-10", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "942", "publisher": "Cambridge University Press", "pagerange": "Art. No. A5", "id_number": "CaltechAUTHORS:20220722-768908000", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220722-768908000", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF", "grant_number": "CBET-1706934" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/jfm.2022.342", "resource_type": "article", "pub_year": "2022", "author_list": "Baker, Gregory; Chang, Ching; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/cyzmg-25126", "eprint_id": 113841, "eprint_status": "archive", "datestamp": "2023-08-22 14:33:13", "lastmod": "2023-10-23 23:15:12", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Cheng-Wan", "name": { "family": "Cheng", "given": "W." }, "orcid": "0000-0003-3960-4162" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Samtaney-Ravi", "name": { "family": "Samtaney", "given": "R." }, "orcid": "0000-0002-4702-6473" } ] }, "title": "Wall-resolved and wall-modelled large-eddy simulation of plane Couette flow", "ispublished": "pub", "full_text_status": "restricted", "keywords": "turbulence simulation; Mechanical Engineering; Mechanics of Materials; Condensed Matter Physics", "note": "\u00a9 The Author(s), 2022. Published by Cambridge University Press. \n\n(Received 11 April 2021; revised 18 August 2021; accepted 21 November 2021) \n\nThis work was partially supported by the KAUST baseline research funds of R.S. The Cray XC40, Shaheen, at KAUST was used for all the reported LES. \n\nThe authors report no conflict of interest.", "abstract": "We describe wall-resolved and wall-modelled large-eddy simulation (LES) of plane Couette (PC) flow. Subgrid-scale (SGS) motion is represented using the Re_\u03c4 = 220$, wall-resolved LES at Re_\u03c4 ~ 500-3600 and wall-modelled LES at Re_\u03c4 ~ 3600-- 2.8 x 10\u2075. All LES performed show the presence of approximately spanwise periodic sets of streamwise rolls. Averaged (including spanwise) wall-normal profiles of the mean streamwise velocity show a consistent log region across all Reynolds numbers. Two distinct measures of turbulent intensity are explored, one of which recognizes the roll structure and one that does not. The spanwise variation of turbulence flow metrics is investigated. Mean streamwise velocity profiles show substantial spanwise variation but collapse well when normalized by local skin-friction velocities. Similar collapse is found for streamwise turbulent intensities. For all present LES, the mean skin-friction variation with the plate Reynolds number is found to match a simple analytical form (Pirozzoli et al., J. Fluid Mech., vol. 758, 2014, pp. 327\u2013343) while the scaled centre-plane, mean-velocity gradient exhibits an inverse ProductLog dependence. Both the mean-flow roll energy and circulation, scaled with outer variables, decrease monotonically for Re_\u03c4 \u2273 500. At lower Re_\u03c4, the mean streamwise zero-velocity line follows a wavy form in the spanwise direction, while at our larger Re_\u03c4, a mushroom shape emerges which could potentially enhance local momentum transport in the spanwise direction and be responsible for the weakening of the spanwise rolls.", "date": "2022-03-10", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "934", "publisher": "Cambridge University Press", "pagerange": "Art. No. A19", "id_number": "CaltechAUTHORS:20220309-965615000", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220309-965615000", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "King Abdullah University of Science and Technology (KAUST)" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/jfm.2021.1046", "resource_type": "article", "pub_year": "2022", "author_list": "Cheng, W.; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/ah4x9-pfe89", "eprint_id": 110341, "eprint_status": "archive", "datestamp": "2023-08-20 05:12:04", "lastmod": "2023-10-23 19:36:00", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Li-Mogeng", "name": { "family": "Li", "given": "Mogeng" }, "orcid": "0000-0002-9875-6468" }, { "id": "de-Silva-Charitha-M", "name": { "family": "de Silva", "given": "Charitha M." }, "orcid": "0000-0001-9517-4318" }, { "id": "Chung-Daniel", "name": { "family": "Chung", "given": "Daniel" }, "orcid": "0000-0003-3732-364X" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "Dale I." } }, { "id": "Marusic-Ivan", "name": { "family": "Marusic", "given": "Ivan" }, "orcid": "0000-0003-2700-8435" }, { "id": "Hutchins-Nicholas", "name": { "family": "Hutchins", "given": "Nicholas" }, "orcid": "0000-0003-1599-002X" } ] }, "title": "Experimental study of a turbulent boundary layer with a rough-to-smooth change in surface conditions at high Reynolds numbers", "ispublished": "pub", "full_text_status": "restricted", "note": "\u00a9 The Author(s), 2021. Published by Cambridge University Press. \n\nReceived 8 December 2020; revised 20 April 2021; accepted 21 June 2021. \n\nThis research was partially supported under the Australian Research Council's Discovery Projects funding scheme (project DP160103619). \n\nThe authors report no conflict of interest.", "abstract": "This study presents an experimental dataset documenting the evolution of a turbulent boundary layer downstream of a rough-to-smooth surface transition. To investigate the effect of upstream flow conditions, two groups of experiments are conducted. For the Group-Re cases, a nominally constant viscous-scaled equivalent sand grain roughness k\u207a_(s0)\u2248160 is maintained on the rough surface, while the friction Reynolds number Re_(\u03c40) ranges from 7100 to 21 000. For the Group-ks cases, Re_(\u03c40)\u224814000 is maintained while k\u207a_(s0) ranges from 111 to 228. The wall-shear stress on the downstream smooth surface is measured directly using oil-film interferometry to redress previously reported uncertainties in the skin-friction coefficient recovery trends. In the early development following the roughness transition, the flow in the internal layer is not in equilibrium with the wall-shear stress. This conflicts with the common practise of modelling the mean velocity profile as two log laws below and above the internal layer height, as first proposed by Elliott (Trans. Am. Geophys. Union, vol. 39, 1958, pp. 1048\u20131054). As a solution to this, the current data are used to model the recovering mean velocity semi-empirically by blending the corresponding rough-wall and smooth-wall profiles. The over-energised large-scale motions leave a strong footprint in the near-wall region of the energy spectrum, the frequency and magnitude of which exhibit dependence on Re_(\u03c40) and k\u207a_(s0), respectively. The energy distribution in near-wall small scales is mostly unaffected by the presence of the outer flow with rough-wall characteristics, which can be used as a surrogate measure to extract the local friction velocity.", "date": "2021-09-25", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "923", "publisher": "Cambridge University Press", "pagerange": "Art. No. A18", "id_number": "CaltechAUTHORS:20210821-001444301", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210821-001444301", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Australian Research Council", "grant_number": "DP160103619" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/jfm.2021.577", "resource_type": "article", "pub_year": "2021", "author_list": "Li, Mogeng; de Silva, Charitha M.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/8jfq2-gvg19", "eprint_id": 105988, "eprint_status": "archive", "datestamp": "2023-08-20 01:30:04", "lastmod": "2023-10-20 22:57:14", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Yu-Ke", "name": { "family": "Yu", "given": "Ke" }, "orcid": "0000-0003-0157-4471" }, { "id": "Colonius-T", "name": { "family": "Colonius", "given": "Tim" }, "orcid": "0000-0003-0326-3909" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Winckelmans-Gr\u00e9goire", "name": { "family": "Winckelmans", "given": "Gr\u00e9goire" } } ] }, "title": "Dynamics and decay of a spherical region of turbulence in free space", "ispublished": "pub", "full_text_status": "public", "keywords": "turbulence simulation, turbulence theory", "note": "\u00a9 2020 The Author(s). Published by Cambridge University Press. \n\nReceived 1 June 2020; revised 20 August 2020; accepted 22 September 2020. Published online by Cambridge University Press: 27 November 2020. \n\nThis work was supported by the ONR grant no. N00014-16-1-2734 and the AFOSR/UCLA grant no. FA9550-18-1-0440. \n\nThe authors report no conflict of interest.\n\nSubmitted - 2009.10364.pdf
", "abstract": "We perform direct numerical simulation and large-eddy simulation of an initially spherical region of turbulence evolving in free space. The computations are performed with a lattice Green's function method, which allows the exact free-space boundary conditions to be imposed on a compact vortical region. Large-eddy simulations are conducted with the stretched vortex subgrid stress model. The initial condition is spherically windowed, isotropic homogeneous incompressible turbulence. We study the spectrum and statistics of the decaying turbulence and compare the results with decaying isotropic turbulence, including cases representing different low-wavenumber behaviour of the energy spectrum (i.e. k\u00b2 versus k\u2074). At late times the turbulent sphere expands with both mean radius and integral scale showing similar timewise growth exponents. The low-wavenumber behaviour has little effect on the inertial scales, and we find that decay rates follow the predictions of Saffman (J. Fluid Mech., vol. 27, 1967, pp. 581\u2013593) in both cases, at least until approximately 400 initial eddy turnover times. The boundary of the spherical region develops intermittency and features ejections of vortex rings. These are shown to occur at the integral scale of the initial turbulence field and are hypothesized to occur due to a local imbalance of impulse on this scale.", "date": "2021-01-25", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "907", "publisher": "Cambridge University Press", "pagerange": "Art. No. A19", "id_number": "CaltechAUTHORS:20201012-140154360", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20201012-140154360", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Office of Naval Research (ONR)", "grant_number": "N00014-16-1-2734" }, { "agency": "Air Force Office of Scientific Research (AFOSR)", "grant_number": "FA9550-18-1-0440" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/jfm.2020.818", "primary_object": { "basename": "2009.10364.pdf", "url": "https://authors.library.caltech.edu/records/8jfq2-gvg19/files/2009.10364.pdf" }, "resource_type": "article", "pub_year": "2021", "author_list": "Yu, Ke; Colonius, Tim; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/kxbvz-9z979", "eprint_id": 107115, "eprint_status": "archive", "datestamp": "2023-08-20 01:30:12", "lastmod": "2023-10-23 15:32:46", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Shen-Naijian", "name": { "family": "Shen", "given": "N." }, "orcid": "0000-0002-0533-8081" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Samtaney-Ravi", "name": { "family": "Samtaney", "given": "R." }, "orcid": "0000-0002-4702-6473" }, { "id": "Wheatley-Vincent", "name": { "family": "Wheatley", "given": "V." }, "orcid": "0000-0002-7287-7659" } ] }, "title": "Evolution of a shock generated by an impulsively accelerated, sinusoidal piston", "ispublished": "pub", "full_text_status": "restricted", "keywords": "gas dynamics, shock waves, nonlinear instability", "note": "\u00a9 The Author(s) 2020. Published by Cambridge University Press. \n\nReceived 30 April 2020; revised 1 August 2020; accepted 9 September 2020. Published online by Cambridge University Press: 26 November 2020. \n\nThis work was supported by the KAUST Office of Sponsored Research under Award No. URF/1/3418-01. The authors also thank Professor H. G. Hornung for helpful discussions. \n\nThe authors report no conflict of interest.", "abstract": "We consider the evolution of a shock wave generated by an impulsively accelerated, two-dimensional, almost planar piston with a sinusoidally corrugated surface of amplitude \u03f5. We develop a complex-variable formulation for a nonlinear theory of generalized geometrical shock dynamics (GGSD) (Best, Shock Waves, vol. 1, issue 4, 1991, pp. 251\u2013273; Best, Proc. R. Soc. Lond. A, vol. 442, 1993, pp. 585\u2013598) as a hierarchical expansion of the Euler equations that can be closed at any order. The zeroth-order truncation of GGSD is related to the equations of Whitham's geometrical shock dynamics (GSD), while higher-order corrections incorporate non-uniformity of the flow immediately behind the piston-driven shock. Numerical solutions to GGSD systems up to second order are coupled to an edge-detection algorithm in order to investigate the hypothesized development of a shock-shape curvature singularity as the rippled shock evolves. This singular behaviour, together with the simultaneous development of a Mach-number discontinuity, is found at all orders of the GGSD hierarchy for both weak and strong shocks. The critical time at which a curvature singularity occurs converges as the order of the GGSD system increases at fixed \u03f5, and follows a scaling inversely proportional to \u03f5 at sufficiently small values. This result agrees with the weakly nonlinear GSD analysis of Mostert et al. (J. Fluid Mech., vol. 846, 2018, pp. 536\u2013562) for a general Mach-number perturbation on a planar shock, and suggests that this represents the universal behaviour of a slightly perturbed, planar shock.", "date": "2021-01-25", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "907", "publisher": "Cambridge University Press", "pagerange": "Art. No. A35", "id_number": "CaltechAUTHORS:20201216-084823910", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20201216-084823910", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "King Abdullah University of Science and Technology (KAUST)", "grant_number": "URF/1/3418-01" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/jfm.2020.775", "resource_type": "article", "pub_year": "2021", "author_list": "Shen, N.; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/def7e-1r693", "eprint_status": "archive", "datestamp": "2023-10-09 23:24:09", "lastmod": "2023-10-09 23:24:09", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Sader-J-E", "name": { "family": "Sader", "given": "John E." }, "orcid": "0000-0002-7096-0627" } ] }, "title": "On the starting vortex generated by a translating and rotating flat plate", "ispublished": "pub", "full_text_status": "public", "keywords": "Mechanical Engineering; Mechanics of Materials; Condensed Matter Physics", "note": "\u00a9 The Author(s), 2020. Published by Cambridge University Press.
\n\nThe authors thank T. Colonius and T. Leonard for stimulating discussion. J.E.S. acknowledges support from the Australian Research Council Centre of Excellence in Exciton Science (CE170100026) and the Australian Research Council grants scheme.
", "abstract": "We consider the trailing-edge vortex produced in an inviscid fluid by the start-up motion of a two-dimensional flat plate. A general starting motion is studied that includes the initial angle-of-attack of the plate (which may be zero), individual time power laws for plate translational and rotational speeds and the pivot position for plate rotation. A vortex-sheet representation for a start-up separated flow at the trailing edge is developed whose time-wise evolution is described by a Birkhoff\u2013Rott equation coupled to an appropriate Kutta condition. This description includes convection by the outer flow, rotation and vortex-image self-induction. It admits a power-law similarity solution for the (small-time) primitive vortex, leading to an equation set where each term carries its own time-wise power-law factor. A set of four general plate motions is defined. Dominant-balance analysis of this set leads to discovery of three distinct start-up vortex-structure types that form the basis for all vortex motion. The properties of each type are developed in detail for some special cases. Numerical and analytical solutions are described and transition between solution types is discussed. Singular and degenerate vortex behaviour is discovered which may be due to the absence of fluid viscosity. An interesting case is start-up motion with zero initial angle of attack coupled to power-law plate rotation for which time-series examples are given that can be compared to high Reynolds number viscous flows.
", "date": "2021-01-10", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "906", "publisher": "Cambridge University Press", "pagerange": "A9", "issn": "0022-1120", "official_url": "https://authors.library.caltech.edu/records/def7e-1r693", "funders": { "items": [ { "grant_number": "CE170100026" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/jfm.2020.762", "resource_type": "article", "pub_year": "2021", "author_list": "Pullin, D. I. and Sader, John E." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/9qkkv-2ax14", "eprint_id": 106839, "eprint_status": "archive", "datestamp": "2023-08-20 01:22:05", "lastmod": "2023-10-20 23:51:12", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Sader-John-E", "name": { "family": "Sader", "given": "John E." }, "orcid": "0000-0002-7096-0627" } ] }, "title": "On the starting vortex generated by a translating and rotating flat plate", "ispublished": "pub", "full_text_status": "restricted", "keywords": "vortex dynamics, vortex shedding", "note": "\u00a9 2020 The Author(s). Published by Cambridge University Press. \n\nReceived 21 April 2020; revised 22 July 2020; accepted 8 September 2020. \n\nThe authors thank T. Colonius and T. Leonard for stimulating discussion. J.E.S. acknowledges support from the Australian Research Council Centre of Excellence in Exciton Science (CE170100026) and the Australian Research Council grants scheme.", "abstract": "We consider the trailing-edge vortex produced in an inviscid fluid by the start-up motion of a two-dimensional flat plate. A general starting motion is studied that includes the initial angle-of-attack of the plate (which may be zero), individual time power laws for plate translational and rotational speeds and the pivot position for plate rotation. A vortex-sheet representation for a start-up separated flow at the trailing edge is developed whose time-wise evolution is described by a Birkhoff\u2013Rott equation coupled to an appropriate Kutta condition. This description includes convection by the outer flow, rotation and vortex-image self-induction. It admits a power-law similarity solution for the (small-time) primitive vortex, leading to an equation set where each term carries its own time-wise power-law factor. A set of four general plate motions is defined. Dominant-balance analysis of this set leads to discovery of three distinct start-up vortex-structure types that form the basis for all vortex motion. The properties of each type are developed in detail for some special cases. Numerical and analytical solutions are described and transition between solution types is discussed. Singular and degenerate vortex behaviour is discovered which may be due to the absence of fluid viscosity. An interesting case is start-up motion with zero initial angle of attack coupled to power-law plate rotation for which time-series examples are given that can be compared to high Reynolds number viscous flows.", "date": "2021-01-10", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "906", "publisher": "Cambridge University Press", "pagerange": "Art. No. A9", "id_number": "CaltechAUTHORS:20201130-084522897", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20201130-084522897", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Australian Research Council", "grant_number": "CE170100026" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/jfm.2020.762", "resource_type": "article", "pub_year": "2021", "author_list": "Pullin, D. I. and Sader, John E." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/pmnfs-5nh83", "eprint_id": 106121, "eprint_status": "archive", "datestamp": "2023-08-20 00:27:55", "lastmod": "2023-10-20 23:06:42", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Bond-D", "name": { "family": "Bond", "given": "D." }, "orcid": "0000-0001-5261-3720" }, { "id": "Wheatley-V", "name": { "family": "Wheatley", "given": "V." } }, { "id": "Li-Y", "name": { "family": "Li", "given": "Y." } }, { "id": "Samtaney-R", "name": { "family": "Samtaney", "given": "R." }, "orcid": "0000-0002-4702-6473" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "The magnetised Richtmyer\u2013Meshkov instability in two-fluid plasmas", "ispublished": "pub", "full_text_status": "public", "keywords": "nonlinear instability, plasmas", "note": "\u00a9 The Author(s), 2020. Published by Cambridge University Press. \n\nReceived 2 February 2020; revised 14 June 2020; accepted 31 July 2020. Published online by Cambridge University Press: 30 September 2020. \n\nThis research was supported by the KAUST Office of Sponsored Research under Award URF/1/3418-01. \n\nThe authors report no conflict of interest.\n\nSubmitted - 2003.00275.pdf
", "abstract": "We investigate the effects of magnetisation on the two-fluid plasma Richtmyer\u2013Meshkov instability of a single-mode thermal interface using a computational approach. The initial magnetic field is normal to the mean interface location. Results are presented for a magnetic interaction parameter of 0.1 and plasma skin depths ranging from 0.1 to 10 perturbation wavelengths. These are compared to initially unmagnetised and neutral fluid cases. The electron flow is found to be constrained to lie along the magnetic field lines resulting in significant longitudinal flow features that interact strongly with the ion fluid. The presence of an initial magnetic field is shown to suppress the growth of the initial interface perturbation with effectiveness determined by plasma length scale. Suppression of the instability is attributed to the magnetic field's contribution to the Lorentz force. This acts to rotate the vorticity vector in each fluid about the local magnetic-field vector leading to cyclic inversion and transport of the out-of-plane vorticity that drives perturbation growth. The transport of vorticity along field lines increases with decreasing plasma length scales and the wave packets responsible for vorticity transport begin to coalesce. In general, the two-fluid plasma Richtmyer\u2013Meshkov instability is found to be suppressed through the action of the imposed magnetic field with increasing effectiveness as plasma length scale is decreased. For the conditions investigated, a critical skin depth for instability suppression is estimated.", "date": "2020-11-25", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "903", "publisher": "Cambridge University Press", "pagerange": "Art. No. A41", "id_number": "CaltechAUTHORS:20201016-145223202", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20201016-145223202", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "King Abdullah University of Science and Technology (KAUST)", "grant_number": "URF/1/3418-01" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/jfm.2020.661", "primary_object": { "basename": "2003.00275.pdf", "url": "https://authors.library.caltech.edu/records/pmnfs-5nh83/files/2003.00275.pdf" }, "resource_type": "article", "pub_year": "2020", "author_list": "Bond, D.; Wheatley, V.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/dy8pc-mtz79", "eprint_id": 103767, "eprint_status": "archive", "datestamp": "2023-08-19 21:38:04", "lastmod": "2023-10-20 16:41:46", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Shen-Naijian", "name": { "family": "Shen", "given": "Naijian" }, "orcid": "0000-0002-0533-8081" }, { "id": "Wheatley-Vincent", "name": { "family": "Wheatley", "given": "Vincent" } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Samtaney-Ravi", "name": { "family": "Samtaney", "given": "Ravi" }, "orcid": "0000-0002-4702-6473" } ] }, "title": "Magnetohydrodynamic Richtmyer\u2013Meshkov instability under an arbitrarily oriented magnetic field", "ispublished": "pub", "full_text_status": "public", "note": "\u00a9 2020 The Author(s). Published under license by AIP Publishing. \n\nSubmitted: 10 December 2019. Accepted: 08 May 2020. Published Online: 05 June 2020. \n\nThis work was supported by the KAUST Office of Sponsored Research under Award No. URF/1/3418\u201301. Dr. Wheatley was supported by the Australian Research Council Discovery Early Career Researcher Award (Project No. DE120102942) and the Australian Research Council's Discovery Projects funding scheme (Project No. DP120102378). \n\nDATA AVAILABILITY: The data that support the findings of this study are available from the corresponding author upon reasonable request.\n\nPublished - 1.5142042.pdf
", "abstract": "The effect of an initially uniform magnetic field of arbitrary orientation on the Richtmyer\u2013Meshkov instability in Hall-magnetohydrodynamics (MHD) and ideal MHD is considered. Attention is restricted to the case where the initial density interface has a single-mode sinusoidal perturbation in amplitude and is accelerated by a shock traveling perpendicular to the interface. An incompressible Hall-MHD model for this flow is developed by solving the relevant impulse-driven linearized initial value problem. The ideal MHD theory is naturally obtained by taking the limit of vanishing ion skin depth. It is shown that the out-of-plane magnetic field component normal to both the impulse and the interface perturbation does not affect the evolution of the flow. For all field orientations other than strictly out-of-plane, the growth of interface perturbations is suppressed. However, the suppression is most effective for near tangential fields but becomes less effective with increasing ion skin depth and Larmor radius. The modeled suppression mechanism is transport of vorticity along magnetic field lines via Alfv\u00e9n fronts in ideal MHD, and via a dispersive wave system in Hall-MHD. Oscillation of the interface growth rate is caused by a continuous phase change of the induced velocities at the interface due to vorticity transport parallel to the perturbation direction in ideal MHD, while it can also result from interfacial vorticity production associated with the ion cyclotron effect in Hall-MHD with a finite Larmor radius. The limiting flow behavior of a large ion-skin-depth is explored. To assess the accuracy and appropriateness of the incompressible model, its ideal MHD predictions are compared to the results of the corresponding shock-driven nonlinear compressible simulations.", "date": "2020-06", "date_type": "published", "publication": "Physics of Plasmas", "volume": "27", "number": "6", "publisher": "American Institute of Physics", "pagerange": "Art. No. 062101", "id_number": "CaltechAUTHORS:20200608-115355282", "issn": "1070-664X", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200608-115355282", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "King Abdullah University of Science and Technology (KAUST)", "grant_number": "URF/1/3418-01" }, { "agency": "Australian Research Counci", "grant_number": "DE120102942" }, { "agency": "Australian Research Council", "grant_number": "DP120102378" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.5142042", "primary_object": { "basename": "1.5142042.pdf", "url": "https://authors.library.caltech.edu/records/dy8pc-mtz79/files/1.5142042.pdf" }, "resource_type": "article", "pub_year": "2020", "author_list": "Shen, Naijian; Wheatley, Vincent; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/ecd02-rgm88", "eprint_id": 102744, "eprint_status": "archive", "datestamp": "2023-08-19 21:24:52", "lastmod": "2023-10-20 00:27:56", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Cheng-Wan", "name": { "family": "Cheng", "given": "W." }, "orcid": "0000-0003-3960-4162" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Samtaney-Ravi", "name": { "family": "Samtaney", "given": "R." }, "orcid": "0000-0002-4702-6473" } ] }, "title": "Large-eddy simulation and modelling of Taylor\u2013Couette flow", "ispublished": "pub", "full_text_status": "public", "keywords": "turbulence modelling, turbulence simulation", "note": "\u00a9 The Author(s), 2020. Published by Cambridge University Press. \n\nReceived 12 August 2019; revised 18 January 2020; accepted 30 January 2020. Published online by Cambridge University Press: 12 March 2020. \n\nThis work was partially supported by the KAUST baseline research funds of R.S. The Cray XC40, Shaheen, at KAUST was utilized for all the reported LES. The authors gratefully acknowledge helpful comments from B. McKeon and N. Hutchins. \n\nThe authors report no conflict of interest.\n\nSubmitted - 1908.06577.pdf
", "abstract": "Wall-resolved large-eddy simulations (LES) of the incompressible Navier\u2013Stokes equations together with empirical modelling for turbulent Taylor\u2013Couette (TC) flow are presented. LES were performed with the inner cylinder rotating at angular velocity \u03a9_i and the outer cylinder stationary. With R_i, R_\u2080 the inner and outer radii respectively, the radius ratio is \u03b7 = 0.909 . The subgrid-scale stresses are represented using the stretched-vortex subgrid-scale model while the flow is resolved close to the wall. LES is implemented in the range Re_i = 10\u2075-10\u2076 where Re_i = \u03a9_iR_id/v and d = R\u2080-R_i is the cylinder gap. It is shown that the LES can capture the salient features of the flow, including the quantitative behaviour of spanwise Taylor rolls, the log variation in the inner-cylinder mean-velocity profile and the angular momentum redistribution due to the presence of Taylor rolls. A simple empirical model is developed for the turbulent, TC flow for both a stationary outer cylinder and also for co-rotating cylinders. This consists of near-wall, log-like turbulent wall layers separated by an annulus of constant angular momentum. Model results include the Nusselt number Nu (torque required to maintain the flow) and measures of the wall-layer thickness as functions of both the Taylor number Ta and \u03b7. These are compared with results from measurement, direct numerical simulation and the LES. A model extension to rough-wall turbulent flow is described. This shows an asymptotic, fully rough-wall state where the torque is independent of Re_i/Ta, and where Nu ~ Ta^(1/2).", "date": "2020-05-10", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "890", "publisher": "Cambridge University Press", "pagerange": "Art. No. A17", "id_number": "CaltechAUTHORS:20200423-101015762", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200423-101015762", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "King Abdullah University of Science and Technology (KAUST)" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/jfm.2020.101", "primary_object": { "basename": "1908.06577.pdf", "url": "https://authors.library.caltech.edu/records/ecd02-rgm88/files/1908.06577.pdf" }, "resource_type": "article", "pub_year": "2020", "author_list": "Cheng, W.; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/n5tdr-h2t42", "eprint_id": 99236, "eprint_status": "archive", "datestamp": "2023-08-19 18:05:47", "lastmod": "2023-10-18 17:59:50", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Shen-Naijian", "name": { "family": "Shen", "given": "Naijian" }, "orcid": "0000-0002-0533-8081" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Wheatley-V", "name": { "family": "Wheatley", "given": "Vincent" } }, { "id": "Samtaney-Ravi", "name": { "family": "Samtaney", "given": "Ravi" }, "orcid": "0000-0002-4702-6473" } ] }, "title": "Impulse-driven Richtmyer-Meshkov instability in Hall-magnetohydrodynamics", "ispublished": "pub", "full_text_status": "public", "note": "\u00a9 2019 American Physical Society. \n\nReceived 30 July 2019; published 11 October 2019. \n\nThis work was supported by the KAUST Office of Sponsored Research under Award No. URF/1/3418-01.\n\nPublished - PhysRevFluids.4.103902.pdf
", "abstract": "We utilize the incompressible, Hall-magnetohydrodynamics (MHD) model for conducting fluids to investigate the effect of Hall current on the stability of an impulsively accelerated, perturbed density interface, or contact discontinuity (CD) separating two fluids in the presence of a background magnetic field. This is used as a simple model, in a conducting fluid, of a Richtmyer-Meshkov type flow that is characterized in a neutral fluid by a shock-wave-density-interface interaction. Two versions of the Hall-MHD equations are explored. In the first, the ions are treated as an incompressible fluid but the electron gas retains its compressibility, while for the second version the incompressible limit for both species is invoked. The linearized equations of motion are first formulated for a sinusoidal interface perturbation and then solved as an initial-value problem using a Laplace transform method with general numerical inversion but with analytical inversion for some limiting-parameter cases. While the field equations are identical for both Hall-MHD models, the CD-jump conditions differ leading to qualitatively similar but quantitatively different CD dynamics. For both models, the presence of the magnetic field is found to suppress the incipient interfacial growth associated with neutral-gas, Richtmyer-Meshkov instability (RMI). When the ion skin depth is finite, the vorticity dynamics that drive the suppression of the RMI differ markedly from the ideal MHD, RMI flow. On the interface, the Hall-MHD description allows the presence of a tangential slip velocity which leads to finite circulation deposition. Away from the interface, vorticity is produced by the perturbed magnetic fields and transported to infinity by a dispersive wave system. This leads to decay of the velocity slip at the interface with the effect that interface growth remains bounded but distorted by damped oscillations associated with the ion cyclotron effect. The flow behavior for several limits of the ion skin depth and the Larmor radius is explored. Specific comparisons with the results from both models against ideal MHD are presented.", "date": "2019-10", "date_type": "published", "publication": "Physical Review Fluids", "volume": "4", "number": "10", "publisher": "American Physical Society", "pagerange": "Art. No. 103902", "id_number": "CaltechAUTHORS:20191011-104655515", "issn": "2469-990X", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20191011-104655515", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "King Abdullah University of Science and Technology (KAUST)", "grant_number": "URF/1/3418-01" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1103/physrevfluids.4.103902", "primary_object": { "basename": "PhysRevFluids.4.103902.pdf", "url": "https://authors.library.caltech.edu/records/n5tdr-h2t42/files/PhysRevFluids.4.103902.pdf" }, "resource_type": "article", "pub_year": "2019", "author_list": "Shen, Naijian; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/ynjqg-46v08", "eprint_id": 97544, "eprint_status": "archive", "datestamp": "2023-08-22 02:30:44", "lastmod": "2023-10-18 16:04:20", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Ferrer-E", "name": { "family": "Ferrer", "given": "E." }, "orcid": "0000-0003-1519-0444" }, { "id": "Saito-Namiko", "name": { "family": "Saito", "given": "N." } }, { "id": "Blackburn-H-M", "name": { "family": "Blackburn", "given": "H. M." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "High-Reynolds-number wall-modelled large eddy simulations of turbulent pipe flows using explicit and implicit subgrid stress treatments within a spectral element solver", "ispublished": "pub", "full_text_status": "public", "keywords": "Turbulent pipe flow; Large eddy simulation; Stretched-vortex model; Chung & Pullin model; Spectral vanishing viscosity (SVV); Wall model; Virtual-wall model", "note": "\u00a9 2019 Elsevier Ltd. \n\nReceived 3 September 2018, Revised 23 June 2019, Accepted 15 July 2019, Available online 31 July 2019.\n\nThe first author would like to thank financial support financial support from the project \"Estancias de movilidad en el extranjero Jos\u00e9 Castillejo para j\u00f3venes doctores\" (reference JC2015-00023) of the Spanish \"Ministerio de Educaci\u00f3n\". Additionally, the authors acknowledge the computer resources and technical assistance provided by the Centro de Supercomputaci\u00f3n y Visualizaci\u00f3n de Madrid (CeSViMa).\n\nSubmitted - High-Reynolds-number_wall-modelled_large.pdf
", "abstract": "We present explicit and implicit large eddy simulations for fully developed turbulent pipe flows using a continuous-Galerkin spectral element solver. On the one hand, the explicit stretched-vortex model (by Misra & Pullin [45] and Chung & Pullin [14]), accounts for an explicit treatment of unresolved stresses and is adapted to the high-order solver. On the other hand, an implicit approach based on a spectral vanishing viscosity technique is implemented. The latter implicit technique is modified to incorporate Chung & Pullin virtual-wall model instead of relying on implicit dissipative mechanisms near walls. This near-wall model is derived by averaging in the wall-normal direction and relying in local inner scaling to treat the time-dependence of the filtered wall-parallel velocity. The model requires space-time varying Dirichlet and Neumann boundary conditions for velocity and pressure respectively. We provide results and comparisons for the explicit and implicit subgrid treatments and show that both provide favourable results for pipe flows at Re_\u03c4 = 2\u00d710^3 and Re_\u03c4 = 1.8\u00d710^5 in terms of turbulence statistics. Additionally, we conclude that implicit simulations are enhanced when including the wall model and provide the correct statistics near walls.", "date": "2019-09-15", "date_type": "published", "publication": "Computers & Fluids", "volume": "191", "publisher": "Elsevier", "pagerange": "Art. No. 104239", "id_number": "CaltechAUTHORS:20190731-090901303", "issn": "0045-7930", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190731-090901303", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Ministerio de Educacion y Ciencia (MEC)", "grant_number": "JC2015-00023" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1016/j.compfluid.2019.104239", "primary_object": { "basename": "High-Reynolds-number_wall-modelled_large.pdf", "url": "https://authors.library.caltech.edu/records/ynjqg-46v08/files/High-Reynolds-number_wall-modelled_large.pdf" }, "resource_type": "article", "pub_year": "2019", "author_list": "Ferrer, E.; Saito, N.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/5x4kk-fqr83", "eprint_id": 91094, "eprint_status": "archive", "datestamp": "2023-08-19 13:50:43", "lastmod": "2023-10-19 22:08:30", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Braun-N-O", "name": { "family": "Braun", "given": "N. O." }, "orcid": "0000-0002-9710-0686" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Meiron-D-I", "name": { "family": "Meiron", "given": "D. I." }, "orcid": "0000-0003-0397-3775" } ] }, "title": "Large eddy simulation investigation of the canonical shock\u2013turbulence interaction", "ispublished": "pub", "full_text_status": "restricted", "keywords": "compressible turbulence, shock waves, turbulence modelling", "note": "\u00a9 2018 Cambridge University Press. \n\n(Received 15 December 2017; revised 28 August 2018; accepted 20 September 2018) \n\nThis work was supported under Los Alamos National Laboratory (LANL) contract number 74372-001-09. This work used the Extreme Science and Engineering Discovery Environment (XSEDE) (Towns et al. 2014), which is supported by National Science Foundation grant number ACI-1053575. The authors would also like to thank D. Livescu of Los Alamos National Laboratory for providing parts of the linear analysis code used in this document.", "abstract": "High resolution large eddy simulations (LES) are performed to study the interaction of a stationary shock with fully developed turbulent flow. Turbulent statistics downstream of the interaction are provided for a range of weakly compressible upstream turbulent Mach numbers M_t = 0.03\u22120.18, shock Mach numbers M_s = 1.2\u22123.0 and Taylor-based Reynolds numbers Re_\u03bb = 20\u22122500. The LES displays minimal Reynolds number effects once an inertial range has developed for Re_\u03bb > 100. The inertial range scales of the turbulence are shown to quickly return to isotropy, and downstream of sufficiently strong shocks this process generates a net transfer of energy from transverse into streamwise velocity fluctuations. The streamwise shock displacements are shown to approximately follow a k^(\u221211/3) decay with wavenumber as predicted by linear analysis. In conjunction with other statistics this suggests that the instantaneous interaction of the shock with the upstream turbulence proceeds in an approximately linear manner, but nonlinear effects immediately downstream of the shock significantly modify the flow even at the lowest considered turbulent Mach numbers.", "date": "2019-01-10", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "858", "publisher": "Cambridge University Press", "pagerange": "500-535", "id_number": "CaltechAUTHORS:20181120-151734295", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181120-151734295", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Los Alamos National Laboratory", "grant_number": "74372-001-09" }, { "agency": "NSF", "grant_number": "ACI-1053575" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/jfm.2018.766", "resource_type": "article", "pub_year": "2019", "author_list": "Braun, N. O.; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/753cc-e3s78", "eprint_id": 91976, "eprint_status": "archive", "datestamp": "2023-08-19 13:01:59", "lastmod": "2023-10-23 15:47:37", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Shen-Naijian", "name": { "family": "Shen", "given": "Naijian" }, "orcid": "0000-0002-0533-8081" }, { "id": "Li-Yuan", "name": { "family": "Li", "given": "Yuan" }, "orcid": "0000-0003-2865-4877" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Samtaney-Ravi", "name": { "family": "Samtaney", "given": "Ravi" }, "orcid": "0000-0002-4702-6473" }, { "id": "Wheatley-V", "name": { "family": "Wheatley", "given": "Vincent" } } ] }, "title": "On the magnetohydrodynamic limits of the ideal two-fluid plasma equations", "ispublished": "pub", "full_text_status": "public", "note": "\u00a9 2018 AIP Publishing. \n\n(Received 17 October 2018; accepted 2 December 2018; published online 26 December 2018) \n\nThis work was supported by the KAUST Office of Sponsored Research under Award No. URF/1/3418-01.\n\nPublished - 1.5067387.pdf
Erratum - 1.5094930.pdf
", "abstract": "The two-fluid plasma equations describing a magnetized plasma, originating from truncating moments of the Vlasov-Boltzmann equation, are increasingly used to describe an ion-electron plasma whose transport phenomena occur on a time scale slower and a length scale longer than those of particle collisions. A similar treatment under more stringent constraints gives the single-fluid magnetohydrodynamic (MHD) equations for low-frequency macroscopic processes. Since both stem from kinetic theory, the two-fluid plasma and MHD equations are necessarily related to each other. Such a connection is often established via ad hoc physical reasoning without a firm analytical foundation. Here, we perform a sequence of formal expansions for the dimensionless ideal two-fluid plasma equations with respect to limiting values of the speed-of-light c, the ion-to-electron mass ratio M, and the plasma skin depth d_S. Several different closed systems of equations result, including separate systems for each limit applied in isolation and those resulting from limits applied in combination, which correspond to the well-known Hall-MHD and single-fluid ideal MHD equations. In particular, it is shown that while the zeroth-order description corresponding to the c\u2192\u221e limit, with M and dS fixed, is strictly charge neutral, it nonetheless uniquely determines the perturbation charge non-neutrality at the first order. Furthermore, the additional M\u2192\u221e limit is found to be not required to obtain the single-fluid MHD equations despite being essential for the Hall-MHD system. The hierarchy of systems presented demonstrates how plasmas can be appropriately modeled in situations where only one of the limits applies, which lie in the parameter space in between where the two-fluid plasma and Hall-MHD models are appropriate.", "date": "2018-12", "date_type": "published", "publication": "Physics of Plasmas", "volume": "25", "number": "12", "publisher": "American Institute of Physics", "pagerange": "Art. No. 122113", "id_number": "CaltechAUTHORS:20190102-092233851", "issn": "1070-664X", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190102-092233851", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "King Abdullah University of Science and Technology (KAUST)", "grant_number": "URF/1/3418-01" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.5067387", "primary_object": { "basename": "1.5067387.pdf", "url": "https://authors.library.caltech.edu/records/753cc-e3s78/files/1.5067387.pdf" }, "related_objects": [ { "basename": "1.5094930.pdf", "url": "https://authors.library.caltech.edu/records/753cc-e3s78/files/1.5094930.pdf" } ], "resource_type": "article", "pub_year": "2018", "author_list": "Shen, Naijian; Li, Yuan; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/166a3-rxq89", "eprint_id": 90164, "eprint_status": "archive", "datestamp": "2023-08-22 00:20:30", "lastmod": "2023-10-18 23:15:12", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Cheng-Wan", "name": { "family": "Cheng", "given": "W." }, "orcid": "0000-0003-3960-4162" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Samtaney-Ravi", "name": { "family": "Samtaney", "given": "R." }, "orcid": "0000-0002-4702-6473" } ] }, "title": "Large-eddy simulation of flow over a rotating cylinder: the lift crisis at Re_D = 6 \u00d7 10^4", "ispublished": "pub", "full_text_status": "restricted", "keywords": "Boundary Layers: Boundary layer separation; Boundary Layers: Boundary Layers; Turbulent Flows: Turbulence simulation", "note": "\u00a9 2018 Cambridge University Press. \n\nReceived 22 February 2018; revised 28 June 2018; accepted 5 August 2018; first published online 19 September 2018. \n\nThis work was partially supported by the KAUST baseline research funds of R.S. The Cray XC40, Shaheen, at KAUST was utilized for all the reported LES.", "abstract": "We present wall-resolved large-eddy simulation (LES) of flow with free-stream velocity U\u221e over a cylinder of diameter D rotating at constant angular velocity \u03a9, with the focus on the lift crisis, which takes place at relatively high Reynolds number Re_D = U\u221eD/\u03bd, where \u03bd is the kinematic viscosity of the fluid. Two sets of LES are performed within the (ReD, \u03b1)-plane with \u03b1 = \u03a9D/(2U\u221e) the dimensionless cylinder rotation speed. One set, at Re_D = 5000, is used as a reference flow and does not exhibit a lift crisis. Our main LES varies \u03b1 in 0 \u2a7d \u03b1 \u2a7d 2.0 at fixed Re_D = 6\u00d710^4. For \u03b1 in the range \u03b1 = 0.48\u22120.6 we find a lift crisis. This range is in agreement with experiment although the LES shows a deeper local minimum in the lift coefficient than the measured value. Diagnostics that include instantaneous surface portraits of the surface skin-friction vector field C_f, spanwise-averaged flow-streamline plots, and a statistical analysis of local, near-surface flow reversal show that, on the leeward-bottom cylinder surface, the flow experiences large-scale reorganization as \u03b1 increases through the lift crisis. At \u03b1 = 0.48 the primary-flow features comprise a shear layer separating from that side of the cylinder that moves with the free stream and a pattern of oscillatory but largely attached flow zones surrounded by scattered patches of local flow separation/reattachment on the lee and underside of the cylinder surface. Large-scale, unsteady vortex shedding is observed. At \u03b1 = 0.6 the flow has transitioned to a more ordered state where the small-scale separation/reattachment cells concentrate into a relatively narrow zone with largely attached flow elsewhere. This induces a low-pressure region which produces a sudden decrease in lift and hence the lift crisis. Through this process, the boundary layer does not show classical turbulence behaviour. As \u03b1 is further increased at constant Re_D, the localized separation zone dissipates with corresponding attached flow on most of the cylinder surface. The lift coefficient then resumes its increasing trend. A logarithmic region is found within the boundary layer at \u03b1 = 1.0.", "date": "2018-11-25", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "855", "publisher": "Cambridge University Press", "pagerange": "371-407", "id_number": "CaltechAUTHORS:20181008-151606899", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181008-151606899", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "King Abdullah University of Science and Technology (KAUST)" } ] }, "doi": "10.1017/jfm.2018.644", "resource_type": "article", "pub_year": "2018", "author_list": "Cheng, W.; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/gstm8-1nr09", "eprint_id": 88470, "eprint_status": "archive", "datestamp": "2023-08-19 10:42:51", "lastmod": "2023-10-18 22:05:23", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Summy-D-P", "name": { "family": "Summy", "given": "D. P." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "On the Five-Moment Hamburger Maximum Entropy Reconstruction", "ispublished": "pub", "full_text_status": "restricted", "keywords": "Maximum entropy closure \u00b7 Moments \u00b7 Five-moment reconstruction", "note": "\u00a9 Springer Science+Business Media 2018. \n\nReceived: 25 September 2017 / Accepted: 6 April 2018 / Published online: 14 May 2018. \n\nThis research was partially supported by the National Science Foundation under Award Number: DMS-1418903.", "abstract": "We consider the Maximum Entropy Reconstruction (MER) as a solution to the five-moment truncated Hamburger moment problem in one dimension. In the case of five monomial moment constraints, the probability density function (PDF) of the MER takes the form of the exponential of a quartic polynomial. This implies a possible bimodal structure in regions of moment space. An analytical model is developed for the MER PDF applicable near a known singular line in a centered, two-component, third- and fourth-order moment (\u03bc_3, \u03bc_4) space, consistent with the general problem of five moments. The model consists of the superposition of a perturbed, centered Gaussian PDF and a small-amplitude packet of PDF-density, called the outlying moment packet (OMP), sitting far from the mean. Asymptotic solutions are obtained which predict the shape of the perturbed Gaussian and both the amplitude and position on the real line of the OMP. The asymptotic solutions show that the presence of the OMP gives rise to an MER solution that is singular along a line in ( \u03bc_3, \u03bc_4) space emanating from, but not including, the point representing a standard normal distribution, or thermodynamic equilibrium. We use this analysis of the OMP to develop a numerical regularization of the MER, creating a procedure we call the Hybrid MER (HMER). Compared with the MER, the HMER is a significant improvement in terms of robustness and efficiency while preserving accuracy in its prediction of other important distribution features, such as higher order moments.", "date": "2018-08", "date_type": "published", "publication": "Journal of Statistical Physics", "volume": "172", "number": "3", "publisher": "Springer", "pagerange": "854-879", "id_number": "CaltechAUTHORS:20180801-140416478", "issn": "0022-4715", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180801-140416478", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF", "grant_number": "DMS-1418903" } ] }, "local_group": { "items": [ { "id": "GALCIT" }, { "id": "Graduate-Aeronautical-Laboratories-(Fluid-Mechanics)" } ] }, "doi": "10.1007/s10955-018-2034-9", "resource_type": "article", "pub_year": "2018", "author_list": "Summy, D. P. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/2q03g-82y29", "eprint_id": 88121, "eprint_status": "archive", "datestamp": "2023-08-19 10:33:54", "lastmod": "2023-10-18 21:48:33", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Mostert-W", "name": { "family": "Mostert", "given": "W." }, "orcid": "0000-0001-6251-4136" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Samtaney-Ravi", "name": { "family": "Samtaney", "given": "R." }, "orcid": "0000-0002-4702-6473" }, { "id": "Wheatley-V", "name": { "family": "Wheatley", "given": "V." } } ] }, "title": "Spontaneous singularity formation in converging cylindrical shock waves", "ispublished": "pub", "full_text_status": "public", "note": "\u00a9 2018 American Physical Society. \n\nReceived 28 March 2018; published 23 July 2018. \n\nThis research was supported by the KAUST Office of Sponsored Research under Award No. URF/1/2162-01.\n\nPublished - PhysRevFluids.3.071401.pdf
", "abstract": "We develop a nonlinear, Fourier-based analysis of the evolution of a perturbed, converging cylindrical strong shock using the approximate method of geometrical shock dynamics (GSD). This predicts that a singularity in the shock-shape geometry, corresponding to a change in Fourier-coefficient decay from exponential to algebraic, is guaranteed to form prior to the time of shock impact at the origin, for arbitrarily small, finite initial perturbation amplitude. Specifically for an azimuthally periodic Mach-number perturbation on an initially circular shock with integer mode number q and amplitude proportional to \u03b5\u226a1, a singularity in the shock geometry forms at a mean shock radius R_(u,c)\u223c(q^2\u03b5)^(\u22121/b1), where b_1(\u03b3)<0 is a derived constant and \u03b3 the ratio of specific heats. This requires q^2\u03b5\u226a1, q\u226b1. The constant of proportionality is obtained as a function of \u03b3 and is independent of the initial shock Mach number M0. Singularity formation corresponds to the transition from a smooth perturbation to a faceted polygonal form. Results are qualitatively verified by a numerical GSD comparison.", "date": "2018-07-23", "date_type": "published", "publication": "Physical Review Fluids", "volume": "3", "number": "7", "publisher": "American Physical Society", "pagerange": "Art. No. 071401", "id_number": "CaltechAUTHORS:20180723-095359785", "issn": "2469-990X", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180723-095359785", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "King Abdullah University of Science and Technology (KAUST)", "grant_number": "URF/1/2162-01" } ] }, "local_group": { "items": [ { "id": "GALCIT" }, { "id": "Graduate-Aeronautical-Laboratories-(Fluid-Mechanics)" } ] }, "doi": "10.1103/PhysRevFluids.3.071401", "primary_object": { "basename": "PhysRevFluids.3.071401.pdf", "url": "https://authors.library.caltech.edu/records/2q03g-82y29/files/PhysRevFluids.3.071401.pdf" }, "resource_type": "article", "pub_year": "2018", "author_list": "Mostert, W.; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/2jd9g-za261", "eprint_id": 88843, "eprint_status": "archive", "datestamp": "2023-08-21 23:40:57", "lastmod": "2023-10-18 22:21:00", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Mostert-W", "name": { "family": "Mostert", "given": "W." }, "orcid": "0000-0001-6251-4136" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Samtaney-Ravi", "name": { "family": "Samtaney", "given": "R." }, "orcid": "0000-0002-4702-6473" }, { "id": "Wheatley-V", "name": { "family": "Wheatley", "given": "V." } } ] }, "title": "Singularity formation on perturbed planar shock waves", "ispublished": "pub", "full_text_status": "restricted", "keywords": "Compressible Flows: Compressible Flows; Compressible Flows: Shock waves", "note": "\u00a9 2018 Cambridge University Press. \n\nReceived 28 June 2017; revised 7 March 2018; accepted 16 March 2018; first published online 8 May 2018. Published online: 08 May 2018. \n\nThis research was supported by the KAUST Office of Sponsored Research under award URF/1/2162-01.", "abstract": "We present an analysis that predicts the time to development of a singularity in the shape profile of a spatially periodic perturbed, planar shock wave for ideal gas dynamics. Beginning with a formulation in complex coordinates of Whitham's approximate model geometrical shock dynamics (GSD), we apply a spectral treatment to derive the asymptotic form for the leading-order behaviour of the shock Fourier coefficients for large mode numbers and time. This is shown to determine a critical time at which the coefficients begin to decay, with respect to mode number, at an algebraic rate with an exponent of -5/2, indicating loss of analyticity and the formation of a singularity in the shock geometry. The critical time is found to be inversely proportional to a representative measure of perturbation amplitude \u03f5 with an explicit analytic form for the constant of proportionality in terms of gas and shock parameters. To leading order, the time to singularity formation is dependent only on the first Fourier mode. Comparison with results of numerical solutions to the full GSD equations shows that the predicted critical time somewhat underestimates the time for shock\u2013shock (triple-point) formation, where the latter is obtained by post-processing the numerical GSD results using an edge-detection algorithm. Aspects of the analysis suggest that the appearance of loss of analyticity in the shock surface may be a precursor to the first appearance of shock\u2013shocks, which may account for part of the discrepancy. The frequency of oscillation of the shock perturbation is accurately predicted. In addition, the analysis is extended to the evolution of a perturbed planar, fast magnetohydrodynamic shock for the case when the external magnetic field is aligned parallel to the unperturbed shock. It is found that, for a strong shock, the presence of the magnetic field produces only a higher-order correction to the GSD equations with the result that the time to loss of analyticity is the same as for the gas-dynamic flow. Limitations and improvements for the analysis are discussed, as are comparisons with the analogous appearance of singularity formation in vortex-sheet evolution in an incompressible inviscid fluid.", "date": "2018-07-10", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "846", "publisher": "Cambridge University Press", "pagerange": "536-562", "id_number": "CaltechAUTHORS:20180816-081505294", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180816-081505294", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "King Abdullah University of Science and Technology (KAUST)", "grant_number": "URF/1/2162-01" } ] }, "local_group": { "items": [ { "id": "GALCIT" }, { "id": "Graduate-Aeronautical-Laboratories-(Fluid-Mechanics)" } ] }, "doi": "10.1017/jfm.2018.263", "resource_type": "article", "pub_year": "2018", "author_list": "Mostert, W.; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/tqtak-cdh27", "eprint_id": 84825, "eprint_status": "archive", "datestamp": "2023-08-21 23:21:08", "lastmod": "2023-10-18 16:43:50", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Braun-N-O", "name": { "family": "Braun", "given": "N. O." }, "orcid": "0000-0002-9710-0686" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Meiron-D-I", "name": { "family": "Meiron", "given": "D. I." }, "orcid": "0000-0003-0397-3775" } ] }, "title": "Regularization method for large eddy simulations of shock-turbulence interactions", "ispublished": "pub", "full_text_status": "restricted", "keywords": "Compressible turbulence; Shockwaves; LES; Hyperviscosity", "note": "\u00a9 2018 Elsevier Inc. \n\nReceived 6 April 2017, Revised 10 January 2018, Accepted 30 January 2018, Available online 13 February 2018. \n\nThis work was supported under Los Alamos National Laboratory contract number 74372-001-09, and the Extreme Science and Engineering Discovery Environment (XSEDE) [46], which is supported by National Science Foundation grant number ACI-1053575.", "abstract": "The rapid change in scales over a shock has the potential to introduce unique difficulties in Large Eddy Simulations (LES) of compressible shock-turbulence flows if the governing model does not sufficiently capture the spectral distribution of energy in the upstream turbulence. A method for the regularization of LES of shock-turbulence interactions is presented which is constructed to enforce that the energy content in the highest resolved wavenumbers decays as k^(\u22125/3), and is computed locally in physical-space at low computational cost. The application of the regularization to an existing subgrid scale model is shown to remove high wavenumber errors while maintaining agreement with Direct Numerical Simulations (DNS) of forced and decaying isotropic turbulence. Linear interaction analysis is implemented to model the interaction of a shock with isotropic turbulence from LES. Comparisons to analytical models suggest that the regularization significantly improves the ability of the LES to predict amplifications in subgrid terms over the modeled shockwave. LES and DNS of decaying, modeled post shock turbulence are also considered, and inclusion of the regularization in shock-turbulence LES is shown to improve agreement with lower Reynolds number DNS.", "date": "2018-05-15", "date_type": "published", "publication": "Journal of Computational Physics", "volume": "361", "publisher": "Elsevier", "pagerange": "231-246", "id_number": "CaltechAUTHORS:20180214-082550535", "issn": "0021-9991", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180214-082550535", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Los Alamos National Laboratory", "grant_number": "74372-001-09" }, { "agency": "NSF", "grant_number": "ACI-1053575" } ] }, "local_group": { "items": [ { "id": "GALCIT" }, { "id": "Graduate-Aeronautical-Laboratories-(Fluid-Mechanics)" } ] }, "doi": "10.1016/j.jcp.2018.01.052", "resource_type": "article", "pub_year": "2018", "author_list": "Braun, N. O.; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/qj1vy-vv233", "eprint_id": 83933, "eprint_status": "archive", "datestamp": "2023-08-19 07:28:26", "lastmod": "2023-10-18 14:31:44", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Cheng-Wan", "name": { "family": "Cheng", "given": "W." }, "orcid": "0000-0003-3960-4162" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Samtaney-Ravi", "name": { "family": "Samtaney", "given": "R." }, "orcid": "0000-0002-4702-6473" } ] }, "title": "Large-eddy simulation of flow over a grooved cylinder up to transcritical Reynolds numbers", "ispublished": "pub", "full_text_status": "restricted", "keywords": "boundary layer separation, turbulence simulation, turbulent flows", "note": "\u00a9 2017 Cambridge University Press. \n\n(Received 5 July 2017; revised 12 September 2017; accepted 18 October 2017) Published online: 27 November 2017. \n\nThis work was partially supported by the KAUST baseline research funds of R.S. The Cray XC40, Shaheen, at KAUST was utilized for all the reported LES.", "abstract": "We report wall-resolved large-eddy simulation (LES) of flow over a grooved cylinder up to the transcritical regime. The stretched-vortex subgrid-scale model is embedded in a general fourth-order finite-difference code discretization on a curvilinear mesh. In the present study grooves are equally distributed around the circumference of the cylinder, each of sinusoidal shape with height \u03b5, invariant in the spanwise direction. Based on the two parameters, \u03b5/D and the Reynolds number Re_D = U_\u221eD/\u03bd where U_\u221e is the free-stream velocity, D the diameter of the cylinder and \u03bd the kinematic viscosity, two main sets of simulations are described. The first set varies from 0 to 1/32 while fixing Re_D = 3.9 x 10^3. We study the flow deviation from the smooth-cylinder case, with emphasis on several important statistics such as the length of the mean-flow recirculation bubble L_B, the pressure coefficient C_P, the skin-friction coefficient C_f\u03b8 and the non-dimensional pressure gradient parameter \u03b2. It is found that, with increasing \u03b5/D at fixed Re_D , some properties of the mean flow behave somewhat similarly to changes in the smooth-cylinder flow when Re_D is increased. This includes shrinking L_B and nearly constant minimum pressure coefficient. In contrast, while the non-dimensional pressure gradient parameter \u03b2 remains nearly constant for the front part of the smooth cylinder flow, \u03b2 shows an oscillatory variation for the grooved-cylinder case. The second main set of LES varies Re_D from 3.9 x 10^3 to 6 x 10^4 with fixed \u03b5/D = 1/32. It is found that this Re_D range spans the subcritical and supercritical regimes and reaches the beginning of the transcritical flow regime. Mean-flow properties are diagnosed and compared with available experimental data including C_P and the drag coefficient C_D. The timewise variation of the lift and drag coefficients are also studied to elucidate the transition among three regimes. Instantaneous images of the surface, skin-friction vector field and also of the three-dimensional Q-criterion field are utilized to further understand the dynamics of the near-surface flow structures and vortex shedding. Comparison of the grooved-cylinder flow with the equivalent flow over a smooth-wall cylinder shows structural similarities but significant differences. Both flows exhibit a clear common signature, which is the formation of mean-flow secondary separation bubbles that transform to other local flow features upstream of the main separation region (prior separation bubbles) as is increased through the respective drag crises. Based on these similarities it is hypothesized that the drag crises known to occur for flow past a cylinder with different surface topographies is the result of a change in the global flow state generated by an interaction of primary flow separation with secondary flow recirculating motions that manifest as a mean-flow secondary bubble. For the smooth-wall flow this is accompanied by local boundary-layer flow transition to turbulence and a strong drag crisis, while for the grooved-cylinder case the flow remains laminar but unsteady through its drag crisis and into the early transcritical flow range.", "date": "2018-01-25", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "835", "publisher": "Cambridge University Press", "pagerange": "327-362", "id_number": "CaltechAUTHORS:20171214-160643790", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20171214-160643790", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "King Abdullah University of Science and Technology (KAUST)" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/jfm.2017.767", "resource_type": "article", "pub_year": "2018", "author_list": "Cheng, W.; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/xqph5-g5070", "eprint_id": 83254, "eprint_status": "archive", "datestamp": "2023-08-19 07:00:22", "lastmod": "2023-10-17 23:00:44", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Bond-D", "name": { "family": "Bond", "given": "D." }, "orcid": "0000-0001-5261-3720" }, { "id": "Wheatley-V", "name": { "family": "Wheatley", "given": "V." } }, { "id": "Samtaney-Ravi", "name": { "family": "Samtaney", "given": "R." }, "orcid": "0000-0002-4702-6473" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Richtmyer\u2013Meshkov instability of a thermal interface in a two-fluid plasma", "ispublished": "pub", "full_text_status": "restricted", "keywords": "instability, MHD and electrohydrodynamics", "note": "\u00a9 2017 Cambridge University Press. \n\nReceived 29 November 2016; revised 24 September 2017; accepted 25 September 2017. \n\nThis research was supported by the KAUST Office of Sponsored Research under Award URF/1/2162-01. This work was supported by computational resources provided by the Australian Government under the National Computational Merit Allocation Scheme.", "abstract": "We computationally investigate the Richtmyer\u2013Meshkov instability of a density interface with a single-mode perturbation in a two-fluid, ion\u2013electron plasma with no initial magnetic field. Self-generated magnetic fields arise subsequently. We study the case where the density jump across the initial interface is due to a thermal discontinuity, and select plasma parameters for which two-fluid plasma effects are expected to be significant in order to elucidate how they alter the instability. The instability is driven via a Riemann problem generated precursor electron shock that impacts the density interface ahead of the ion shock. The resultant charge separation and motion generates electromagnetic fields that cause the electron shock to degenerate and periodically accelerate the electron and ion interfaces, driving Rayleigh\u2013Taylor instability. This generates small-scale structures and substantially increases interfacial growth over the hydrodynamic case.", "date": "2017-12-25", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "833", "publisher": "Cambridge University Press", "pagerange": "332-363", "id_number": "CaltechAUTHORS:20171116-111902831", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20171116-111902831", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "King Abdullah University of Science and Technology (KAUST)", "grant_number": "URF/1/2162-01" }, { "agency": "Australian Government" } ] }, "doi": "10.1017/jfm.2017.693", "resource_type": "article", "pub_year": "2017", "author_list": "Bond, D.; Wheatley, V.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/mbb2v-dx147", "eprint_id": 81023, "eprint_status": "archive", "datestamp": "2023-08-19 04:22:03", "lastmod": "2023-10-17 19:21:11", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Hutchins-N", "name": { "family": "Hutchins", "given": "N." } }, { "id": "Chung-Daniel", "name": { "family": "Chung", "given": "D." }, "orcid": "0000-0003-3732-364X" } ] }, "title": "Turbulent flow over a long flat plate with uniform roughness", "ispublished": "pub", "full_text_status": "public", "note": "\u00a9 2017 American Physical Society. \n\nReceived 7 March 2017; published 31 August 2017. \n\nThis research was supported under Australian Research Council's Discovery Projects funding scheme (Grant No. DP160102279) and partially by NSF Award No. CBET 1235605.\n\nPublished - PhysRevFluids.2.082601.pdf
", "abstract": "For turbulent boundary-layer flow under a uniform freestream speed U\u221e over a plate of length L, covered with uniform roughness of nominal sand-grain scale k_s, the physical behaviors underlying two distinguished limits at large Re_L\u2261U\u221eL/\u03bd are explored: the fully rough wall flow where k_s/L is fixed and the long-plate limit where Re_k\u2261U\u221ek_s/\u03bd is fixed. For the fully rough limit it is shown that not only is the drag coefficient C_D independent of Re_L but that a universal skin-friction coefficient C_f and normalized boundary-layer thickness \u03b4/k_s can be found that depends only on ks_/x, where x is the downstream distance. In the long-plate limit, it is shown that the flow becomes asymptotically smooth at huge Re_L at a rate that depends on Re_k. Comparisons with wind-tunnel and field data are made.", "date": "2017-08", "date_type": "published", "publication": "Physical Review Fluids", "volume": "2", "number": "8", "publisher": "American Physical Society", "pagerange": "Art. No. 082601", "id_number": "CaltechAUTHORS:20170831-132932417", "issn": "2469-990X", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170831-132932417", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Australian Research Council", "grant_number": "DP160102279" }, { "agency": "NSF", "grant_number": "CBET-1235605" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1103/PhysRevFluids.2.082601", "primary_object": { "basename": "PhysRevFluids.2.082601.pdf", "url": "https://authors.library.caltech.edu/records/mbb2v-dx147/files/PhysRevFluids.2.082601.pdf" }, "resource_type": "article", "pub_year": "2017", "author_list": "Pullin, D. I.; Hutchins, N.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/xvggv-mcb73", "eprint_id": 77907, "eprint_status": "archive", "datestamp": "2023-08-19 03:20:02", "lastmod": "2024-03-05 20:32:06", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Cheng-Wan", "name": { "family": "Cheng", "given": "W." }, "orcid": "0000-0003-3960-4162" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." }, "orcid": "0009-0007-5991-2863" }, { "id": "Samtaney-Ravi", "name": { "family": "Samtaney", "given": "R." }, "orcid": "0000-0002-4702-6473" }, { "id": "Zhang-W", "name": { "family": "Zhang", "given": "W." } }, { "id": "Gao-W", "name": { "family": "Gao", "given": "W." } } ] }, "title": "Large-eddy simulation of flow over a cylinder with Re_D from to 3.9 x 10^3 to 8.5 x 10^5: a skin-friction perspective", "ispublished": "pub", "full_text_status": "restricted", "note": "\u00a9 2017 Cambridge University Press. \n\nReceived 11 October 2016; revised 14 March 2017; accepted 14 March 2017; Published online: 05 May 2017. \n\nW.C. and R.S. were supported by the KAUST Office of Competitive Research Funds (OCRF) under award no. URF/1/1394-01. D.I.P. was partially supported under KAUST OCRF award no. URF/1/1394-01 and partially by NSF award CBET 1235605. The Cray XC40, Shaheen, at KAUST was utilized for all of the reported LES.", "abstract": "We present wall-resolved large-eddy simulations (LES) of flow over a smooth-wall circular cylinder up to Re_D = 8.5 \u00d7 10^5, where Re_D is Reynolds number based on the cylinder diameter D and the free-stream speed U_\u221e. The stretched-vortex subgrid-scale (SGS) model is used in the entire simulation domain. For the sub-critical regime, six cases are implemented with 3.9 \u00d7 10^3 \u2a7d Re_D \u2a7d 10^5. Results are compared with experimental data for both the wall-pressure-coefficient distribution on the cylinder surface, which dominates the drag coefficient, and the skin-friction coefficient, which clearly correlates with the separation behaviour. In the super-critical regime, LES for three values of Re_D are carried out at different resolutions. The drag-crisis phenomenon is well captured. For lower resolution, numerical discretization fluctuations are sufficient to stimulate transition, while for higher resolution, an applied boundary-layer perturbation is found to be necessary to stimulate transition. Large-eddy simulation results at Re_D = 8.5 \u00d7 10^5, with a mesh of 8192 \u00d7 1024 \u00d7 256, agree well with the classic experimental measurements of Achenbach (J. Fluid Mech., vol. 34, 1968, pp. 625\u2013639) especially for the skin-friction coefficient, where a spike is produced by the laminar\u2013turbulent transition on the top of a prior separation bubble. We document the properties of the attached-flow boundary layer on the cylinder surface as these vary with ReDReD . Within the separated portion of the flow, mean-flow separation\u2013reattachment bubbles are observed at some values of Re_D, with separation characteristics that are consistent with experimental observations. Time sequences of instantaneous surface portraits of vector skin-friction trajectory fields indicate that the unsteady counterpart of a mean-flow separation\u2013reattachment bubble corresponds to the formation of local flow-reattachment cells, visible as coherent bundles of diverging surface streamlines.", "date": "2017-06", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "820", "publisher": "Cambridge University Press", "pagerange": "121-158", "id_number": "CaltechAUTHORS:20170602-084638629", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170602-084638629", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "King Abdullah University of Science and Technology (KAUST)", "grant_number": "URF/1/1394-01" }, { "agency": "NSF", "grant_number": "CBET-1235605" } ] }, "collection": "CaltechAUTHORS", "doi": "10.1017/jfm.2017.172", "resource_type": "article", "pub_year": "2017", "author_list": "Cheng, W.; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/w1k2v-pq664", "eprint_id": 77062, "eprint_status": "archive", "datestamp": "2023-08-19 02:52:06", "lastmod": "2023-10-25 17:16:12", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Sridhar-Akshay", "name": { "family": "Sridhar", "given": "A." }, "orcid": "0000-0002-2642-8246" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Cheng-Wan", "name": { "family": "Cheng", "given": "W." }, "orcid": "0000-0003-3960-4162" } ] }, "title": "Rough-wall turbulent boundary layers with constant skin friction", "ispublished": "pub", "full_text_status": "restricted", "note": "\u00a9 2017 Cambridge University Press. \n\nReceived 9 June 2016; revised 23 February 2017; accepted 27 February 2017; first published online 28 March 2017. \n\nA.S. and D.I.P. were partially supported by the KAUST Office of Competitive Research Funds (OCRF) under award no. URF/1/1394-01 and partially by NSF award CBET 1235605. W.C. was supported by the KAUST OCRF under award no. URF/1/1394-01. The authors acknowledge helpful conversations with R. A. Antonia.", "abstract": "A semi-empirical model is presented that describes the development of a fully developed turbulent boundary layer in the presence of surface roughness with length scale k_s that varies with streamwise distance x. Interest is centred on flows for which all terms of the von K\u00e1rm\u00e1n integral relation, including the ratio of outer velocity to friction velocity U^+_\u221e\u2261U_\u221e/u_\u03c4, are streamwise constant. For Re_x assumed large, use is made of a simple log-wake model of the local turbulent mean-velocity profile that contains a standard mean-velocity correction for the asymptotic fully rough regime and with assumed constant parameter values. It is then shown that, for a general power-law external velocity variation U_\u221e\u223cx^m, all measures of the boundary-layer thickness must be proportional to x and that the surface sand-grain roughness scale variation must be the linear form k_s(x)=\u03b1x, where x is the distance from the boundary layer of zero thickness and \u03b1 is a dimensionless constant. This is shown to give a two-parameter (m,\u03b1) family of solutions, for which U^+_\u221e (or equivalently C_f) and boundary-layer thicknesses can be simply calculated. These correspond to perfectly self-similar boundary-layer growth in the streamwise direction with similarity variable z/(\u03b1x), where z is the wall-normal coordinate. Results from this model over a range of \u03b1 are discussed for several cases, including the zero-pressure-gradient (m=0) and sink-flow (m=\u22121) boundary layers. Trends observed in the model are supported by wall-modelled large-eddy simulation of the zero-pressure-gradient case for Re_x in the range 10^8\u221210^(10) and for four values of \u03b1. Linear streamwise growth of the displacement, momentum and nominal boundary-layer thicknesses is confirmed, while, for each \u03b1, the mean-velocity profiles and streamwise turbulent variances are found to collapse reasonably well onto z/(\u03b1x)z. For given \u03b1, calculations of U^+_\u221e obtained from large-eddy simulations are streamwise constant and independent of Re_x when this is large. The present results suggest that, in the sense that U^+_\u221e(\u03b1,m) is constant, these flows can be interpreted as the fully rough limit for boundary layers in the presence of small-scale linear roughness.", "date": "2017-05", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "818", "publisher": "Cambridge University Press", "pagerange": "26-45", "id_number": "CaltechAUTHORS:20170428-133814936", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170428-133814936", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "King Abdullah University of Science and Technology (KAUST)", "grant_number": "URF/1/1394-01" }, { "agency": "NSF", "grant_number": "CBET-1235605" }, { "agency": "King Abdullah University of Science and Technology (KAUST)", "grant_number": "URF/1/1394-01" } ] }, "doi": "10.1017/jfm.2017.132", "resource_type": "article", "pub_year": "2017", "author_list": "Sridhar, A.; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/ntzad-d9a96", "eprint_id": 73472, "eprint_status": "archive", "datestamp": "2023-08-19 00:48:19", "lastmod": "2023-10-24 15:23:10", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Mostert-W", "name": { "family": "Mostert", "given": "W." }, "orcid": "0000-0001-6251-4136" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Samtaney-Ravi", "name": { "family": "Samtaney", "given": "R." }, "orcid": "0000-0002-4702-6473" }, { "id": "Wheatley-V", "name": { "family": "Wheatley", "given": "V." } } ] }, "title": "Geometrical shock dynamics for magnetohydrodynamic fast shocks", "ispublished": "pub", "full_text_status": "restricted", "keywords": "compressible flows, shock waves, MHD and electrohydrodynamics", "note": "\u00a9 2016 Cambridge University Press. \n\nReceived 2 September 2016; revised 25 October 2016; accepted 10 November 2016; first published online 12 December 2016. \n\nThis research was supported by the KAUST Office of Sponsored Research under award URF/1/2162-01. V.W. holds an Australian Research Council Discovery Early Career Researcher Award (project number DE120102942).", "abstract": "We describe a formulation of two-dimensional geometrical shock dynamics (GSD) suitable for ideal magnetohydrodynamic (MHD) fast shocks under magnetic fields of general strength and orientation. The resulting area\u2013Mach-number\u2013shock-angle relation is then incorporated into a numerical method using pseudospectral differentiation. The MHD-GSD model is verified by comparison with results from nonlinear finite-volume solution of the complete ideal MHD equations applied to a shock implosion flow in the presence of an oblique and spatially varying magnetic field ahead of the shock. Results from application of the MHD-GSD equations to the stability of fast MHD shocks in two dimensions are presented. It is shown that the time to formation of triple points for both perturbed MHD and gas-dynamic shocks increases as \u03f5^(-1), where \u03f5 is a measure of the initial Mach-number perturbation. Symmetry breaking in the MHD case is demonstrated. In cylindrical converging geometry, in the presence of an azimuthal field produced by a line current, the MHD shock behaves in the mean as in Pullin et al. (Phys. Fluids, vol. 26, 2014, 097103), but suffers a greater relative pressure fluctuation along the shock than the gas-dynamic shock.", "date": "2017-01", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "811", "publisher": "Cambridge University Press", "pagerange": "Art. No. R2", "id_number": "CaltechAUTHORS:20170112-111948222", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170112-111948222", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "King Abdullah University of Science and Technology (KAUST)", "grant_number": "URF/1/2162-01" }, { "agency": "Australian Research Council", "grant_number": "DE120102942" } ] }, "doi": "10.1017/jfm.2016.767", "resource_type": "article", "pub_year": "2017", "author_list": "Mostert, W.; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/zvpnj-p2f29", "eprint_id": 73755, "eprint_status": "archive", "datestamp": "2023-08-19 00:48:43", "lastmod": "2023-10-24 16:25:19", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Mostert-W", "name": { "family": "Mostert", "given": "W." }, "orcid": "0000-0001-6251-4136" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Wheatley-V", "name": { "family": "Wheatley", "given": "V." } }, { "id": "Samtaney-Ravi", "name": { "family": "Samtaney", "given": "R." }, "orcid": "0000-0002-4702-6473" } ] }, "title": "Magnetohydrodynamic implosion symmetry and suppression of Richtmyer-Meshkov instability in an octahedrally symmetric field", "ispublished": "pub", "full_text_status": "public", "note": "\u00a9 2017 American Physical Society. \n\nReceived 18 May 2016; published 26 January 2017. \n\nThis research was supported by the KAUST Office of Sponsored Research under Award No. URF/1/2162-01. V.W. acknowledges support from an Australian Research Council Discovery Early Career Researcher Award (Project No. DE120102942).\n\nPublished - PhysRevFluids.2.013701.pdf
", "abstract": "We present numerical simulations of ideal magnetohydrodynamics showing suppression of the Richtmyer-Meshkov instability in spherical implosions in the presence of an octahedrally symmetric magnetic field. This field configuration is of interest owing to its high degree of spherical symmetry in comparison with previously considered dihedrally symmetric fields. The simulations indicate that the octahedral field suppresses the instability comparably to the other previously considered candidate fields for light-heavy interface accelerations while retaining a highly symmetric underlying flow even at high field strengths. With this field, there is a reduction in the root-mean-square perturbation amplitude of up to approximately 50% at representative time under the strongest field tested while maintaining a homogeneous suppression pattern compared to the other candidate fields.", "date": "2017-01", "date_type": "published", "publication": "Physical Review Fluids", "volume": "2", "number": "1", "publisher": "American Physical Society", "pagerange": "Art. No. 013701", "id_number": "CaltechAUTHORS:20170126-111428510", "issn": "2469-990X", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170126-111428510", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "King Abdullah University of Science and Technology (KAUST)", "grant_number": "URF/1/2162-01" }, { "agency": "Australian Research Council", "grant_number": "DE120102942" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1103/PhysRevFluids.2.013701", "primary_object": { "basename": "PhysRevFluids.2.013701.pdf", "url": "https://authors.library.caltech.edu/records/zvpnj-p2f29/files/PhysRevFluids.2.013701.pdf" }, "resource_type": "article", "pub_year": "2017", "author_list": "Mostert, W.; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/kteg5-nbg16", "eprint_id": 66421, "eprint_status": "archive", "datestamp": "2023-08-20 11:04:17", "lastmod": "2023-10-18 18:04:03", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Mostert-W", "name": { "family": "Mostert", "given": "W." }, "orcid": "0000-0001-6251-4136" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Samtaney-Ravi", "name": { "family": "Samtaney", "given": "R." }, "orcid": "0000-0002-4702-6473" }, { "id": "Wheatley-V", "name": { "family": "Wheatley", "given": "V." } } ] }, "title": "Converging cylindrical magnetohydrodynamic shock collapse onto a power-law-varying line current", "ispublished": "pub", "full_text_status": "restricted", "keywords": "compressible flows, MHD and electrohydrodynamics, shock waves", "note": "\u00a9 2016 Cambridge University Press. \n\nReceived 15 June 2015; revised 8 December 2015; accepted 14 February 2016; first published online 16 March 2016. \n\nThis research was supported under Australian Research Council's Discovery Projects funding scheme (project number DP120102378). W. Mostert is supported by an Australian Postgraduate Award and was the recipient of a Graduate School International Travel Award from the University of Queensland. In addition, V. Wheatley is the recipient of an Australian Research Council Discovery Early Career Researcher Award (project number DE120102942). This work was partially supported by the KAUST Office of Sponsored Research under award URF/1/2162-01.", "abstract": "We investigate the convergence behaviour of a cylindrical, fast magnetohydrodynamic (MHD) shock wave in a neutrally ionized gas collapsing onto an axial line current that generates a power law in time, azimuthal magnetic field. The analysis is done within the framework of a modified version of ideal MHD for an inviscid, non-dissipative, neutrally ionized compressible gas. The time variation of the magnetic field is tuned such that it approaches zero at the instant that the shock reaches the axis. This configuration is motivated by the desire to produce a finite magnetic field at finite shock radius but a singular gas pressure and temperature at the instant of shock impact. Our main focus is on the variation with shock radius r, as r\u21920, of the shock Mach number M(r) and pressure behind the shock p(r) as a function of the magnetic field power-law exponent \u03bc \u2a7e 0, where \u03bc = 0 gives a constant-in-time line current. The flow problem is first formulated using an extension of geometrical shock dynamics (GSD) into the time domain to take account of the time-varying conditions ahead of the converging shock, coupled with appropriate shock-jump conditions for a fast, symmetric MHD shock. This provides a pair of ordinary differential equations describing both M(r) and the time evolution on the shock, as a function of r, constrained by a collapse condition required to achieve tuned shock convergence. Asymptotic, analytical results for M(r) and p(r) are obtained over a range of \u03bc for general \u03b3, and for both small and large r. In addition, numerical solutions of the GSD equations are performed over a large range of r, for selected parameters using \u03b3=5/3. The accuracy of the GSD model is verified for some cases using direct numerical solution of the full, radially symmetric MHD equations using a shock-capturing method. For the GSD solutions, it is found that the physical character of the shock convergence to the axis is a strong function of \u03bc. For 0 \u2a7d \u03bc < 4/13, M and p both approach unity at shock impact r=0 owing to the dominance of the strong magnetic field over the amplifying effects of geometrical convergence. When \u03bc\u2a7e0.816 (for \u03b3=5/3), geometrical convergence is dominant and the shock behaves similarly to a converging gas dynamic shock with singular M(r) and p(r), r\u21920. For 4/13 < \u03bc \u2a7d 0.816 three distinct regions of M(r) variation are identified. For each of these p(r) is singular at the axis.", "date": "2016-04", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "793", "publisher": "Cambridge University Press", "pagerange": "414-443", "id_number": "CaltechAUTHORS:20160422-142035961", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160422-142035961", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Australian Research Council", "grant_number": "DP120102378" }, { "agency": "University of Queensland" }, { "agency": "Australian Research Council", "grant_number": "DE120102942" }, { "agency": "King Abdullah University of Science and Technology (KAUST)", "grant_number": "URF/1/2162-01" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/jfm.2016.138", "resource_type": "article", "pub_year": "2016", "author_list": "Mostert, W.; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/rdm1f-15s89", "eprint_id": 63384, "eprint_status": "archive", "datestamp": "2023-08-22 16:56:19", "lastmod": "2023-10-25 23:46:51", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Cheng-Wan", "name": { "family": "Cheng", "given": "W." }, "orcid": "0000-0003-3960-4162" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Samtaney-Ravi", "name": { "family": "Samtaney", "given": "R." }, "orcid": "0000-0002-4702-6473" } ] }, "title": "Large-eddy simulation of separation and reattachment of a flat plate turbulent boundary layer", "ispublished": "pub", "full_text_status": "public", "keywords": "turbulence modelling; turbulent boundary layers; turbulent flows", "note": "\u00a9 2015 Cambridge University Press. \n\nReceived 16 March 2015; revised 19 August 2015; accepted 15 October 2015; first published online 11 November 2015. \n\nW.C. and R.S. were supported by the KAUST Office of Competitive Research Funds (OCRF) under Award No. URF/1/1394-01. D.I.P. was partially supported under KAUST OCRF Award No. URF/1/1394-01 and partially by NSF award CBET 1235605.\n\nPublished - S0022112015006047a.pdf
", "abstract": "We present large-eddy simulations (LES) of separation and reattachment of a flat-plate turbulent boundary-layer flow. Instead of resolving the near wall region, we develop a two-dimensional virtual wall model which can calculate the time- and space-dependent skin-friction vector field at the wall, at the resolved scale. By combining the virtual-wall model with the stretched-vortex subgrid-scale (SGS) model, we construct a self-consistent framework for the LES of separating and reattaching turbulent wall-bounded flows at large Reynolds numbers. The present LES methodology is applied to two different experimental flows designed to produce separation/reattachment of a flat-plate turbulent boundary layer at medium Reynolds number Re_\u03b8 based on the momentum boundary-layer thickness \u03b8. Comparison with data from the first case at Re_\u03b8=2000 demonstrates the present capability for accurate calculation of the variation, with the streamwise co-ordinate up to separation, of the skin friction coefficient, Re_\u03b8, the boundary-layer shape factor and a non-dimensional pressure-gradient parameter. Additionally the main large-scale features of the separation bubble, including the mean streamwise velocity profiles, show good agreement with experiment. At the larger Re_\u03b8=11000 of the second case, the LES provides good postdiction of the measured skin-friction variation along the whole streamwise extent of the experiment, consisting of a very strong adverse pressure gradient leading to separation within the separation bubble itself, and in the recovering or reattachment region of strongly-favourable pressure gradient. Overall, the present two-dimensional wall model used in LES appears to be capable of capturing the quantitative features of a separation-reattachment turbulent boundary-layer flow at low to moderately large Reynolds numbers.", "date": "2015-12", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "785", "publisher": "Cambridge University Press", "pagerange": "78-108", "id_number": "CaltechAUTHORS:20160105-124250245", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160105-124250245", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "King Abdullah University of Science and Technology (KAUST)", "grant_number": "URF/1/1394-01" }, { "agency": "NSF", "grant_number": "CBET-1235605" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/jfm.2015.604", "primary_object": { "basename": "S0022112015006047a.pdf", "url": "https://authors.library.caltech.edu/records/rdm1f-15s89/files/S0022112015006047a.pdf" }, "resource_type": "article", "pub_year": "2015", "author_list": "Cheng, W.; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/rpzmb-hd368", "eprint_id": 62607, "eprint_status": "archive", "datestamp": "2023-08-20 08:34:54", "lastmod": "2023-10-25 17:16:31", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Mostert-W", "name": { "family": "Mostert", "given": "W." }, "orcid": "0000-0001-6251-4136" }, { "id": "Wheatley-V", "name": { "family": "Wheatley", "given": "V." } }, { "id": "Samtaney-Ravi", "name": { "family": "Samtaney", "given": "R." }, "orcid": "0000-0002-4702-6473" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Effects of magnetic fields on magnetohydrodynamic cylindrical and spherical Richtmyer-Meshkov instability", "ispublished": "pub", "full_text_status": "public", "note": "\u00a9 2015 AIP Publishing LLC. \n\nReceived 29 June 2015; accepted 17 September 2015; published online 6 October 2015. \n\nThis research was partially supported under Australian Research Council's Discovery Projects funding scheme (Project No. DP120102378). W. Mostert is supported by an Australian Postgraduate Award. Dr Wheatley is the recipient of an Australian Research Council Discovery Early Career Researcher Award (Project No. DE120102942). This work was partially supported by the KAUST Office of Sponsored Research under Award URF/1/2162-01.\n\nPublished - 1.4932110.pdf
", "abstract": "The effects of seed magnetic fields on the Richtmyer-Meshkov instability driven by converging cylindrical and spherical implosions in ideal magnetohydrodynamics are investigated. Two different seed field configurations at various strengths are applied over a cylindrical or spherical density interface which has a single-dominant-mode perturbation. The shocks that excite the instability are generated with appropriate Riemann problems in a numerical formulation and the effect of the seed field on the growth rate and symmetry of the perturbations on the density interface is examined. We find reduced perturbation growth for both field configurations and all tested strengths. The extent of growth suppression increases with seed field strength but varies with the angle of the field to interface. The seed field configuration does not significantly affect extent of suppression of the instability, allowing it to be chosen to minimize its effect on implosion distortion. However, stronger seed fields are required in three dimensions to suppress the instability effectively.", "date": "2015-10-06", "date_type": "published", "publication": "Physics of Fluids", "volume": "27", "number": "10", "publisher": "American Institute of Physics", "pagerange": "Art. No. 104102", "id_number": "CaltechAUTHORS:20151204-094841119", "issn": "1070-6631", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151204-094841119", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Australian Research Council", "grant_number": "DP120102378" }, { "agency": "Australian Postgraduate Award" }, { "agency": "Australian Research Council", "grant_number": "DE120102942" }, { "agency": "King Abdullah University of Science and Technology (KAUST)", "grant_number": "URF/1/2162-01" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.4932110", "primary_object": { "basename": "1.4932110.pdf", "url": "https://authors.library.caltech.edu/records/rpzmb-hd368/files/1.4932110.pdf" }, "resource_type": "article", "pub_year": "2015", "author_list": "Mostert, W.; Wheatley, V.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/0cnpy-6kf38", "eprint_id": 56348, "eprint_status": "archive", "datestamp": "2023-08-22 15:03:02", "lastmod": "2023-10-23 15:20:17", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "L\u00f3pez-Ortega-A", "name": { "family": "L\u00f3pez-Ortega", "given": "A." } }, { "id": "Lombardini-Manuel", "name": { "family": "Lombardini", "given": "M." } }, { "id": "Barton-Philip-T", "name": { "family": "Barton", "given": "P. T." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Meiron-D-I", "name": { "family": "Meiron", "given": "D. I." }, "orcid": "0000-0003-0397-3775" } ] }, "title": "Richtmyer-Meshkov instability for elastic-plastic solids in converging geometries", "ispublished": "pub", "full_text_status": "restricted", "keywords": "Richmyer\u2013Meshkov instability; Eulerian algorithm; Hyper-elastic constitutive laws; Shocks in solids", "note": "\u00a9 2014 Elsevier Ltd.\n\nReceived 18 June 2014; Accepted 6 December 2014; Available online 12 December 2014.\n\nThis work was supported by the Department of Energy National Nuclear Security Administration under Award no. DE-FC52-08NA28613.", "abstract": "We present a detailed study of the interface instability that develops at the boundary between a shell of elastic\u2013plastic material and a cylindrical core of confined gas during the inbound implosive motion generated by a shock-wave. The main instability in this configuration is the so-called Richtmyer\u2013Meshkov instability that arises when the shock wave crosses the material interface. Secondary instabilities, such as Rayleigh\u2013Taylor, due to the acceleration of the interface, and Kelvin\u2013Helmholtz, due to slip between solid and fluid, arise as the motion progresses. The reflection of the shock wave at the axis and its second interaction with the material interface as the shock moves outbound, commonly known as re-shock, results in a second Richtmyer\u2013Meshkov instability that potentially increases the growth rate of interface perturbations, resulting in the formation of a mixing zone typical of fluid\u2013fluid configurations and the loss of the initial perturbation length scales. The study of this problem is of interest for achieving stable inertial confinement fusion reactions but its complexity and the material conditions produced by the implosion close to the axis prove to be challenging for both experimental and numerical approaches. In this paper, we attempt to circumvent some of the difficulties associated with a classical numerical treatment of this problem, such as element inversion in Lagrangian methods or failure to maintain the relationship between the determinant of the deformation tensor and the density in Eulerian approaches, and to provide a description of the different events that occur during the motion of the interface. For this purpose, a multi-material numerical solver for evolving in time the equations of motion for solid and fluid media in an Eulerian formalism has been implemented in a Cartesian grid. Equations of state are derived using thermodynamically consistent hyperelastic relations between internal energy and stresses. The resolution required for capturing the state of solid and fluid materials close to the origin is achieved by making use of adaptive mesh refinement techniques. Rigid-body rotations contained in the deformation tensor have been shown to have a negative effect on the accuracy of the method in extreme compression conditions and are removed by transforming the deformation tensor into a stretch tensor at each time step. With this methodology, the evolution of the interface can be tracked up to a point at which numerical convergence cannot be achieved due to the inception of numerical Kelvin\u2013Helmholtz instabilities caused by slip between materials. From that point, only qualitative conclusions can be extracted from this analysis. The influence of different geometrical parameters, initial conditions, and material properties on the motion of the interface are investigated. Some major differences are found with respect to the better understood fluid\u2013fluid case. For example, increasing the wave number of the interface perturbations leads to a second phase reversal of the interface (i.e., the first phase reversal of the interface naturally occurs due to the initial negative growth-rate of the instability as the shock wave transitions from the high-density material to the low-density one). This phenomenon is caused by the compressive effect of the converging geometry and the low density of the gas with respect to the solid, which allows for the formation of an incipient spike in the center of an already existing bubble. Multiple solid\u2013gas density ratios are also considered. Results show that the motion of the interface asymptotically converges to the solid\u2013vacuum case. When a higher initial density for the gas is considered, the growth rate of interface perturbations decreases and, in some situations, its sign may reverse, as the fluid becomes more dense than the solid due to having higher compressibility. Finally, the influence of the Mach number of the driving shock and the yield stress on the mixing-zone is examined. We find that the width of the mixing zone produced after the re-shock increases in proportion to the strength of the incident shock. An increased yield stress in the solid material makes the interface less unstable due to vorticity being carried away from the interface by shear waves and limits the generation of smaller length scales after the re-shock.", "date": "2015-03", "date_type": "published", "publication": "Journal of the Mechanics and Physics of Solids", "volume": "76", "publisher": "Elsevier", "pagerange": "291-324", "id_number": "CaltechAUTHORS:20150403-130428593", "issn": "0022-5096", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150403-130428593", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Department of Energy (DOE) National Nuclear Security Administration", "grant_number": "DE-FC52-08NA28613" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1016/j.jmps.2014.12.002", "resource_type": "article", "pub_year": "2015", "author_list": "L\u00f3pez-Ortega, A.; Lombardini, M.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/8sfcn-79y08", "eprint_id": 55952, "eprint_status": "archive", "datestamp": "2023-08-20 04:25:17", "lastmod": "2023-10-20 23:28:22", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Mihaly-J-M", "name": { "family": "Mihaly", "given": "Jonathan M." } }, { "id": "Tandy-J-D", "name": { "family": "Tandy", "given": "Jonathan D." } }, { "id": "Rosakis-A-J", "name": { "family": "Rosakis", "given": "A. J." }, "orcid": "0000-0003-0559-0794" }, { "id": "Adams-M-A", "name": { "family": "Adams", "given": "M. A." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D." } } ] }, "title": "Pressure-Dependent, Infrared-Emitting Phenomenon in Hypervelocity Impact", "ispublished": "pub", "full_text_status": "public", "note": "\u00a9 2015 by ASME.\n\nContributed by the Applied Mechanics Division of ASME for publication in the\nJournal of Applied Mechanics. Manuscript received June 2, 2014; final manuscript received October 17, 2014; accepted manuscript posted October 21, 2014; published online November 19, 2014.\n\nThis material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award No. DE-FC52-08NA28613. The authors would also like to thank Michael Mello for his assistance with the optomechanical design of the LSL system and Petros Arakelian for his assistance in installing the optical benches and safety\nfeature.\n\nPublished - jam_082_01_011004.pdf
", "abstract": "A series of hypervelocity impact experiments were conducted with variable target chamber atmospheric pressure ranging from 0.9 to 21.5\u2009Torr. Using a two-stage light-gas gun, 5.7\u2009mg nylon 6/6 right-cylinders were accelerated to speeds ranging between 6.0 and 6.3\u2009km/s to impact 1.5\u2009mm thick 6061-T6 aluminum plates. Full-field images of near-IR emission (0.9 to 1.7\u2009\u03bcm) were measured using a high-speed spectrograph system with image exposure times of 1\u2009\u03bcs. The radial expansion of an IR-emitting impact-generated phenomenon was observed to be dependent upon the ambient target chamber atmospheric pressures. Higher chamber pressures demonstrated lower radial expansions of the subsequently measured IR-emitting region uprange of the target. Dimensional analysis, originally presented by Taylor to describe the expansion of a hemispherical blast wave, is applied to describe the observed pressure-dependence of the IR-emitting cloud expansion. Experimental results are used to empirically determine two dimensionless constants for the analysis. The maximum radial expansion of the observed IR-emitting cloud is described by the Taylor blast-wave theory, with experimental results demonstrating the characteristic nonlinear dependence on atmospheric pressure. Furthermore, the edges of the measured IR-emitting clouds are observed to expand at extreme speeds ranging from approximately 13 to 39\u2009km/s. In each experiment, impact ejecta and debris are simultaneously observed in the visible range using an ultrahigh-speed laser shadowgraph system. For the considered experiments, ejecta and debris speeds are measured between 0.6 and 5.1\u2009km/s. Such a disparity in observed phenomena velocities suggests the IR-emitting cloud is a distinctly different phenomenon to both the uprange ejecta and downrange debris generated during a hypervelocity impact.", "date": "2015-01", "date_type": "published", "publication": "Journal of Applied Mechanics", "volume": "82", "number": "1", "publisher": "American Society Mechanical Engineers", "pagerange": "Art. No. 011004", "id_number": "CaltechAUTHORS:20150320-155256012", "issn": "0021-8936", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150320-155256012", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Department of Energy (DOE) National Nuclear Security Administration", "grant_number": "DE-FC52-08NA28613" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1115/1.4028856", "primary_object": { "basename": "jam_082_01_011004.pdf", "url": "https://authors.library.caltech.edu/records/8sfcn-79y08/files/jam_082_01_011004.pdf" }, "resource_type": "article", "pub_year": "2015", "author_list": "Mihaly, Jonathan M.; Tandy, Jonathan D.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/vpz67-rb434", "eprint_id": 78430, "eprint_status": "archive", "datestamp": "2023-08-20 04:17:59", "lastmod": "2023-10-26 00:05:36", "type": "book_section", "metadata_visibility": "show", "creators": { "items": [ { "id": "L\u00f3pez-Ortega-A", "name": { "family": "L\u00f3pez-Ortega", "given": "A." } }, { "id": "Lombardini-Manuel", "name": { "family": "Lombardini", "given": "M." } }, { "id": "Barton-Philip-T", "name": { "family": "Barton", "given": "P. T." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Meiron-D-I", "name": { "family": "Meiron", "given": "D. I." }, "orcid": "0000-0003-0397-3775" } ] }, "title": "Richtmyer-Meshkov Instability at Solid-Gas Interfaces", "ispublished": "unpub", "full_text_status": "restricted", "note": "\u00a9 2015 Springer International Publishing Switzerland. \n\nThis work was partially supported by the Department of Energy National Nuclear Security Administration under Award Number DE-FC52-08NA28613.", "abstract": "The impact of a shock-wave onto a perturbed interface separating materials of different density and initially at rest in a laboratory frame of reference is described as a Richtmer-Meshkov (RM) flow, following Richtmyer [1], who obtained a numerical solution to the linearized equations for perfect fluids using an impulsive model, and Meshkov [2], who performed shock-tube experiments for gaseous materials.", "date": "2015", "date_type": "published", "publisher": "Springer", "place_of_pub": "Cham, Switzerland", "pagerange": "1131-1136", "id_number": "CaltechAUTHORS:20170621-144124277", "isbn": "978-3-319-16837-1", "book_title": "29th International Symposium on Shock Waves", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170621-144124277", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Department of Energy (DOE) National Nuclear Security Administration", "grant_number": "DE-FC52-08NA28613" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "contributors": { "items": [ { "id": "Bonazza-Ricardo", "name": { "family": "Bonazza", "given": "Ricardo" } }, { "id": "Devesh-Ricardo", "name": { "family": "Devesh", "given": "Ricardo" } } ] }, "doi": "10.1007/978-3-319-16838-8_54", "resource_type": "book_section", "pub_year": "2015", "author_list": "L\u00f3pez-Ortega, A.; Lombardini, M.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/73dzg-dw084", "eprint_id": 54240, "eprint_status": "archive", "datestamp": "2023-08-20 03:50:25", "lastmod": "2023-10-20 15:43:16", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Mostert-W", "name": { "family": "Mostert", "given": "W." }, "orcid": "0000-0001-6251-4136" }, { "id": "Wheatley-V", "name": { "family": "Wheatley", "given": "V." } }, { "id": "Samtaney-Ravi", "name": { "family": "Samtaney", "given": "R." }, "orcid": "0000-0002-4702-6473" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Effects of seed magnetic fields on magnetohydrodynamic implosion structure and dynamics", "ispublished": "pub", "full_text_status": "public", "note": "\u00a9 2014 AIP Publishing LLC.\n\nReceived 25 July 2014; accepted 12 November 2014; published online 8 December 2014.\n\nThis research was supported under Australian Research Councils Discovery Projects funding scheme (Project No. DP120102378). W. Mostert is supported by an Australian Post-graduate Award. Dr Wheatley is the recipient of an Australian Research Council Discovery Early Career\nResearcher Award (Project No. DE120102942). Professor Samtaney is partially supported by a KAUST Base Research Award. We would also like to thank Myall Hingee for his useful contribution to the research.\n\nPublished - 1.4902432.pdf
", "abstract": "The effects of various seed magnetic fields on the dynamics of cylindrical and spherical implosions in ideal magnetohydrodynamics are investigated. Here, we present a fundamental investigation of this problem utilizing cylindrical and spherical Riemann problems under three seed field configurations to initialize the implosions. The resulting flows are simulated numerically, revealing rich flow structures, including multiple families of magnetohydrodynamic shocks and rarefactions that interact non-linearly. We fully characterize these flow structures, examine their axi- and spherisymmetry-breaking behaviour, and provide data on asymmetry evolution for different field strengths and driving pressures for each seed field configuration. We find that out of the configurations investigated, a seed field for which the implosion centre is a saddle point in at least one plane exhibits the least degree of asymmetry during implosion.", "date": "2014-12", "date_type": "published", "publication": "Physics of Fluids", "volume": "26", "number": "12", "publisher": "American Institute of Physics", "pagerange": "Art. No. 126102", "id_number": "CaltechAUTHORS:20150130-091306770", "issn": "1070-6631", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150130-091306770", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Australian Research Council", "grant_number": "DP120102378" }, { "agency": "Australian Post-graduate Award" }, { "agency": "Australian Research Council", "grant_number": "DE120102942" }, { "agency": "King Abdullah University of Science and Technology (KAUST)" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.4902432", "primary_object": { "basename": "1.4902432.pdf", "url": "https://authors.library.caltech.edu/records/73dzg-dw084/files/1.4902432.pdf" }, "resource_type": "article", "pub_year": "2014", "author_list": "Mostert, W.; Wheatley, V.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/9szaz-3js27", "eprint_id": 53466, "eprint_status": "archive", "datestamp": "2023-08-20 03:48:58", "lastmod": "2023-10-19 21:46:38", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Yang-Yue", "name": { "family": "Yang", "given": "Yue" } } ] }, "title": "Whither vortex tubes?", "ispublished": "pub", "full_text_status": "restricted", "note": "\u00a9 2014 The Japan Society of Fluid Mechanics and IOP Publishing Ltd. Received 9 July 2014, revised 20 September 2014. Accepted for publication 23 May 2014. Published 6 November 2014. Communicated by Y Hattori. \n\nIUTAM Symposium on Vortex Dynamics - Formation, Structure and Function, Kyushu Univ Sch Med, Fukuoka, JAPAN, MAR 10-14, 2013.\n\nThis work has been supported in part by the National Science Foundation under grant DMS-1016111.", "abstract": "We review research aimed at the development of an analytical and numerical framework for tracking the evolution, in an incompressible viscous fluid, of scalar fields, called `vortex surface fields' (VSFs), whose instantaneous isosurfaces always contain continuous vortex lines. A set of equations describing the evolution of VSFs starting from a known initial condition is proposed and discussed. Non-uniqueness in the initial-value problem is resolved with the introduction of evolution in a pseudo-time variable where the vorticity, frozen in real time, plays the role of an advecting field. A numerical method for following both the real and pseudo-time evolution is described and its regularization properties are discussed. Examples are given of following VSFs in a viscous Taylor-Green flow (Taylor and Green 1937 Proc. R. Soc. A 158 499-521). The prospects for extending these ideas to fully turbulent flows are discussed.", "date": "2014-12", "date_type": "published", "publication": "Fluid Dynamics Research", "volume": "46", "number": "6", "publisher": "IOP", "pagerange": "Art. No. 061418", "id_number": "CaltechAUTHORS:20150109-105826366", "issn": "0169-5983", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150109-105826366", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF", "grant_number": "DMS-1016111" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1088/0169-5983/46/6/061418", "resource_type": "article", "pub_year": "2014", "author_list": "Pullin, D. I. and Yang, Yue" }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/75kbq-bze72", "eprint_id": 51575, "eprint_status": "archive", "datestamp": "2023-08-19 00:14:13", "lastmod": "2023-10-18 16:51:45", "type": "monograph", "metadata_visibility": "show", "creators": { "items": [ { "id": "Candler-G-V", "name": { "family": "Candler", "given": "G. V." } }, { "id": "Dimotakis-P-E", "name": { "family": "Dimotakis", "given": "P. E." } }, { "id": "Hornung-H-G", "name": { "family": "Hornung", "given": "H. G." }, "orcid": "0000-0002-4903-8419" }, { "id": "Leonard-A", "name": { "family": "Leonard", "given": "A." } }, { "id": "Meiron-D-I", "name": { "family": "Meiron", "given": "D. I." }, "orcid": "0000-0003-0397-3775" }, { "id": "McKoy-V", "name": { "family": "McKoy", "given": "B. V." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Sturtevant-B", "name": { "family": "Sturtevant", "given": "B." } } ] }, "title": "Interaction of Chemistry, Turbulence, and Shock Waves in Hypervelocity Flow", "ispublished": "unpub", "full_text_status": "public", "note": "\u00a9 1996 California Institute of Technology.\n\nAnnual Progress Report Prepared for Air Force Office of Scientific Research.\n\nAFOSR URI GRANT G - F49620-93-1-0338.\n\nSubmitted - FM96-7.pdf
", "abstract": "Significant progress was made in the third year of an interdisciplinary experimental, numerical and theoretical program to extend the state of knowledge\nand understanding of the effects of chemical reactions in hypervelocity flows. The program addressed the key problems in aerothermochemistry that arise from.the interaction between the three strongly nonlinear effects:\nCompressibility; vorticity; and chemistry. Important new results included:\n\u2022 New data on transition in hypervelocity carbon dioxide flows\n\u2022 New method of free-piston shock tunnel operation for lower enthalpy\n\u2022 Accurate new method for computation of self-similar flows\n\u2022 New experimental data on flap-induced separation at high enthalpy\n\u2022 Insight into mechanisms active in reacting shear layers from comparison of experiment and computation\n\u2022 Extensive new data from Rayleigh scattering diagnostics of supersonic shear layer\n\u2022 Comparison of new experiments and computation of hypervelocity double-wedge flow yielded important differences \n\u2022 Further first-principles computations of electron collision cross-sections of CO, N_2 and NO\n\u2022 Good agreement between EFMO computation and experiment of flow over a cone at high incidence\n\u2022 Extension of LITA diagnostics to high temperature.", "date": "2014-11-11", "date_type": "published", "publisher": "California Institute of Technology", "id_number": "CaltechAUTHORS:20141111-111211793", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141111-111211793", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Air Force Office of Scientific Research (AFOSR)", "grant_number": "F49620-93-1-0338" } ] }, "other_numbering_system": { "items": [ { "id": "96-7", "name": "GALCIT FM" } ] }, "local_group": { "items": [ { "id": "Graduate-Aeronautical-Laboratories-(Fluid-Mechanics)" }, { "id": "GALCIT" } ] }, "doi": "10.7907/wbg4-ra84", "primary_object": { "basename": "FM96-7.pdf", "url": "https://authors.library.caltech.edu/records/75kbq-bze72/files/FM96-7.pdf" }, "resource_type": "monograph", "pub_year": "2014", "author_list": "Candler, G. V.; Dimotakis, P. E.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/saw0s-se228", "eprint_id": 50784, "eprint_status": "archive", "datestamp": "2023-08-22 14:02:10", "lastmod": "2023-10-18 14:30:44", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Saito-N", "name": { "family": "Saito", "given": "Namiko" } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Large eddy simulation of smooth\u2013rough\u2013smooth transitions in turbulent channel flows", "ispublished": "pub", "full_text_status": "restricted", "keywords": "Turbulent; High Reynolds number; LES; Roughness; Wall model", "note": "\u00a9 2014 Elsevier Ltd.\n\nReceived 12 December 2013; Received in revised form 28 June 2014; Accepted 29 June 2014; Available online 6 August 2014.\n\nThis work has been supported in part by the National Science\nFoundation under Grant CBET-1235605. Helpful discussions with\nBeverley McKeon are gratefully acknowledged.", "abstract": "We describe a high Reynolds number large-eddy-simulation (LES) study of turbulent flow in a long channel of length 128 channel half heights, \u03b4, with the walls consisting of roughness strips where the long stream-wise extent invites a full relaxation of the mean velocities within each strip. The channel is stream-wise periodic and strips are oriented transverse to the flow resulting in repeated transitions between smooth and rough surfaces along the stream-wise direction. The present LES uses a wall model that contains Colebrook's empirical formula as a roughness correction to both the local and dynamic calculation of the friction velocity and also the LES wall boundary condition. This operates point-wise across wall surfaces, and hence changes in the outer flow can be viewed as a response to the temporally and/or spatially variant roughness distribution. At the wall surface, dynamically calculated levels of time- and span-wise-averaged friction velocity u_\u03c4[bar](x) over/undershoot and then fully recover towards their smooth or rough state over a stream-wise distance of order 10\u201330 \u03b4\u03b4 depending on both roughness and Reynolds number. Also, the initial response rate in u_\u03c4[bar] shows Reynolds number and roughness dependence over both transitions. The growth rate of the internal boundary layer (IBL), defined by the abrupt change in stream-wise turbulent intensity, is found to grow as x^0.70 on average over multiple simulation conditions for the case of a smooth-to-rough transition, which agrees with the experimental results of Antonia and Luxton (1971) [1] and Efros and Krogstad (2011) [2]. IBL profiles demonstrate a good collapse on \u03b4/log(Re^(*)_(\u03c4)), where View the Re^(*)_(\u03c4) is the local Reynolds number based on u_\u03c4[bar] at the point of full recovery.", "date": "2014-11", "date_type": "published", "publication": "International Journal of Heat and Mass Transfer", "volume": "78", "publisher": "Elsevier", "pagerange": "707-720", "id_number": "CaltechAUTHORS:20141024-110858324", "issn": "0017-9310", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141024-110858324", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF", "grant_number": "CBET-1235605" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1016/j.ijheatmasstransfer.2014.06.088", "resource_type": "article", "pub_year": "2014", "author_list": "Saito, Namiko and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/9g5bw-rnz75", "eprint_id": 50089, "eprint_status": "archive", "datestamp": "2023-08-20 02:43:51", "lastmod": "2023-10-17 22:30:18", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Mostert-W", "name": { "family": "Mostert", "given": "W." }, "orcid": "0000-0001-6251-4136" }, { "id": "Wheatley-V", "name": { "family": "Wheatley", "given": "V." } }, { "id": "Samtaney-Ravi", "name": { "family": "Samtaney", "given": "R." }, "orcid": "0000-0002-4702-6473" } ] }, "title": "Converging cylindrical shocks in ideal magnetohydrodynamics", "ispublished": "pub", "full_text_status": "public", "note": "\u00a9 2014 AIP Publishing LLC. Received 9 May 2014; accepted 22 August 2014; published online 16 September 2014.\n\nThis research was supported under Australian Research Council's Discovery Projects funding scheme (Project No. DP120102378). Additionally, V. Wheatley is the recipient of an Australian Research Council Discovery Early Career Researcher Award (Project No. DE120102942). R. Samtaney\nwas supported by baseline research funds at KAUST.\n\nPublished - 1.4894743.pdf
", "abstract": "We consider a cylindrically symmetrical shock converging onto an axis within the framework of ideal, compressible-gas non-dissipative magnetohydrodynamics (MHD). In cylindrical polar co-ordinates we restrict attention to either constant axial magnetic field or to the azimuthal but singular magnetic field produced by a line current on the axis. Under the constraint of zero normal magnetic field and zero tangential fluid speed at the shock, a set of restricted shock-jump conditions are obtained as functions of the shock Mach number, defined as the ratio of the local shock speed to the unique magnetohydrodynamic wave speed ahead of the shock, and also of a parameter measuring the local strength of the magnetic field. For the line current case, two approaches are explored and the results compared in detail. The first is geometrical shock-dynamics where the restricted shock-jump conditions are applied directly to the equation on the characteristic entering the shock from behind. This gives an ordinary-differential equation for the shock Mach number as a function of radius which is integrated numerically to provide profiles of the shock implosion. Also, analytic, asymptotic results are obtained for the shock trajectory at small radius. The second approach is direct numerical solution of the radially symmetric MHD equations using a shock-capturing method. For the axial magnetic field case the shock implosion is of the Guderley power-law type with exponent that is not affected by the presence of a finite magnetic field. For the axial current case, however, the presence of a tangential magnetic field ahead of the shock with strength inversely proportional to radius introduces a length scale R = \u221a\u03bc_0/p_0I/(2\u03c0) where I is the current, \u03bc_0 is the permeability, and p_0 is the pressure ahead of the shock. For shocks initiated at r \u226b R, shock convergence is first accompanied by shock strengthening as for the strictly gas-dynamic implosion. The diverging magnetic field then slows the shock Mach number growth producing a maximum followed by monotonic reduction towards magnetosonic conditions, even as the shock accelerates toward the axis. A parameter space of initial shock Mach number at a given radius is explored and the implications of the present results for inertial confinement fusion are discussed.", "date": "2014-09", "date_type": "published", "publication": "Physics of Fluids", "volume": "26", "number": "9", "publisher": "American Institute of Physics", "pagerange": "Art. No. 097103", "id_number": "CaltechAUTHORS:20140929-093640759", "issn": "1070-6631", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140929-093640759", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Australian Research Council Discovery Projects funding scheme", "grant_number": "DP120102378" }, { "agency": "Australian Research Council Discovery Early Career Researcher Award", "grant_number": "DE120102942" }, { "agency": "KAUST" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.4894743", "primary_object": { "basename": "1.4894743.pdf", "url": "https://authors.library.caltech.edu/records/9g5bw-rnz75/files/1.4894743.pdf" }, "resource_type": "article", "pub_year": "2014", "author_list": "Pullin, D. I.; Mostert, W.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/a886r-w8j73", "eprint_id": 47067, "eprint_status": "archive", "datestamp": "2023-08-22 12:48:43", "lastmod": "2023-10-26 20:17:13", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Lombardini-M", "name": { "family": "Lombardini", "given": "M." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Meiron-D-I", "name": { "family": "Meiron", "given": "D. I." }, "orcid": "0000-0003-0397-3775" } ] }, "title": "Turbulent mixing driven by spherical implosions. Part 1. Flow description and mixing-layer growth", "ispublished": "pub", "full_text_status": "public", "keywords": "compressible turbulence; shock waves; turbulent mixing", "note": "\u00a9 2014 Cambridge University Press.\n\nReceived 12 June 2013; revised 29 January 2014; accepted 20 March 2014; first published online 28 April 2014.\n\nThis work has been supported in part by the Department of Energy under subcontract no. DE-AC52-06NA25396.\n\nPublished - Lombardini_2014p85.pdf
", "abstract": "We present large-eddy simulations (LES) of turbulent mixing at a perturbed, spherical interface separating two fluids of differing densities and subsequently impacted by a spherically imploding shock wave. This paper focuses on the differences between two fundamental configurations, keeping fixed the initial shock Mach number \u22481.2, the density ratio (precisely |A_0|\u22480.67) and the perturbation shape (dominant spherical wavenumber \u2113_0=40 and amplitude-to-initial radius of 3%): the incident shock travels from the lighter fluid to the heavy fluid or, inversely, from the heavy to the light fluid. After describing the computational problem we present results on the radially symmetric flow, the mean flow, and the growth of the mixing layer. Turbulent statistics are developed in Part 2 (Lombardini, M., Pullin, D. I. & Meiron, D. I. J. Fluid Mech., vol. 748, 2014, pp. 113\u2013142). A wave-diagram analysis of the radially symmetric flow highlights that the light\u2013heavy mixing layer is processed by consecutive reshocks, and not by reverberating rarefaction waves as is usually observed in planar geometry. Less surprisingly, reshocks process the heavy\u2013light mixing layer as in the planar case. In both configurations, the incident imploding shock and the reshocks induce Richtmyer\u2013Meshkov (RM) instabilities at the density layer. However, we observe differences in the mixing-layer growth because the RM instability occurrences, Rayleigh\u2013Taylor (RT) unstable scenarios (due to the radially accelerated motion of the layer) and phase inversion events are different. A small-amplitude stability analysis along the lines of Bell (Los Alamos Scientific Laboratory Report, LA-1321, 1951) and Plesset (J. Appl. Phys., vol. 25, 1954, pp. 96\u201398) helps quantify the effects of the mean flow on the mixing-layer growth by decoupling the effects of RT/RM instabilities from Bell\u2013Plesset effects associated with geometric convergence and compressibility for arbitrary convergence ratios. The analysis indicates that baroclinic instabilities are the dominant effect, considering the low convergence ratio (\u22482) and rather high (\u2113>10) mode numbers considered.", "date": "2014-06", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "748", "publisher": "Cambridge University Press", "pagerange": "85-112", "id_number": "CaltechAUTHORS:20140708-095145766", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140708-095145766", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Department of Energy (DOE)", "grant_number": "DE-AC52-06NA25396" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/jfm.2014.161", "primary_object": { "basename": "Lombardini_2014p85.pdf", "url": "https://authors.library.caltech.edu/records/a886r-w8j73/files/Lombardini_2014p85.pdf" }, "resource_type": "article", "pub_year": "2014", "author_list": "Lombardini, M.; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/mk2d7-7hc14", "eprint_id": 47081, "eprint_status": "archive", "datestamp": "2023-08-22 12:49:01", "lastmod": "2023-10-26 20:18:08", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Lombardini-M", "name": { "family": "Lombardini", "given": "M." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Meiron-D-I", "name": { "family": "Meiron", "given": "D. I." }, "orcid": "0000-0003-0397-3775" } ] }, "title": "Turbulent mixing driven by spherical implosions. Part 2. Turbulence statistics", "ispublished": "pub", "full_text_status": "public", "keywords": "compressible turbulence; shock waves; turbulent mixing", "note": "\u00a9 2014 Cambridge University Press.\nReceived 12 June 2013; revised 29 January 2014; accepted 20 March 2014;first published online 28 April 2014.\nThis work has been supported in part by the Department of Energy under subcontract no. DE-AC52-06NA25396.\n\nPublished - Lombardini_2014p113.pdf
", "abstract": "We present large-eddy simulations (LES) of turbulent mixing at a perturbed, spherical interface separating two fluids of differing densities and subsequently impacted by a spherically imploding shock wave. This paper focuses on the differences between two fundamental configurations, keeping fixed the initial shock Mach number \u2248 1.2, the density ratio (precisely |A_0| \u2248 0.67) and the perturbation shape (dominant spherical wavenumber \u2113_0=40 and amplitude-to-initial radius of 3 %): the incident shock travels from the lighter fluid to the heavy one, or inversely, from the heavy to the light fluid. In Part 1 (Lombardini, M., Pullin, D. I. & Meiron, D. I., J. Fluid Mech., vol. 748, 2014, pp. 85-112), we described the computational problem and presented results on the radially symmetric flow, the mean flow, and the growth of the mixing layer. In particular, it was shown that both configurations reach similar convergence ratios \u22482. Here, turbulent mixing is studied through various turbulence statistics. The mixing activity is first measured through two mixing parameters, the mixing fraction parameter Theta and the effective Atwood ratio A(e), which reach similar late time values in both light-heavy and heavy-light configurations. The Taylor-scale Reynolds numbers attained at late times are estimated \u22482000 in the light-heavy case and 1000 in the heavy-light case. An analysis of the density self-correlation b, a fundamental quantity in the study of variable-density turbulence, shows asymmetries in the mixing layer and non-Boussinesq effects generally observed in high-Reynolds-number Rayleigh-Taylor (RT) turbulence. These traits are more pronounced in the light-heavy mixing layer, as a result of its flow history, in particular because of RT-unstable phases (see Part 1). Another measure distinguishing light-heavy from heavy-light mixing is the velocity-to-scalar Taylor microscales ratio. In particular, at late times, larger values of this ratio are reported in the heavy-light case. The late-time mixing displays the traits some of the traits of the decaying turbulence observed in planar Richtmyer-Meshkov (RM) flows. Only partial isotropization of the flow (in the sense of turbulent kinetic energy (TKE) and dissipation) is observed at late times, the Reynolds normal stresses (and, thus, the directional Taylor microscales) being anisotropic while the directional Kolmogorov microscales approach isotropy. A spectral analysis is developed for the general study of statistically isotropic turbulent fields on a spherical surface, and applied to the present flow. The resulting angular power spectra show the development of an inertial subrange approaching a Kolmogorov-like -5/3 power law at high wavenumbers, similarly to the scaling obtained in planar geometry. It confirms the findings of Thomas & Kares (Phys. Rev. Lett., vol. 109, 2012, 075004) at higher convergence ratios and indicates that the turbulent scales do not seem to feel the effect of the spherical mixing-layer curvature.", "date": "2014-06", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "748", "publisher": "Cambridge University Press", "pagerange": "113-142", "id_number": "CaltechAUTHORS:20140708-150458718", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140708-150458718", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Department of Energy (DOE)", "grant_number": "DE-AC52-06NA25396" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/jfm.2014.163", "primary_object": { "basename": "Lombardini_2014p113.pdf", "url": "https://authors.library.caltech.edu/records/mk2d7-7hc14/files/Lombardini_2014p113.pdf" }, "resource_type": "article", "pub_year": "2014", "author_list": "Lombardini, M.; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/zkp57-mrq61", "eprint_id": 45399, "eprint_status": "archive", "datestamp": "2023-08-20 00:04:29", "lastmod": "2023-10-26 17:58:24", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "L\u00f3pez-Ortega-A", "name": { "family": "L\u00f3pez Ortega", "given": "A." } }, { "id": "Lombardini-M", "name": { "family": "Lombardini", "given": "M." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Meiron-D-I", "name": { "family": "Meiron", "given": "D. I." }, "orcid": "0000-0003-0397-3775" } ] }, "title": "Numerical simulations of the Richtmyer-Meshkov instability in solid-vacuum interfaces using calibrated plasticity laws", "ispublished": "pub", "full_text_status": "public", "note": "\u00a9 2014 American Physical Society.\n\nReceived 4 October 2013; published 28 March 2014.\n\nThis material is based upon work supported by the Department\nof Energy National Nuclear Security Administration under Award No. DE-FC52-08NA28613.\n\nPublished - PhysRevE.89.033018.pdf
", "abstract": "The Richtmyer-Meshkov instability of interfaces separating elastic-plastic materials from vacuum (heavy-light configuration) is studied by means of computational techniques. A fully Eulerian multimaterial algorithm that solves consistently the Euler equations and the time evolution of the deformations in the material is applied to three distinct materials (copper, aluminum, and stainless steel). If a perfectly plastic constitutive relation is considered, an empirical law is computed that relates the long-term perturbation amplitude of the interface, its maximum growth rate, the initial density, and the yield stress of the material. It is shown that this linear relation can be extended to materials that follow more complex plastic behavior which can account for rate dependency, hardening, and thermal softening, and to situations in which small-perturbation theory is no longer valid. In effect, the yield stress computed from measurements of the long-term amplitude and maximum growth rate closely matches the von Mises stress found at the interface of solid materials for a wide range of cases with different initial parameters.", "date": "2014-03-28", "date_type": "published", "publication": "Physical Review E", "volume": "89", "number": "3", "publisher": "American Physical Society", "pagerange": "Art. No. 033018", "id_number": "CaltechAUTHORS:20140501-094156957", "issn": "1539-3755", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140501-094156957", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Department of Energy (DOE) National Nuclear Security Administration", "grant_number": "DE-FC52-08NA28613" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1103/PhysRevE.89.033018", "primary_object": { "basename": "PhysRevE.89.033018.pdf", "url": "https://authors.library.caltech.edu/records/zkp57-mrq61/files/PhysRevE.89.033018.pdf" }, "resource_type": "article", "pub_year": "2014", "author_list": "L\u00f3pez Ortega, A.; Lombardini, M.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/jzdvv-2cj53", "eprint_id": 43153, "eprint_status": "archive", "datestamp": "2023-08-22 11:28:35", "lastmod": "2023-10-25 23:19:10", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "L\u00f3pez-Ortega-A", "name": { "family": "L\u00f3pez Ortega", "given": "A." } }, { "id": "Lombardini-M", "name": { "family": "Lombardini", "given": "M." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Meiron-D-I", "name": { "family": "Meiron", "given": "D. I." }, "orcid": "0000-0003-0397-3775" } ] }, "title": "Numerical simulation of elastic\u2013plastic solid mechanics using an Eulerian stretch tensor approach and HLLD Riemann solver", "ispublished": "pub", "full_text_status": "restricted", "keywords": "Eulerian solid mechanics; Stretch tensor; Approximate multi-material Riemann solver; Richtmyer\u2013Meshkov instability", "note": "\u00a9 2013 Elsevier Inc. \n\nReceived 2 May 2013; Received in revised form 12 September 2013; Accepted 2 October 2013; Available online 10 October 2013. \n\nThis work was supported by the Department of Energy National Nuclear Security Administration under Award No. DE-FC52-08NA28613.", "abstract": "An Eulerian, multi-material numerical method is described for computing dynamic problems involving large deformations in elastic\u2013plastic solids. This approach addresses algorithm failures associated with reconnection and change in topology observed in previously proposed formulations. Among the information contained in the deformation gradients commonly employed for defining constitutive laws suitable for solids, only the symmetric matrix tensor obtained from a polar decomposition of the elastic component of the deformation is required to determine the stress state. The numerical utilization of this symmetric tensor, associated with material stretch, eliminates undesirable, discontinuous deformation states produced by local rigid-body rotations at same-material reconnecting interfaces. Such states appear even where stress states in impacting regions are similar. The temporal evolution of the stretches neither modifies the eigenstructure of the system of equations nor changes its size. We also present a new multi-material approximate Riemann solver based on the HLLD approach, previously applied to other hyperbolic systems, in which waves of distinct velocity exist, for example, as in magnetohydrodynamics. This solver is employed in combination with the modified ghost fluid method (M-GFM) in the description of multi-material interfaces. These composite algorithms enable numerical simulations of the Richtmyer\u2013Meshkov instability (i.e., the instability produced by the interaction of an interface separating materials of different density with a shock wave at an angle) in converging geometries for solid materials that would have previously led to the failure of the method.", "date": "2014-01-15", "date_type": "published", "publication": "Journal of Computational Physics", "volume": "257", "publisher": "Elsevier", "pagerange": "414-441", "id_number": "CaltechAUTHORS:20131223-152813111", "issn": "0021-9991", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131223-152813111", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Department of Energy (DOE) National Nuclear Security Administration", "grant_number": "DE-FC52-08NA28613" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1016/j.jcp.2013.10.007", "resource_type": "article", "pub_year": "2014", "author_list": "L\u00f3pez Ortega, A.; Lombardini, M.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/69xfd-8ce43", "eprint_id": 44405, "eprint_status": "archive", "datestamp": "2023-08-19 23:04:26", "lastmod": "2023-10-26 00:27:20", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Wheatley-V", "name": { "family": "Wheatley", "given": "V." } }, { "id": "Samtaney-Ravi", "name": { "family": "Samtaney", "given": "R." }, "orcid": "0000-0002-4702-6473" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Gehre-R-M", "name": { "family": "Gehre", "given": "R. M." } } ] }, "title": "The transverse field Richtmyer-Meshkov instability in magnetohydrodynamics", "ispublished": "pub", "full_text_status": "public", "note": "\u00a9 2014 American Institute of Physics. Publishing LLC. Received 2 July 2013; accepted 26 November 2013; published online 10 January 2014. Dr. Wheatley is the recipient of an Australian Research Council Discovery Early Career\nResearcher Award (Project No. DE120102942). Additionally, this research was supported under Australian Research Council's Discovery Projects funding scheme (Project No. DP120102378). Professor Samtaney is partially supported by a KAUST Base Research Award.\n\nPublished - 1.4851255.pdf
", "abstract": "The magnetohydrodynamic Richtmyer-Meshkov instability is investigated for the case where the initial magnetic field is unperturbed and aligned with the mean interface location. For this initial condition, the magnetic field lines penetrate the perturbed density interface, forbidding a tangential velocity jump and therefore the presence of a vortex sheet. Through simulation, we find that the vorticity distribution present on the interface immediately after the shock acceleration breaks up into waves traveling parallel and anti-parallel to the magnetic field, which transport the vorticity. The interference of these waves as they propagate causes the perturbation amplitude of the interface to oscillate in time. This interface behavior is accurately predicted over a broad range of parameters by an incompressible linearized model derived presently by solving the corresponding impulse driven, linearized initial value problem. Our use of an equilibrium initial condition results in interface motion produced solely by the impulsive acceleration. Nonlinear compressible simulations are used to investigate the behavior of the transverse field magnetohydrodynamic Richtmyer-Meshkov instability, and the performance of the incompressible model, over a range of shock strengths, magnetic field strengths, perturbation amplitudes and Atwood numbers.", "date": "2014-01-10", "date_type": "published", "publication": "Physics of Fluids", "volume": "26", "number": "1", "publisher": "American Institute of Physics", "pagerange": "Art. No. 016102", "id_number": "CaltechAUTHORS:20140320-095617237", "issn": "1070-6631", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140320-095617237", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Australian Research Council Discovery Early Career Researcher Award", "grant_number": "DE120102942" }, { "agency": "Australian Research Council Discovery Projects funding scheme", "grant_number": "DP120102378" }, { "agency": "KAUST Base Research Award" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.4851255", "primary_object": { "basename": "1.4851255.pdf", "url": "https://authors.library.caltech.edu/records/69xfd-8ce43/files/1.4851255.pdf" }, "resource_type": "article", "pub_year": "2014", "author_list": "Wheatley, V.; Samtaney, R.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/mp64q-x0132", "eprint_id": 43697, "eprint_status": "archive", "datestamp": "2023-08-22 11:00:27", "lastmod": "2023-10-25 23:47:19", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Inoue-M", "name": { "family": "Inoue", "given": "M." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Harun-Z", "name": { "family": "Harun", "given": "Z." } }, { "id": "Marusic-I", "name": { "family": "Marusic", "given": "I." } } ] }, "title": "LES of the adverse-pressure gradient turbulent boundary layer", "ispublished": "pub", "full_text_status": "restricted", "keywords": "Adverse pressure gradient; Turbulent boundary layer; Wall-model LES", "note": "\u00a9 2013 Elsevier Inc.\n\nReceived 7 July 2012;\nReceived in revised form 30 March 2013;\nAccepted 23 June 2013;\nAvailable online 27 July 2013.\n\nThis work has been supported in part by the National Science\nFoundation under Grant CBET-1235605. DIP also acknowledges\ntravel support of the Australian Research Council.", "abstract": "We describe large-eddy simulations (LES) of the flat-plate turbulent boundary layer in the presence of an adverse pressure gradient. The stretched-vortex subgrid-scale model is used in the domain of the flow coupled to a wall model that explicitly accounts for the presence of a finite pressure gradient. The LES are designed to match recent experiments conducted at the University of Melbourne wind tunnel where a plate section with zero pressure gradient is followed by section with constant adverse pressure gradient. First, LES are described at Reynolds numbers based on the local free-stream velocity and the local momentum thickness in the range 6560\u201313,900 chosen to match the experimental conditions. This is followed by a discussion of further LES at Reynolds numbers at approximately 10 times and 100 times these values, which are well out of range of present day direct numerical simulation and wall-resolved LES. For the lower Reynolds number runs, mean velocity profiles, one-point turbulent statistics of the velocity fluctuations, skin friction and the Clauser and acceleration parameters along the streamwise, adverse pressure-gradient domain are compared to the experimental measurements. For the full range of LES, the relationship of the skin-friction coefficient, in the form of the ratio of the local free-stream velocity to the local friction velocity, to both Reynolds number and the Clauser parameter is explored. At large Reynolds numbers, a region of collapse is found that is well described by a simple log-like empirical relationship over two orders of magnitude. This is expected to be useful for constant adverse-pressure gradient flows. It is concluded that the present adverse pressure gradient boundary layers are far from an equilibrium state.", "date": "2013-12", "date_type": "published", "publication": "International Journal of Heat and Fluid Flow", "volume": "44", "publisher": "Elsevier", "pagerange": "293-300", "id_number": "CaltechAUTHORS:20140206-103338989", "issn": "0142-727X", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140206-103338989", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF", "grant_number": "CBET-1235605" }, { "agency": "Australian Research Council (ARC)" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1016/j.ijheatfluidflow.2013.06.011", "resource_type": "article", "pub_year": "2013", "author_list": "Inoue, M.; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/3gwxk-zy210", "eprint_id": 38276, "eprint_status": "archive", "datestamp": "2023-08-22 09:17:19", "lastmod": "2023-10-23 20:00:07", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Barton-Philip-T", "name": { "family": "Barton", "given": "P. T." } }, { "id": "Deiterding-Ralf", "name": { "family": "Deiterding", "given": "R." } }, { "id": "Meiron-D-I", "name": { "family": "Meiron", "given": "D." }, "orcid": "0000-0003-0397-3775" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D." } } ] }, "title": "Eulerian adaptive finite-difference method for high-velocity impact and penetration problems", "ispublished": "pub", "full_text_status": "restricted", "keywords": "Eulerian solid-dynamics; WENO; Adaptive mesh refinement (AMR); Level-sets; Ghost-fluid method; High-velocity impacts", "note": "\u00a9 2013 Elsevier Inc. \n\nReceived 14 March 2012. Received in revised form 17 December 2012. Accepted 11 January 2013. Available online 1 February 2013. \n\nThis material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-FC52-08NA28613.", "abstract": "Owing to the complex processes involved, faithful prediction of high-velocity impact events demands a simulation method delivering efficient calculations based on comprehensively formulated constitutive models. Such an approach is presented herein, employing a weighted essentially non-oscillatory (WENO) method within an adaptive mesh refinement (AMR) framework for the numerical solution of hyperbolic partial differential equations. Applied widely in computational fluid dynamics, these methods are well suited to the involved locally non-smooth finite deformations, circumventing any requirement for artificial viscosity functions for shock capturing. Application of the methods is facilitated through using a model of solid dynamics based upon hyper-elastic theory comprising kinematic evolution equations for the elastic distortion tensor. The model for finite inelastic deformations is phenomenologically equivalent to Maxwell's model of tangential stress relaxation. Closure relations tailored to the expected high-pressure states are proposed and calibrated for the materials of interest. Sharp interface resolution is achieved by employing level-set functions to track boundary motion, along with a ghost material method to capture the necessary internal boundary conditions for material interactions and stress-free surfaces. The approach is demonstrated for the simulation of high velocity impacts of steel projectiles on aluminium target plates in two and three dimensions.", "date": "2013-05-01", "date_type": "published", "publication": "Journal of Computational Physics", "volume": "240", "publisher": "Elsevier", "pagerange": "76-99", "id_number": "CaltechAUTHORS:20130506-071017370", "issn": "0021-9991", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130506-071017370", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Department of Energy (DOE) National Nuclear Security Administration", "grant_number": "DE-FC52-08NA28613" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1016/j.jcp.2013.01.013", "resource_type": "article", "pub_year": "2013", "author_list": "Barton, P. T.; Deiterding, R.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/53aef-ke818", "eprint_id": 37370, "eprint_status": "archive", "datestamp": "2023-08-22 08:06:16", "lastmod": "2023-10-23 17:24:26", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Inoue-M", "name": { "family": "Inoue", "given": "M." } }, { "id": "Saito-N", "name": { "family": "Saito", "given": "N." } } ] }, "title": "On the asymptotic state of high Reynolds number, smooth-wall turbulent flows", "ispublished": "pub", "full_text_status": "public", "keywords": "boundary layer turbulence; wakes", "note": "\u00a9 2013 American Institute of Physics.\n\nReceived 12 September 2012; accepted 15 November 2012; published online 30 January 2013.\n\nThe authors acknowledge helpful discussions with A. Leonard and P. Dimotakis.\n\nPublished - PhysFluids_25_015116.pdf
", "abstract": "It is argued that the extrapolation of the log-wake law for the mean turbulent velocity profile to arbitrarily large Reynolds numbers, and also the similarity scaling for the intensity of stream-wise turbulent velocity fluctuations indicated by recent experimental measurements, are consistent with the hypothesis that smooth-wall turbulence is asymptotically transitory in the sense that these fluctuations almost everywhere decay with respect to the outer velocity scale when 1/log\u2009(Re_\u03c4) \u226a 1, where Re\u03c4 is the Reynolds number based on the skin-friction velocity u_\u03c4. The existence of one or more near-wall maxima in these turbulent velocity fluctuations whose value may grow with Re\u03c4, does not invalidate the main scaling arguments. At gigantic Re_\u03c4, this paradigm suggests that nonlinear motions and \"turbulent\" energy production are still present immediately adjacent to the wall, but that their amplitude becomes vanishingly small compared to the outer velocity scale.", "date": "2013-01", "date_type": "published", "publication": "Physics of Fluids", "volume": "25", "number": "1", "publisher": "American Institute of Physics", "pagerange": "Art. No. 015116", "id_number": "CaltechAUTHORS:20130307-111811197", "issn": "1070-6631", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130307-111811197", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.4774335", "primary_object": { "basename": "PhysFluids_25_015116.pdf", "url": "https://authors.library.caltech.edu/records/53aef-ke818/files/PhysFluids_25_015116.pdf" }, "resource_type": "article", "pub_year": "2013", "author_list": "Pullin, D. I.; Inoue, M.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/arc1e-2j011", "eprint_id": 38253, "eprint_status": "archive", "datestamp": "2023-08-19 14:13:07", "lastmod": "2023-10-23 19:59:01", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Meiron-D-I", "name": { "family": "Meiron", "given": "D. I." }, "orcid": "0000-0003-0397-3775" } ] }, "title": "Philip G. Saffman", "ispublished": "pub", "full_text_status": "restricted", "keywords": "vortex dynamics, low\u2013Reynolds number flow, water waves, turbulence", "note": "\u00a9 2013 by Annual Reviews.\n\nFirst published online as a Review in Advance on\nAugust 16, 2012.\n\nThe authors acknowledge valuable comments, contributions, and insights provided by Ruth Saffman, Louise Wannier, Mark Saffman, Gregory Baker, Stephen Cowley, and Anthony\nPearson.", "abstract": "This article surveys the contributions of Philip Geoffrey Saffman to our\nknowledge of fluid-dynamical phenomena both in nature and in the laboratory.\nWe begin with Saffman's first work on fluid mechanics in Cambridge,\nEngland, in the mid-1950s and then describe the evolution of his ideas and\nresearch, over many diverse areas in fluid mechanics until his final paper in\n2002. It is argued that Saffman brought a unique perspective to our interpretation\nof fluid mechanics as a broad scientific discipline that remains with\nus today.", "date": "2013-01", "date_type": "published", "publication": "Annual Review of Fluid Mechanics", "volume": "45", "publisher": "Annual Reviews", "pagerange": "19-34", "id_number": "CaltechAUTHORS:20130503-085656140", "issn": "0066-4189", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130503-085656140", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1146/annurev-fluid-011212-140655", "resource_type": "article", "pub_year": "2013", "author_list": "Pullin, D. I. and Meiron, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/vmqp3-jqm34", "eprint_id": 34855, "eprint_status": "archive", "datestamp": "2023-08-22 06:07:23", "lastmod": "2023-10-19 22:01:56", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Inoue-M", "name": { "family": "Inoue", "given": "M." } }, { "id": "Mathis-R", "name": { "family": "Mathis", "given": "R." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Inner-layer intensities for the flat-plate turbulent boundary layer combining a predictive wall-model with large-eddy simulations", "ispublished": "pub", "full_text_status": "public", "keywords": "boundary layer turbulence; flow simulation", "note": "\u00a9 2012 American Institute of Physics.\n\nReceived 6 March 2012; accepted 31 May 2012; published online 2 July 2012.\n\nThis work was carried out with the financial support of the Australian Research Council.\n\nPublished - PhysFluids_24_075102.pdf
", "abstract": "Time series velocity signals obtained from large-eddy simulations (LES) within the logarithmic region of the zero-pressure gradient turbulent boundary layer over a smooth wall are used in combination with an empirical, predictive inner-outer wall model [I. Marusic, R. Mathis, and N. Hutchins, \"Predictive model for wall-bounded turbulent flow,\" Science 329, 193 (2010)10.1126/science.1188765] to calculate the statistics of the fluctuating streamwise velocity in the inner region. Results, including spectra and moments up to fourth order, are compared with equivalent predictions using experimental time series, as well as with direct experimental measurements at Reynolds numbers Re_\u03c4 = 7300, 13\u2009600, and 19\u2009000. The LES combined with the wall model are then used to extend the inner-layer predictions to Reynolds numbers Re\u03c4 = 62\u2009000, 100\u2009000, and 200\u2009000 that lie within a gap in log\u2009(Re_\u03c4) space between laboratory measurements and surface-layer, atmospheric experiments. The present results support a loglike increase in the near-wall peak of the streamwise turbulence intensities with Re_\u03c4 and also provide a means of extending LES results at large Reynolds numbers to the near-wall region of wall-bounded turbulent flows.", "date": "2012-07", "date_type": "published", "publication": "Physics of Fluids", "volume": "24", "number": "7", "publisher": "American Institute of Physics", "pagerange": "Art. No. 075102", "id_number": "CaltechAUTHORS:20121011-134705858", "issn": "1070-6631", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20121011-134705858", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Australian Research Council" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.4731299", "primary_object": { "basename": "PhysFluids_24_075102.pdf", "url": "https://authors.library.caltech.edu/records/vmqp3-jqm34/files/PhysFluids_24_075102.pdf" }, "resource_type": "article", "pub_year": "2012", "author_list": "Inoue, M.; Mathis, R.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/z8pa7-pwr58", "eprint_id": 34876, "eprint_status": "archive", "datestamp": "2023-08-22 06:07:27", "lastmod": "2023-10-19 22:03:24", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Saito-N", "name": { "family": "Saito", "given": "Namiko" } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "Dale I." } }, { "id": "Inoue-M", "name": { "family": "Inoue", "given": "Michio" } } ] }, "title": "Large eddy simulation of smooth-wall, transitional and fully rough-wall channel flow", "ispublished": "pub", "full_text_status": "public", "keywords": "boundary layer turbulence; channel flow; drag; flow simulation; surface roughness", "note": "\u00a9 2012 American Institute of Physics.\nReceived 20 February 2012; accepted 5 June 2012; published online 2 July 2012.\nThe authors acknowledge helpful discussions with B. McKeon.\n\nPublished - PhysFluids_24_075103.pdf
", "abstract": "Large eddy simulation (LES) is reported for both smooth and rough-wall channel flows at resolutions for which the roughness is subgrid. The stretched vortex, subgrid-scale model is combined with an existing wall-model that calculates the local friction velocity dynamically while providing a Dirichlet-like slip velocity at a slightly raised wall. This wall model is presently extended to include the effects of subgrid wall roughness by the incorporation of the Hama's roughness function \u0394U^+(k^+_(s\u221e)) that depends on some geometric roughness height k_(s\u221e) scaled in inner variables. Presently Colebrook's empirical roughness function is used but the model can utilize any given function of an arbitrary number of inner-scaled, roughness length parameters. This approach requires no change to the interior LES and can handle both smooth and rough walls. The LES is applied to fully turbulent, smooth, and rough-wall channel flow in both the transitional and fully rough regimes. Both roughness and Reynolds number effects are captured for Reynolds numbers Re_b based on the bulk flow speed in the range 10^4\u201310^(10) with the equivalent Re_\u03c4, based on the wall-drag velocity u_\u03c4 varying from 650 to 10^8. Results include a Moody-like diagram for the friction factor f = f(Re_b, \u2208), \u2208 = k_(s\u221e)/\u03b4, mean velocity profiles, and turbulence statistics. In the fully rough regime, at sufficiently large Re_b, the mean velocity profiles show collapse in outer variables onto a roughness modified, universal, velocity-deficit profile. Outer-flow stream-wise turbulence intensities scale well with u_\u03c4 for both smooth and rough-wall flow, showing a log-like profile. The infinite Reynolds number limits of both smooth and rough-wall flows are explored. An assumption that, for smooth-wall flow, the turbulence intensities scaled on u_\u03c4 are bounded above by the sum of a logarithmic profile plus a finite function across the whole channel suggests that the infinite Re_b limit is inviscid slip flow without turbulence. The asymptote, however, is extremely slow. Turbulent rough-wall flow that conforms to the Hama model shows a finite limit containing turbulence intensities that scale on the friction factor for any small but finite roughness.", "date": "2012-07", "date_type": "published", "publication": "Physics of Fluids", "volume": "24", "number": "7", "publisher": "American Institute of Physics", "pagerange": "Art. No. 075103", "id_number": "CaltechAUTHORS:20121012-121542211", "issn": "1070-6631", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20121012-121542211", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.4731301", "primary_object": { "basename": "PhysFluids_24_075103.pdf", "url": "https://authors.library.caltech.edu/records/z8pa7-pwr58/files/PhysFluids_24_075103.pdf" }, "resource_type": "article", "pub_year": "2012", "author_list": "Saito, Namiko; Pullin, Dale I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/5xnpt-rnr19", "eprint_id": 29487, "eprint_status": "archive", "datestamp": "2023-08-22 04:43:52", "lastmod": "2023-10-24 22:14:44", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Lombardini-M", "name": { "family": "Lombardini", "given": "M." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Meiron-D-I", "name": { "family": "Meiron", "given": "D. I." }, "orcid": "0000-0003-0397-3775" } ] }, "title": "Transition to turbulence in shock-driven mixing:\n a Mach number study", "ispublished": "pub", "full_text_status": "public", "keywords": "shock waves; transition to turbulence; turbulent mixing", "note": "\u00a9 2011 Cambridge University Press.\n\nReceived 8 March 2011; revised 12 July 2011; accepted 25 September 2011; first published online 21 November 2011.\n\nThis work has been supported in part by the Department of Energy under subcontract no. DE-AC52-06NA25396.\n\nPublished - Lombardini2012p17280J_Fluid_Mech.pdf
", "abstract": "Large-eddy simulations of single-shock-driven mixing suggest that, for sufficiently high incident Mach numbers, a two-gas mixing layer ultimately evolves to a late-time,\nfully developed turbulent flow, with Kolmogorov-like inertial subrange following a -5/3 power law. After estimating the kinetic energy injected into the diffuse density layer during the initial shock\u2013interface interaction, we propose a semi-empirical characterization of fully developed turbulence in such flows, based on scale separation, as a function of the initial parameter space, as (\u03b7_(0^+)\u0394u/\u03bd)(\u03b7_(0^+)/L_\u03c1)A^+/\u221a(1-A^(+)^2) \u2273 1.53 \u00d7 10^4/C^2, which corresponds to late-time Taylor-scale Reynolds numbers \u2273250. In this expression, \u03b7_(0^+) represents the post-shock perturbation amplitude, \u0394u the change in interface velocity induced by the shock refraction, \u03bd the characteristic kinematic viscosity of the mixture, L_\u03c1 the inner diffuse thickness of the initial density profile, A^+ the post-shock Atwood ratio, and C(A^+, \u03b7_(0^+)/\u03bb_0)\u22480.3 for the gas combination and post-shock perturbation amplitude considered. The initially perturbed interface separating air and SF_6 (pre-shock Atwood ratio A \u2248 0.67) was impacted in a heavy\u2013light configuration by a shock wave of Mach number M_I = 1.05, 1.25, 1.56, 3.0 or 5.0, for which \u03b7_(0^+) is fixed at about 25% of the dominant wavelength \u03bb_0 of an initial, Gaussian perturbation spectrum. Only partial isotropization of the flow (in the sense of turbulent kinetic energy and dissipation) is observed during the late-time evolution of the mixing zone. For all Mach numbers considered, the late-time flow resembles homogeneous decaying turbulence of Batchelor type, with a turbulent kinetic energy decay exponent n \u2248 1.4 and large-scale (k\u27f60) energy spectrum ~k^4, and a molecular mixing fraction parameter, \u0398 \u2248 0.85. An appropriate time scale characterizing the Taylor-scale Reynolds number decay, as well as the evolution of mixing parameters such as \u0398 and the effective Atwood ratio A_e, seem to indicate the existence of low- and high-Mach-number regimes.", "date": "2012-01-10", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "690", "publisher": "Cambridge University Press", "pagerange": "203-226", "id_number": "CaltechAUTHORS:20120227-122525364", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120227-122525364", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Department of Energy (DOE)", "grant_number": "DE-AC52-06NA25396" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/jfm.2011.425", "primary_object": { "basename": "Lombardini2012p17280J_Fluid_Mech.pdf", "url": "https://authors.library.caltech.edu/records/5xnpt-rnr19/files/Lombardini2012p17280J_Fluid_Mech.pdf" }, "resource_type": "article", "pub_year": "2012", "author_list": "Lombardini, M.; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/x120v-48x50", "eprint_id": 103353, "eprint_status": "archive", "datestamp": "2023-08-22 04:32:33", "lastmod": "2023-10-20 15:57:13", "type": "book_section", "metadata_visibility": "show", "creators": { "items": [ { "id": "L\u00f3pez-Ortega-A", "name": { "family": "L\u00f3pez Ortega", "given": "A." } }, { "id": "Lombardini-M", "name": { "family": "Lombardini", "given": "M." } }, { "id": "Hill-D-J", "name": { "family": "Hill", "given": "D. J." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Meiron-D-I", "name": { "family": "Meiron", "given": "D. I." }, "orcid": "0000-0003-0397-3775" } ] }, "title": "Shock Dynamics for Cylindrical/Spherical Converging Shocks in Elastic-Plastic Solids", "ispublished": "unpub", "full_text_status": "restricted", "keywords": "Mach Number; Plastic Region; Elastic Precursor; Eulerian Description; Converge Shock Wave", "note": "\u00a9 2012 Springer-Verlag Berlin Heidelberg. \n\nThis material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-FC52-08NA28613.", "abstract": "The study of cylindrical and spherical converging shock waves propagating in solid materials is relevant to the production of high temperatures and pressures in condensed matter with applications to inertial confinement fusion [1]. However, experimental studies conducted in the area are prone to complications derived from the measurement techniques available and the difficulty of producing a quasi-radially symmetric flow.", "date": "2012", "date_type": "published", "publisher": "Springer", "place_of_pub": "Berlin", "pagerange": "757-763", "id_number": "CaltechAUTHORS:20200520-110119540", "isbn": "978-3-642-25684-4", "book_title": "28th International Symposium on Shock Waves", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200520-110119540", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Department of Energy (DOE)", "grant_number": "DE-FC52-08NA28613" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "contributors": { "items": [ { "id": "Kontis-K", "name": { "family": "Kontis", "given": "Konstantinos" } } ] }, "doi": "10.1007/978-3-642-25685-1_115", "resource_type": "book_section", "pub_year": "2012", "author_list": "L\u00f3pez Ortega, A.; Lombardini, M.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/e8qgz-kz767", "eprint_id": 28613, "eprint_status": "archive", "datestamp": "2023-08-19 08:31:42", "lastmod": "2023-10-24 18:01:18", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Inoue-M", "name": { "family": "Inoue", "given": "M." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Large-eddy simulation of the zero-pressure-gradient turbulent boundary layer up to Re_\u03b8 = O(10^(12))", "ispublished": "pub", "full_text_status": "public", "keywords": "turbulence modelling, turbulence simulation, turbulent boundary layers", "note": "\u00a9 2011 Cambridge University Press. Received 14 February 2011; revised 5 August 2011; accepted 7 August 2011; first published online 29 September 2011. This work has been supported in part by the National Science Foundation under\nGrant DMS-0714050. Helpful discussions with I. Marusic and B. McKeon are acknowledged.\n\nPublished - Inoue2011p16557J_Fluid_Mech.pdf
", "abstract": "A near-wall subgrid-scale (SGS) model is used to perform large-eddy simulation (LES) of the developing, smooth-wall, zero-pressure-gradient flat-plate turbulent boundary layer. In this model, the stretched-vortex, SGS closure is utilized in conjunction with a tailored, near-wall model designed to incorporate anisotropic vorticity scales in the presence of the wall. Large-eddy simulations of the turbulent boundary layer are reported at Reynolds numbers Re\u03b8 based on the free-stream velocity and the momentum thickness in the range Re_\u03b8 = 10^3-10^(12). Results include the inverse square-root skin-friction coefficient, \u221a2/Cf, velocity profiles, the shape factor H, the von K\u00e1rm\u00e1n 'constant' and the Coles wake factor as functions of Re_\u03b8. Comparisons with some direct numerical simulation (DNS) and experiment are made including turbulent intensity data from atmospheric-layer measurements at Re_\u03b8 = O(10^6). At extremely large Re_\u03b8, the empirical Coles\u2013Fernholz relation for skin-friction coefficient provides a reasonable representation of the LES predictions. While the present LES methodology cannot probe the structure of the near-wall region, the present results show turbulence intensities that scale on the wall-friction velocity and on the Clauser length scale over almost all of the outer boundary layer. It is argued that LES is suggestive of the asymptotic, infinite Reynolds number limit for the smooth-wall turbulent boundary layer and different ways in which this limit can be approached are discussed. The maximum Re_\u03b8 of the present simulations appears to be limited by machine precision and it is speculated, but not demonstrated, that even larger Re_\u03b8 could be achieved with quad- or higher-precision arithmetic.", "date": "2011-11", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "686", "publisher": "Cambridge University Press", "pagerange": "507-533", "id_number": "CaltechAUTHORS:20120103-113141281", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120103-113141281", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF", "grant_number": "DMS-0714050" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/jfm.2011.342", "primary_object": { "basename": "Inoue2011p16557J_Fluid_Mech.pdf", "url": "https://authors.library.caltech.edu/records/e8qgz-kz767/files/Inoue2011p16557J_Fluid_Mech.pdf" }, "resource_type": "article", "pub_year": "2011", "author_list": "Inoue, M. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/vv35h-35c03", "eprint_id": 31590, "eprint_status": "archive", "datestamp": "2023-08-22 03:52:38", "lastmod": "2023-10-17 18:42:04", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Yang-Y", "name": { "family": "Yang", "given": "Yue" } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Evolution of vortex-surface fields in viscous Taylor-Green and Kida-Pelz flows", "ispublished": "pub", "full_text_status": "public", "keywords": "topological fluid dynamics; turbulence theory; vortex dynamics", "note": "\u00a9 2012 Cambridge University Press. Received 23 January 2011; revised 22 June 2011; accepted 25 June 2011.\nPublished online: 06 October 2011. This work has been supported in part by the National Science Foundation under\ngrant DMS-1016111.\n\nPublished - Yang2011p18233J_Fluid_Mech.pdf
", "abstract": "In order to investigate continuous vortex dynamics based on a Lagrangian-like formulation, we develop a theoretical framework and a numerical method for computation of the evolution of a vortex-surface field (VSF) in viscous incompressible flows with simple topology and geometry. Equations describing the continuous, timewise evolution of a VSF from an existing VSF at an initial time are first reviewed. Non-uniqueness in this formulation is resolved by the introduction of a pseudo-time and a corresponding pseudo-evolution in which the evolved field is 'advected' by frozen vorticity onto a VSF. A weighted essentially non-oscillatory (WENO) method is used to solve the pseudo-evolution equations in pseudo-time, providing a dissipative-like regularization. Vortex surfaces are then extracted as iso-surfaces of the VSFs at different real physical times. The method is applied to two viscous flows with Taylor\u2013Green and Kida\u2013Pelz initial conditions respectively. Results show the collapse of vortex surfaces, vortex reconnection, the formation and roll-up of vortex tubes, vorticity intensification between anti-parallel vortex tubes, and vortex stretching and twisting. A possible scenario for understanding the transition from a smooth laminar flow to turbulent flow in terms of topology of vortex surfaces is discussed.", "date": "2011-10", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "685", "publisher": "Cambridge University Press", "pagerange": "146-164", "id_number": "CaltechAUTHORS:20120522-101105941", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120522-101105941", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF", "grant_number": "DMS-1016111" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/jfm.2011.287", "primary_object": { "basename": "Yang2011p18233J_Fluid_Mech.pdf", "url": "https://authors.library.caltech.edu/records/vv35h-35c03/files/Yang2011p18233J_Fluid_Mech.pdf" }, "resource_type": "article", "pub_year": "2011", "author_list": "Yang, Yue and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/4w3ce-y2g94", "eprint_id": 28417, "eprint_status": "archive", "datestamp": "2023-08-22 03:51:10", "lastmod": "2023-10-24 17:52:52", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Yang-Y", "name": { "family": "Yang", "given": "Yue" } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Evolution of vortex-surface fields in viscous Taylor\u2013Green and Kida\u2013Pelz flows", "ispublished": "pub", "full_text_status": "public", "keywords": "topological fluid dynamics; turbulence theory; vortex dynamics", "note": "\u00a9 2011 Cambridge University Press. Received 23 January 2011; revised 22 June 2011; accepted 25 June 2011.\nOnline publication October 06 2011. This work has been supported in part by the National Science Foundation under\ngrant DMS-1016111.\n\nPublished - Yang2011p16454J_Fluid_Mech.pdf
", "abstract": "In order to investigate continuous vortex dynamics based on a Lagrangian-like formulation, we develop a theoretical framework and a numerical method for computation of the evolution of a vortex-surface field (VSF) in viscous incompressible flows with simple topology and geometry. Equations describing the continuous, timewise evolution of a VSF from an existing VSF at an initial time are first reviewed. Non-uniqueness in this formulation is resolved by the introduction of a pseudo-time and a corresponding pseudo-evolution in which the evolved field is 'advected' by frozen vorticity onto a VSF. A weighted essentially non-oscillatory (WENO) method is used to solve the pseudo-evolution equations in pseudo-time, providing a dissipative-like regularization. Vortex surfaces are then extracted as iso-surfaces of the VSFs at different real physical times. The method is applied to two viscous flows with Taylor\u2013Green and Kida\u2013Pelz initial conditions respectively. Results show the collapse of vortex surfaces, vortex reconnection, the formation and roll-up of vortex tubes, vorticity intensification between anti-parallel vortex tubes, and vortex stretching and twisting. A possible scenario for understanding the transition from a smooth laminar flow to turbulent flow in terms of topology of vortex surfaces is discussed.", "date": "2011-10", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "685", "publisher": "Cambridge University Press", "pagerange": "146-164", "id_number": "CaltechAUTHORS:20111212-100604994", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20111212-100604994", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF", "grant_number": "DMS-1016111" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/jfm.2011.287", "primary_object": { "basename": "Yang2011p16454J_Fluid_Mech.pdf", "url": "https://authors.library.caltech.edu/records/4w3ce-y2g94/files/Yang2011p16454J_Fluid_Mech.pdf" }, "resource_type": "article", "pub_year": "2011", "author_list": "Yang, Yue and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/jap9z-fx982", "eprint_id": 25443, "eprint_status": "archive", "datestamp": "2023-08-22 03:28:10", "lastmod": "2023-10-24 15:52:35", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Ziegler-J-L", "name": { "family": "Ziegler", "given": "Jack L." } }, { "id": "Deiterding-R", "name": { "family": "Deiterding", "given": "Ralf" } }, { "id": "Shepherd-J-E", "name": { "family": "Shepherd", "given": "Joseph E." }, "orcid": "0000-0003-3181-9310" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "An adaptive high-order hybrid scheme for compressive, viscous flows with detailed chemistry", "ispublished": "pub", "full_text_status": "public", "keywords": "Weighted essentially non-oscillatory; Detonation; Adaptive mesh refinement; Navier\u2013Stokes; Direct numerical simulation; Reacting compressible flow", "note": "\u00a9 2011 Elsevier Inc.\n\nReceived 18 June 2010; revised 16 June 2011; Accepted 16 June 2011. Available online 25 June 2011.\n\nJack Ziegler is supported by the Department of Energy Computational Science Graduate Fellowship program (DOE CSGF).\nThis research used resources of the National Energy Research Scientific Computing (NERSC) Center. D. Pullin and R. Deiterding\nwere partially supported by the Department of Energy Advanced Scientific and Computing (ASC) program under subcontract\nB341492 of DOE contract W-7405-ENG-48.\n\nAccepted Version - ziegler_jcp_2011.pdf
", "abstract": "A hybrid weighted essentially non-oscillatory (WENO)/centered-difference numerical method, with low numerical dissipation, high-order shock-capturing, and structured adaptive mesh refinement (SAMR), has been developed for the direct numerical simulation of the multicomponent, compressible, reactive Navier\u2013Stokes equations. The method enables accurate resolution of diffusive processes within reaction zones. The approach combines time-split reactive source terms with a high-order, shock-capturing scheme specifically designed for diffusive flows. A description of the order-optimized, symmetric, finite difference, flux-based, hybrid WENO/centered-difference scheme is given, along with its implementation in a high-order SAMR framework. The implementation of new techniques for discontinuity flagging, scheme-switching, and high-order prolongation and restriction is described. In particular, the refined methodology does not require upwinded WENO at grid refinement interfaces for stability, allowing high-order prolongation and thereby eliminating a significant source of numerical diffusion within the overall code performance. A series of one-and two-dimensional test problems is used to verify the implementation, specifically the high-order accuracy of the diffusion terms. One-dimensional benchmarks include a viscous shock wave and a laminar flame. In two-space dimensions, a Lamb\u2013Oseen vortex and an unstable diffusive detonation are considered, for which quantitative convergence is demonstrated. Further, a two-dimensional high-resolution simulation of a reactive Mach reflection phenomenon with diffusive multi-species mixing is presented.", "date": "2011-08-20", "date_type": "published", "publication": "Journal of Computational Physics", "volume": "230", "number": "20", "publisher": "Elsevier", "pagerange": "7598-7630", "id_number": "CaltechAUTHORS:20110927-090740849", "issn": "0021-9991", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110927-090740849", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Department of Energy (DOE)", "grant_number": "B341492" }, { "agency": "Department of Energy (DOE)", "grant_number": "W-7405-ENG-48" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1016/j.jcp.2011.06.016", "primary_object": { "basename": "ziegler_jcp_2011.pdf", "url": "https://authors.library.caltech.edu/records/jap9z-fx982/files/ziegler_jcp_2011.pdf" }, "resource_type": "article", "pub_year": "2011", "author_list": "Ziegler, Jack L.; Deiterding, Ralf; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/m9em4-5xh42", "eprint_id": 25223, "eprint_status": "archive", "datestamp": "2023-08-19 07:18:39", "lastmod": "2023-10-24 15:42:51", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Ward-G-M", "name": { "family": "Ward", "given": "G. M." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "A study of planar Richtmyer-Meshkov instability in fluids with Mie-Gr\u00fcneisen equations of state", "ispublished": "pub", "full_text_status": "public", "keywords": "equations of state, flow instability, fluid oscillations, Mach number, mesh generation, shock wave effects, supersonic flow, vortices", "note": "\u00a9 2011 American Institute of Physics. Received 28 June 2010; accepted 23 May 2011; published online 15 July 2011.\n\nPublished - Ward2011p15654Phys_Fluids.pdf
", "abstract": "We present a numerical comparison study of planar Richtmyer-Meshkov instability with the intention of exposing the role of the equation of state. Results for Richtmyer-Meshkov instability in fluids with Mie-Gr\u00fcneisen equations of state derived from a linear shock-particle speed Hugoniot relationship (Jeanloz, J. Geophys. Res. 94, 5873, 1989; McQueen et al., High Velocity Impact Phenomena (1970), pp. 294\u2013417; Menikoff and Plohr, Rev. Mod. Phys. 61(1), 75 1989) are compared to those from perfect gases under nondimensionally matched initial conditions at room temperature and pressure. The study was performed using Caltech's Adaptive Mesh Refinement, Object-oriented C++ (AMROC) (Deiterding, Adaptive Mesh Refinement: Theory and Applications (2005), Vol. 41, pp. 361\u2013372; Deiterding, \"Parallel adaptive simulation of multi-dimensional detonation structures,\" Ph.D. thesis (Brandenburgische Technische Universit\u00e4t Cottbus, September 2003)) framework with a low-dissipation, hybrid, center-difference, limiter patch solver (Ward and Pullin, J. Comput. Phys. 229, 2999 (2010)). Results for single and triple mode planar Richtmyer-Meshkov instability when a reflected shock wave occurs are first examined for mid-ocean ridge basalt (MORB) and molybdenum modeled by Mie-Gr\u00fcneisen equations of state. The single mode case is examined for incident shock Mach numbers of 1.5 and 2.5. The planar triple mode case is studied using a single incident Mach number of 2.5 with initial corrugation wavenumbers related by k_1 = k_2+k_3. Comparison is then drawn to Richtmyer-Meshkov instability in perfect gases with matched nondimensional pressure jump across the incident shock, post-shock Atwood ratio, post-shock amplitude-to-wavelength ratio, and time nondimensionalized by Richtmyer's linear growth time constant prediction. Differences in start-up time and growth rate oscillations are observed across equations of state. Growth rate oscillation frequency is seen to correlate directly to the oscillation frequency for the transmitted and reflected shocks. For the single mode cases, further comparison is given for vorticity distribution and corrugation centerline shortly after shock interaction. Additionally, we examine single mode Richtmyer-Meshkov instability when a reflected expansion wave is present for incident Mach numbers of 1.5 and 2.5. Comparison to perfect gas solutions in such cases yields a higher degree of similarity in start-up time and growth rate oscillations. The formation of incipient weak waves in the heavy fluid driven by waves emanating from the perturbed transmitted shock is observed when an expansion wave is reflected.", "date": "2011-07", "date_type": "published", "publication": "Physics of Fluids", "volume": "23", "number": "7", "publisher": "American Institute of Physics", "pagerange": "Art. No. 076101", "id_number": "CaltechAUTHORS:20110906-081413985", "issn": "1070-6631", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110906-081413985", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.3607444", "primary_object": { "basename": "Ward2011p15654Phys_Fluids.pdf", "url": "https://authors.library.caltech.edu/records/m9em4-5xh42/files/Ward2011p15654Phys_Fluids.pdf" }, "resource_type": "article", "pub_year": "2011", "author_list": "Ward, G. M. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/0sffc-77w81", "eprint_id": 23791, "eprint_status": "archive", "datestamp": "2023-08-22 02:38:59", "lastmod": "2023-10-23 20:00:54", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Yang-Yue", "name": { "family": "Yang", "given": "Yue" } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Geometric study of Lagrangian and Eulerian structures in turbulent channel flow", "ispublished": "pub", "full_text_status": "public", "keywords": "boundary layer structure; turbulence theory; turbulent boundary layers", "note": "\u00a9 2011 Cambridge University Press. \n\nReceived 9 August 2010; revised 7 December 2010; accepted 13 December 2010; first published online 2 March 2011. \n\nThe authors are grateful to P. Koumoutsakos for providing generous access on the Brutus cluster at the ETH Zurich. The authors thank I. Bermejo-Moreno and D. Chung for helpful comments. This work has been supported in part by the National Science Foundation under grant DMS-1016111.\n\nPublished - Yang2011p13906J_Fluid_Mech.pdf
", "abstract": "We report the detailed multi-scale and multi-directional geometric study of both evolving Lagrangian and instantaneous Eulerian structures in turbulent channel flow at low and moderate Reynolds numbers. The Lagrangian structures (material surfaces) are obtained by tracking the Lagrangian scalar field, and Eulerian structures are extracted from the swirling strength field at a time instant. The multi-scale and multi-directional geometric analysis, based on the mirror-extended curvelet transform, is developed to quantify the geometry, including the averaged inclination and sweep angles, of both structures at up to eight scales ranging from the half-height \u03b4 of the channel to several viscous length scales \u03b4_\u03bd. Here, the inclination angle is on the plane of the streamwise and wall-normal directions, and the sweep angle is on the plane of streamwise and spanwise directions. The results show that coherent quasi-streamwise structures in the near-wall region are composed of inclined objects with averaged inclination angle 35\u00b0\u201345\u00b0, averaged sweep angle 30\u00b0\u201340\u00b0 and characteristic scale 20\u03b4_\u03bd, and 'curved legs' with averaged inclination angle 20\u00b0\u201330\u00b0, averaged sweep angle 15\u00b0\u201330\u00b0 and length scale 5\u03b4_\u03bd\u201310\u03b4_\u03bd. The temporal evolution of Lagrangian structures shows increasing inclination and sweep angles with time, which may correspond to the lifting process of near-wall quasi-streamwise vortices. The large-scale structures that appear to be composed of a number of individual small-scale objects are detected using cross-correlations between Eulerian structures with large and small scales. These packets are located at the near-wall region with the typical height 0.25\u03b4 and may extend over 10\u03b4 in the streamwise direction in moderate-Reynolds-number, long channel flows. In addition, the effects of the Reynolds number and comparisons between Lagrangian and Eulerian structures are discussed.", "date": "2011-05", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "674", "publisher": "Cambridge University Press", "pagerange": "67-92", "id_number": "CaltechAUTHORS:20110525-093417744", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110525-093417744", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF", "grant_number": "DMS-1016111" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/S0022112010006427", "primary_object": { "basename": "Yang2011p13906J_Fluid_Mech.pdf", "url": "https://authors.library.caltech.edu/records/0sffc-77w81/files/Yang2011p13906J_Fluid_Mech.pdf" }, "resource_type": "article", "pub_year": "2011", "author_list": "Yang, Yue and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/0ttbd-7yw03", "eprint_id": 23408, "eprint_status": "archive", "datestamp": "2023-08-22 02:33:15", "lastmod": "2023-10-23 19:33:24", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "van-Rees-W-M", "name": { "family": "van Rees", "given": "Wim M." } }, { "id": "Leonard-A", "name": { "family": "Leonard", "given": "Anthony" } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Koumoutsakos-P", "name": { "family": "Koumoutsakos", "given": "Petros" } } ] }, "title": "A comparison of vortex and pseudo-spectral methods for the simulation of periodic vortical flows at high Reynolds numbers", "ispublished": "pub", "full_text_status": "restricted", "keywords": "Vortex method; Pseudo-spectral method; Vortical flow; Vortex reconnection", "note": "\u00a9 2010 Elsevier Inc.\n\nReceived 13 August 2010; revised 18 November 2010; accepted 19 November 2010. Available online 9 December 2010.\n\nWe wish to acknowledge many helpful discussions with Yue Yang (Caltech) during the course of this work.", "abstract": "We present a validation study for the hybrid particle-mesh vortex method against a pseudo-spectral method for the Taylor\u2013Green vortex at Re_\u0393 = 1600 as well as in the collision of two antiparallel vortex tubes at Re_\u0393 = 10,000. In this study we present diagnostics such as energy spectra and enstrophy as computed by both methods as well as point-wise comparisons of the vorticity field. Using a fourth order accurate kernel for interpolation between the particles and the mesh, the results of the hybrid vortex method and of the pseudo-spectral method agree well in both flow cases. For the Taylor\u2013Green vortex, the vorticity contours computed by both methods around the time of the energy dissipation peak overlap. The energy spectrum shows that only the smallest length scales in the flow are not captured by the vortex method.\nIn the second flow case, where we compute the collision of two anti-parallel vortex tubes at Reynolds number 10,000, the vortex method results and the pseudo-spectral method results are in very good agreement up to and including the first reconnection of the tubes. The maximum error in the effective viscosity is about 2.5% for the vortex method and about 1% for the pseudo-spectral method. At later times the flows computed with the different methods show the same qualitative features, but the quantitative agreement on vortical structures is lost.", "date": "2011-04-20", "date_type": "published", "publication": "Journal of Computational Physics", "volume": "230", "number": "8", "publisher": "Elsevier", "pagerange": "2794-2805", "id_number": "CaltechAUTHORS:20110421-100240833", "issn": "0021-9991", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110421-100240833", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1016/j.jcp.2010.11.031", "resource_type": "article", "pub_year": "2011", "author_list": "van Rees, Wim M.; Leonard, Anthony; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/edzkw-ybj91", "eprint_id": 23079, "eprint_status": "archive", "datestamp": "2023-08-22 02:09:52", "lastmod": "2023-10-23 17:53:55", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Lombardini-M", "name": { "family": "Lombardini", "given": "M." } }, { "id": "Hill-D-J", "name": { "family": "Hill", "given": "D. J." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Meiron-D-I", "name": { "family": "Meiron", "given": "D. I." }, "orcid": "0000-0003-0397-3775" } ] }, "title": "Atwood ratio dependence of Richtmyer-Meshkov flows under reshock conditions using large-eddy simulations", "ispublished": "pub", "full_text_status": "public", "keywords": "instability; shock waves; turbulent mixing", "note": "\u00a9 2011 Cambridge University Press. \n\nReceived 11 January 2010; revised 18 September 2010; accepted 8 October 2010; first published online 1 February 2011. \n\nThis work has been supported in part by the Department of Energy under subcontract no. DE-AC52-06NA25396.\n\nPublished - Lombardini2011p13110J_Fluid_Mech.pdf
", "abstract": "We study the shock-driven turbulent mixing that occurs when a perturbed planar density interface is impacted by a planar shock wave of moderate strength and subsequently reshocked. The present work is a systematic study of the influence of the relative molecular weights of the gases in the form of the initial Atwood ratio A. We investigate the cases A = \u00b1 0.21, \u00b10.67 and \u00b10.87 that correspond to the realistic gas combinations air\u2013CO_2, air\u2013SF_6 and H_2\u2013air. A canonical, three-dimensional numerical experiment, using the large-eddy simulation technique with an explicit subgrid model, reproduces the interaction within a shock tube with an endwall where the incident shock Mach number is ~1.5 and the initial interface perturbation has a fixed dominant wavelength and a fixed amplitude-to-wavelength ratio ~0.1. For positive Atwood configurations, the reshock is followed by secondary waves in the form of alternate expansion and compression waves travelling between the endwall and the mixing zone. These reverberations are shown to intensify turbulent kinetic energy and dissipation across the mixing zone. In contrast, negative Atwood number configurations produce multiple secondary reshocks following the primary reshock, and their effect on the mixing region is less pronounced. As the magnitude of A is increased, the mixing zone tends to evolve less symmetrically. The mixing zone growth rate following the primary reshock approaches a linear evolution prior to the secondary wave interactions. When considering the full range of examined Atwood numbers, measurements of this growth rate do not agree well with predictions of existing analytic reshock models such as the model by Mikaelian (Physica D, vol. 36, 1989, p. 343). Accordingly, we propose an empirical formula and also a semi-analytical, impulsive model based on a diffuse-interface approach to describe the A-dependence of the post-reshock growth rate.", "date": "2011-03", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "670", "publisher": "Cambridge University Press", "pagerange": "439-480", "id_number": "CaltechAUTHORS:20110323-142306126", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110323-142306126", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Department of Energy (DOE)", "grant_number": "DE-AC52-06NA25396" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/S0022112010005367", "primary_object": { "basename": "Lombardini2011p13110J_Fluid_Mech.pdf", "url": "https://authors.library.caltech.edu/records/edzkw-ybj91/files/Lombardini2011p13110J_Fluid_Mech.pdf" }, "resource_type": "article", "pub_year": "2011", "author_list": "Lombardini, M.; Hill, D. J.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/4tha9-8x095", "eprint_id": 22605, "eprint_status": "archive", "datestamp": "2023-08-22 01:34:14", "lastmod": "2023-10-23 17:03:10", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Hill-D-J", "name": { "family": "Hill", "given": "D. J." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D." } }, { "id": "Ortiz-M", "name": { "family": "Ortiz", "given": "M." }, "orcid": "0000-0001-5877-4824" }, { "id": "Meiron-D-I", "name": { "family": "Meiron", "given": "D." }, "orcid": "0000-0003-0397-3775" } ] }, "title": "An Eulerian hybrid WENO centered-difference solver for elastic-plastic solids", "ispublished": "pub", "full_text_status": "restricted", "keywords": "Hyper-elasticity; Plasticity; Finite-difference; WENO; Eulerian", "note": "\u00a9 2010 Elsevier Inc. Received 26 February 2010; revised 23 July 2010; accepted 16 August 2010. Available online 27 August 2010.", "abstract": "We present a finite-difference based solver for hyper-elastic and viscoplastic systems using a hybrid of the weighted essentially non-oscillatory (WENO) schemes combined with explicit centered difference to solve the equations of motion expressed in an Eulerian formulation. By construction our approach minimizes both numerical dissipation errors and the creation of curl-constraint violating errors away from discontinuities while avoiding\nthe calculation of hyperbolic characteristics often needed in general finite-volume schemes. As a result of the latter feature, the formulation allows for a wide range of\nconstitutive relations and only an upper-bound on the speed of sound at each time is required to ensure a stable timestep is chosen. Several one- and two-dimensional examples are presented using a range of constitutive laws with and without additional plastic modeling. In addition we extend the reflection technique combined with ghost-cells to enforce fixed boundaries with a zero tangential stress condition (i.e. free-slip).", "date": "2010-12-10", "date_type": "published", "publication": "Journal of Computational Physics", "volume": "229", "number": "24", "publisher": "Elsevier", "pagerange": "9053-9072", "id_number": "CaltechAUTHORS:20110302-102610242", "issn": "0021-9991", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110302-102610242", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1016/j.jcp.2010.08.020", "resource_type": "article", "pub_year": "2010", "author_list": "Hill, D. J.; Pullin, D.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/7dn0c-phz56", "eprint_id": 21181, "eprint_status": "archive", "datestamp": "2023-08-22 01:10:17", "lastmod": "2023-10-20 23:49:08", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Yang-Yue", "name": { "family": "Yang", "given": "Yue" } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "On Lagrangian and vortex-surface fields for flows with Taylor\u2013Green and Kida\u2013Pelz initial conditions", "ispublished": "pub", "full_text_status": "public", "keywords": "topological fluid dynamics; turbulence theory; vortex dynamics", "note": "\u00a9 2010 Cambridge University Press. \n\nReceived 16 February 2010; revised 31 May 2010; accepted 1 June 2010. \n\nThis work has been supported in part by the National Science Foundation under Grant DMS-0714050.\n\nPublished - Yang2010p12026J_Fluid_Mech.pdf
", "abstract": "For a strictly inviscid barotropic flow with conservative body forces, the Helmholtz vorticity theorem shows that material or Lagrangian surfaces which are vortex surfaces at time t = 0 remain so for t > 0. In this study, a systematic methodology is developed for constructing smooth scalar fields \u03c6(x, y, z, t = 0) for Taylor\u2013Green and Kida\u2013Pelz velocity fields, which, at t = 0, satisfy \u03c9\u00b7\u2207\u03c6 = 0. We refer to such fields as vortex-surface fields. Then, for some constant C, iso-surfaces \u03c6 = C define vortex surfaces. It is shown that, given the vorticity, our definition of a vortex-surface field admits non-uniqueness, and this is presently resolved numerically using an optimization approach. Additionally, relations between vortex-surface fields and the classical Clebsch representation are discussed for flows with zero helicity. Equations describing the evolution of vortex-surface fields are then obtained for both inviscid and viscous incompressible flows. Both uniqueness and the distinction separating the evolution of vortex-surface fields and Lagrangian fields are discussed. By tracking \u03c6 as a Lagrangian field in slightly viscous flows, we show that the well-defined evolution of Lagrangian surfaces that are initially vortex surfaces can be a good approximation to vortex surfaces at later times prior to vortex reconnection. In the evolution of such Lagrangian fields, we observe that initially blob-like vortex surfaces are progressively stretched to sheet-like shapes so that neighbouring portions approach each other, with subsequent rolling up of structures near the interface, which reveals more information on dynamics than the iso-surfaces of vorticity magnitude. The non-local geometry in the evolution is quantified by two differential geometry properties. Rolled-up local shapes are found in the Lagrangian structures that were initially vortex surfaces close to the time of vortex reconnection. It is hypothesized that this is related to the formation of the very high vorticity regions.", "date": "2010-10-25", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "661", "publisher": "Cambridge University Press", "pagerange": "446-481", "id_number": "CaltechAUTHORS:20101206-105702294", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101206-105702294", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF", "grant_number": "DMS-0714050" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/S0022112010003125", "primary_object": { "basename": "Yang2010p12026J_Fluid_Mech.pdf", "url": "https://authors.library.caltech.edu/records/7dn0c-phz56/files/Yang2010p12026J_Fluid_Mech.pdf" }, "resource_type": "article", "pub_year": "2010", "author_list": "Yang, Yue and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/hz9g1-h9097", "eprint_id": 19286, "eprint_status": "archive", "datestamp": "2023-08-19 03:08:54", "lastmod": "2023-10-20 20:30:32", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Yang-Yue", "name": { "family": "Yang", "given": "Yue" } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Bermejo-Moreno-I", "name": { "family": "Bermejo-Moreno", "given": "Iv\u00e1n" } } ] }, "title": "Multi-scale geometric analysis of Lagrangian structures in isotropic turbulence", "ispublished": "pub", "full_text_status": "public", "note": "\u00a9 2010 Cambridge University Press. \n\nReceived 20 July 2009; revised 27 January 2010; accepted 28 January 2010; first published online 17 May 2010. \n\nThis work has been supported in part by the National Science Foundation under grant DMS-0714050. D. I. Pullin benefited from support during a visit to the Center for Water Research at the University of Western Australia.\n\nPublished - Yang2010p10836J_Fluid_Mech.pdf
", "abstract": "We report the multi-scale geometric analysis of Lagrangian structures in forced isotropic turbulence and also with a frozen turbulent field. A particle backward-tracking method, which is stable and topology preserving, was applied to obtain the Lagrangian scalar field \u03c6 governed by the pure advection equation in the Eulerian form \u2202_t\u03c6 + u \u00b7 \u2207\u03c6 = 0. The temporal evolution of Lagrangian structures was first obtained by extracting iso-surfaces of \u03c6 with resolution 1024^3 at different times, from t = 0 to t = T_e, where T_e is the eddy turnover time. The surface area growth rate of the Lagrangian structure was quantified and the formation of stretched and rolled-up structures was observed in straining regions and stretched vortex tubes, respectively. The multi-scale geometric analysis of Bermejo-Moreno & Pullin (J. Fluid Mech., vol. 603, 2008, p. 101) has been applied to the evolution of \u03c6 to extract structures at different length scales and to characterize their non-local geometry in a space of reduced geometrical parameters. In this multi-scale sense, we observe, for the evolving turbulent velocity field, an evolutionary breakdown of initially large-scale Lagrangian structures that first distort and then either themselves are broken down or stretched laterally into sheets. Moreover, after a finite time, this progression appears to be insensible to the form of the initially smooth Lagrangian field. In comparison with the statistical geometry of instantaneous passive scalar and enstrophy fields in turbulence obtained by Bermejo-Moreno & Pullin (2008) and Bermejo-Moreno et al. (J. Fluid Mech., vol. 620, 2009, p. 121), Lagrangian structures tend to exhibit more prevalent sheet-like shapes at intermediate and small scales. For the frozen flow, the Lagrangian field appears to be attracted onto a stream-surface field and it develops less complex multi-scale geometry than found for the turbulent velocity field. In the latter case, there appears to be a tendency for the Lagrangian field to move towards a vortex-surface field of the evolving turbulent flow but this is mitigated by cumulative viscous effects.", "date": "2010-07-10", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "654", "publisher": "Cambridge University Press", "pagerange": "233-270", "id_number": "CaltechAUTHORS:20100805-083626186", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100805-083626186", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF", "grant_number": "DMS-0714050" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/S0022112010000571", "primary_object": { "basename": "Yang2010p10836J_Fluid_Mech.pdf", "url": "https://authors.library.caltech.edu/records/hz9g1-h9097/files/Yang2010p10836J_Fluid_Mech.pdf" }, "resource_type": "article", "pub_year": "2010", "author_list": "Yang, Yue; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/txm47-mvh97", "eprint_id": 18874, "eprint_status": "archive", "datestamp": "2023-08-19 02:49:22", "lastmod": "2023-10-20 19:09:01", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "L\u00f3pez-Ortega-A", "name": { "family": "L\u00f3pez Ortega", "given": "A." } }, { "id": "Hill-D-J", "name": { "family": "Hill", "given": "D. J." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Meiron-D-I", "name": { "family": "Meiron", "given": "D. I." }, "orcid": "0000-0003-0397-3775" } ] }, "title": "Linearized Richtmyer-Meshkov flow analysis for impulsively accelerated incompressible solids", "ispublished": "pub", "full_text_status": "public", "note": "\u00a9 2010 The American Physical Society. \n\nReceived 10 March 2010; published 11 June 2010. \n\nWe want to acknowledge M. Lombardini for his valuable comments on this paper. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award No. DE-FC52-08NA28613.\n\nPublished - Ortega2010p10523Phys_Rev_E.pdf
", "abstract": "We present an analytical study of the linearized impulsive Richtmyer-Meshkov flow for incompressible elastic solids. Seminumerical prior investigations of a related shock-driven compressible elastic problem suggest that the interface amplitude remains bounded in time, in contrast to the unstable behavior found for gases. Our approach considers a base unperturbed flow and a linearization of the conservation equations around the base solution. The resulting initial and boundary value problem is solved using Laplace transform techniques. Analysis of the singularities of the resultant function in the Laplace domain allows us to perform a parametric study of the behavior of the interface in time. We identify two differentiated long-term patterns for the interface, which depends on the material properties: standing wave and oscillating decay. Finally, we present results for the vorticity distribution, which show that the shear stiffness of the solids is responsible both for the stabilization of the interface, and also for the period of the interface oscillations. Comparisons with previous results are discussed.", "date": "2010-06-11", "date_type": "published", "publication": "Physical Review E", "volume": "81", "number": "6", "publisher": "American Physical Society", "pagerange": "Art. No. 066305", "id_number": "CaltechAUTHORS:20100630-133121655", "issn": "1539-3755", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100630-133121655", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Department of Energy (DOE) National Nuclear Security Administration", "grant_number": "DE-FC52-08NA28613" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1103/PhysRevE.81.066305", "primary_object": { "basename": "Ortega2010p10523Phys_Rev_E.pdf", "url": "https://authors.library.caltech.edu/records/txm47-mvh97/files/Ortega2010p10523Phys_Rev_E.pdf" }, "resource_type": "article", "pub_year": "2010", "author_list": "L\u00f3pez Ortega, A.; Hill, D. J.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/65bgr-6rt43", "eprint_id": 17940, "eprint_status": "archive", "datestamp": "2023-08-21 23:46:37", "lastmod": "2023-10-20 15:26:56", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Ward-G-M", "name": { "family": "Ward", "given": "G. M." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "A hybrid, center-difference, limiter method for simulations of compressible multicomponent flows with Mie-Gr\u00fcneisen equation of state", "ispublished": "pub", "full_text_status": "restricted", "keywords": "Hybrid methods; Center difference; Limiter methods; Weighted essentially non-oscillatory methods; Mie-Gr\u00fcneisen equation of state", "note": "\u00a9 2010 Elsevier. \n\nReceived 29 July 2009; revised 9 November 2009; accepted 21 December 2009. Available online 4 January 2010. \n\nThis Material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-FC52-08NA28613.", "abstract": "We develop an efficient spatially high-order, Cartesian-mesh, hybrid, center-difference, limiter methodology for numerical simulations of compressible multicomponent flows with isotropic Mie-Gr\u00fcneisen equation of state. Effective switching between center-difference and limiter schemes is achieved by a set of robust tolerance and Lax-entropy based criterion [18]. Oscillations that could result from a mixed stencil scheme are minimized by requiring that the limiter method approaches the center-difference method in smooth regions. To achieve this the limiter is based on a norm of the deviation of WENO reconstruction weights from ideal. Results from a spatially 4th order version of the methodology are presented in one and two dimensions utilizing the California Institute of Technology's VTF (Virtual Test Facility) AMROC [7] software.", "date": "2010-04-20", "date_type": "published", "publication": "Journal of Computational Physics", "volume": "229", "number": "8", "publisher": "Elsevier", "pagerange": "2999-3018", "id_number": "CaltechAUTHORS:20100412-111520708", "issn": "0021-9991", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100412-111520708", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Department of Energy (DOE) National Nuclear Security Administration", "grant_number": "DE-FC52-08NA28613" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1016/j.jcp.2009.12.027", "resource_type": "article", "pub_year": "2010", "author_list": "Ward, G. M. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/qp5mb-02g61", "eprint_id": 17646, "eprint_status": "archive", "datestamp": "2023-08-21 23:13:28", "lastmod": "2023-10-20 00:06:15", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Kramer-R-M-J", "name": { "family": "Kramer", "given": "R. M. J." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Meiron-D-I", "name": { "family": "Meiron", "given": "D. I." }, "orcid": "0000-0003-0397-3775" }, { "id": "Pantano-C", "name": { "family": "Pantano", "given": "C." } } ] }, "title": "Shock-resolved Navier\u2013Stokes simulation of the Richtmyer\u2013Meshkov instability start-up at a light\u2013heavy interface", "ispublished": "pub", "full_text_status": "public", "keywords": "Computational methods; nonlinear; shock waves", "note": "\u00a9 2009 Cambridge University Press. \n\nReceived 22 April 2009; revised 28 August 2009; accepted 29 August 2009; first published online 9 December 2009. \n\nThis work was supported by the ASC programme of the Department of Energy under subcontract number B341492 of DOE contract W-7405-ENG-48. The authors would like to thank Gustavo Wouchuk for his valuable assistance for providing details of his model.\n\nPublished - Kramer2010p7178J_Fluid_Mech.pdf
", "abstract": "The single-mode Richtmyer\u2013Meshkov instability is investigated using a first-order perturbation of the two-dimensional Navier\u2013Stokes equations about a one-dimensional unsteady shock-resolved base flow. A feature-tracking local refinement scheme is used to fully resolve the viscous internal structure of the shock. This method captures perturbations on the shocks and their influence on the interface growth throughout the simulation, to accurately examine the start-up and early linear growth phases of the instability. Results are compared to analytic models of the instability, showing some agreement with predicted asymptotic growth rates towards the inviscid limit, but significant discrepancies are noted in the transient growth phase. Viscous effects are found to be inadequately predicted by existing models.", "date": "2010-01-10", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "642", "publisher": "Cambridge University Press", "pagerange": "421-443", "id_number": "CaltechAUTHORS:20100303-105410153", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100303-105410153", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Department of Energy (DOE)", "grant_number": "B341492" }, { "agency": "Department of Energy (DOE)", "grant_number": "W-7405-ENG-48" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/S0022112009991911", "primary_object": { "basename": "Kramer2010p7178J_Fluid_Mech.pdf", "url": "https://authors.library.caltech.edu/records/qp5mb-02g61/files/Kramer2010p7178J_Fluid_Mech.pdf" }, "resource_type": "article", "pub_year": "2010", "author_list": "Kramer, R. M. J.; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/m5cdp-p0t72", "eprint_id": 17623, "eprint_status": "archive", "datestamp": "2023-08-19 00:57:00", "lastmod": "2023-10-20 00:04:38", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Chung-Daniel", "name": { "family": "Chung", "given": "D." }, "orcid": "0000-0003-3732-364X" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Direct numerical simulation and large-eddy simulation of stationary buoyancy-driven turbulence", "ispublished": "pub", "full_text_status": "public", "keywords": "modelling, simulation, turbulent mixing", "note": "\u00a9 2009 Cambridge University Press. \n\nReceived 10 June 2009; revised 15 October 2009; accepted 16 October 2009; first published online 24 December 2009. \n\nThe authors wish to thank Drs.W. H. Cabot and A.W. Cook for kindly providing their DNS spectra. This work is partially supported by the \nNSF under grant CBET 0651754.\n\nPublished - Chung2010p7185J_Fluid_Mech.pdf
", "abstract": "We report direct numerical simulation (DNS) and large-eddy simulation (LES) of\nstatistically stationary buoyancy-driven turbulent mixing of an active scalar. We use\nan adaptation of the fringe-region technique, which continually supplies the flow with\nunmixed fluids at two opposite faces of a triply periodic domain in the presence\nof gravity, effectively maintaining an unstably stratified, but statistically stationary\nflow. We also develop a new method to solve the governing equations, based on\nthe Helmholtz\u2013Hodge decomposition, that guarantees discrete mass conservation\nregardless of iteration errors. Whilst some statistics were found to be sensitive to the\ncomputational box size, we show, from inner-scaled planar spectra, that the small\nscales exhibit similarity independent of Reynolds number, density ratio and aspect\nratio. We also perform LES of the present flow using the stretched-vortex subgridscale\n(SGS) model. The utility of an SGS scalar flux closure for passive scalars is\ndemonstrated in the present active-scalar, stably stratified flow setting. The multi-scale\ncharacter of the stretched-vortex SGS model is shown to enable extension of some\nsecond-order statistics to subgrid scales. Comparisons with DNS velocity spectra\nand velocity-density cospectra show that both the resolved-scale and SGS-extended\ncomponents of the LES spectra accurately capture important features of the DNS\nspectra, including small-scale anisotropy and the shape of the viscous roll-off.", "date": "2010", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "643", "publisher": "Cambridge", "pagerange": "279-308", "id_number": "CaltechAUTHORS:20100301-154739581", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100301-154739581", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF", "grant_number": "CBET-0651754" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/S0022112009992801", "primary_object": { "basename": "Chung2010p7185J_Fluid_Mech.pdf", "url": "https://authors.library.caltech.edu/records/m5cdp-p0t72/files/Chung2010p7185J_Fluid_Mech.pdf" }, "resource_type": "article", "pub_year": "2010", "author_list": "Chung, D. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/nwytb-r2s87", "eprint_id": 17246, "eprint_status": "archive", "datestamp": "2023-08-19 00:28:49", "lastmod": "2023-10-19 23:41:29", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Lombardini-M", "name": { "family": "Lombardini", "given": "M." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Small-amplitude perturbations in the three-dimensional cylindrical Richtmyer\u2013Meshkov instability", "ispublished": "pub", "full_text_status": "public", "keywords": "flow instability, shock waves", "note": "\u00a9 2009 American Institute of Physics.\nReceived 13 May 2009; accepted 8 September 2009; published 6 November 2009.\nThis work was supported by the Advanced Simulation\nand Computing (ASC) Program under Subcontract No.\nB341492 of DOE (Contract No. W-7405-ENG-48).\n\nPublished - Lombardini2009p6690Phys_Fluids.pdf
", "abstract": "We first study the linear stability of an interface between two fluids following the passage of an imploding or exploding shock wave. Assuming incompressible flow between the refracted waves following shock impact, we derive an expression for the asymptotic growth rate for a three-dimensional combination of azimuthal and axial perturbations as a function of the Atwood ratio, the axial and azimuthal wave numbers, the initial radial position and perturbation amplitude of the interface, and the interface velocity gain due to the shock interaction. From the linearized theory, a unified expression for the impulsive asymptotic growth rate in plane, cylindrical, and spherical geometries is obtained which clearly delineates the effects of perturbation growth due to both geometry and baroclinic vorticity deposition. Several different limit cases are investigated, allowing recovery of Mikaelian's purely azimuthal theory and Richtmyer's plane model. We discuss the existence of three-dimensional perturbations with zero growth, typical of curvilinear geometries, as first observed by Mikaelian. The effect of shock proximity on the interface growth rate is studied in the case of a reflected shock. Analytical predictions of the effect of the incident shock strength and the perturbation wave numbers are then compared with results obtained from highly resolved numerical simulations of cylindrical imploding Richtmyer\u2013Meshkov instability for ideal gases. A parallel is made with the instability growth in spherical and plane geometry. In particular, we propose a representation of the perturbation growth by considering the volume of the perturbed layer. This volume is found to grow faster in the plane case than in the imploding cylindrical geometry, among other results.", "date": "2009-11", "date_type": "published", "publication": "Physics of Fluids", "volume": "21", "number": "11", "publisher": "American Institute of Physics", "pagerange": "Art. No. 114103", "id_number": "CaltechAUTHORS:20100120-131115012", "issn": "1070-6631", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100120-131115012", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Department of Energy", "grant_number": "B341492" }, { "agency": "Department of Energy", "grant_number": "W-7405-ENG-48" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.3258668", "primary_object": { "basename": "Lombardini2009p6690Phys_Fluids.pdf", "url": "https://authors.library.caltech.edu/records/nwytb-r2s87/files/Lombardini2009p6690Phys_Fluids.pdf" }, "resource_type": "article", "pub_year": "2009", "author_list": "Lombardini, M. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/26f2w-hvs80", "eprint_id": 16383, "eprint_status": "archive", "datestamp": "2023-08-21 22:07:44", "lastmod": "2023-10-19 22:10:25", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Wheatley-V", "name": { "family": "Wheatley", "given": "V." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "The Richtmyer\u2013Meshkov instability in magnetohydrodynamics", "ispublished": "pub", "full_text_status": "public", "keywords": "compressible flow; flow instability; flow simulation; magnetohydrodynamics; shock waves.", "note": "\u00a9 2009 American Institute of Physics.\n\nReceived 8 February 2009; accepted 23 June 2009; published 25 August 2009.\n\nV. Wheatley and D. I. Pullin were supported by the Academic\nStrategic Alliances Program of the Accelerated Strategic\nComputing Initiative ASCI/ASAP under Subcontract\nNo. B341492 of DOE Contract No. W-7405-ENG-48. R.\nSamtaney was supported by U.S. DOE Contract No. DEAC02-\n09CH11466.\n\nPublished - Wheatley2009p6081Phys_Fluids.pdf
", "abstract": "In ideal magnetohydrodynamics (MHD), the Richtmyer\u2013Meshkov instability can be suppressed by the presence of a magnetic field. The interface still undergoes some growth, but this is bounded for a finite magnetic field. A model for this flow has been developed by considering the stability of an impulsively accelerated, sinusoidally perturbed density interface in the presence of a magnetic field that is parallel to the acceleration. This was accomplished by analytically solving the linearized initial value problem in the framework of ideal incompressible MHD. To assess the performance of the model, its predictions are compared to results obtained from numerical simulation of impulse driven linearized, shock driven linearized, and nonlinear compressible MHD for a variety of cases. It is shown that the analytical linear model collapses the data from the simulations well. The predicted interface behavior well approximates that seen in compressible linearized simulations when the shock strength, magnetic field strength, and perturbation amplitude are small. For such cases, the agreement with interface behavior that occurs in nonlinear simulations is also reasonable. The effects of increasing shock strength, magnetic field strength, and perturbation amplitude on both the flow and the performance of the model are investigated. This results in a detailed exposition of the features and behavior of the MHD Richtmyer\u2013Meshkov flow. For strong shocks, large initial perturbation amplitudes, and strong magnetic fields, the linear model may give a rough estimate of the interface behavior, but it is not quantitatively accurate. In all cases examined the accuracy of the model is quantified and the flow physics underlying any discrepancies is examined", "date": "2009-08-25", "date_type": "published", "publication": "Physics of Fluids", "volume": "21", "number": "8", "publisher": "American Institute of Physics", "pagerange": "082102", "id_number": "CaltechAUTHORS:20091019-120155094", "issn": "1070-6631", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20091019-120155094", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Academic Strategic Alliance Program, Accelerated Strategic Computing Initiative (ASCI/ASAP)", "grant_number": "B341492" }, { "agency": "U. S. Department of Energy", "grant_number": "W-7405-ENG-48" }, { "agency": "U. S. Department of Energy", "grant_number": "DE-AC02-09CH11466" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.3194303", "primary_object": { "basename": "Wheatley2009p6081Phys_Fluids.pdf", "url": "https://authors.library.caltech.edu/records/26f2w-hvs80/files/Wheatley2009p6081Phys_Fluids.pdf" }, "resource_type": "article", "pub_year": "2009", "author_list": "Wheatley, V. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/1n4g7-8hj34", "eprint_id": 15608, "eprint_status": "archive", "datestamp": "2023-08-21 22:00:19", "lastmod": "2023-10-19 14:37:57", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Kramer-R-M-J", "name": { "family": "Kramer", "given": "R. M. J." } }, { "id": "Pantano-C", "name": { "family": "Pantano", "given": "C." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Nondissipative and energy-stable high-order finite-difference interface schemes for 2-D patch-refined grids", "ispublished": "pub", "full_text_status": "restricted", "keywords": "High-order finite difference; Mesh interface; Stable stencil; Adaptive mesh refinement; Summation by parts", "note": "Copyright \u00a9 2009 Elsevier. \n\nReceived 27 May 2008; revised 3 April 2009; accepted 8 April 2009. Available online 22 April 2009. \n\nThis work was supported by the ASC program of the Department of Energy under Subcontract No. B341492 of DOE Contract W-7405-ENG-48. The authors would like to thank the reviewers for valuable and constructive comments, in particular for requesting clarifications with respect to discrete conservation. \n\nSupplementary data associated with this article can be found, in the online version, at doi:10.1016/j.jcp.2009.04.010.", "abstract": "A class of finite-difference interface schemes suitable for two-dimensional cell-centered grids with patch-refinement and step-changes in resolution is presented. Grids of this type are generated by adaptive mesh refinement methods according to resolution needs dictated by the physics of the problem being modeled. For these grids, coarse and fine nodes are not aligned at the mesh interfaces, resulting in hanging nodes. Three distinct geometries are identified at the interfaces of a domain with interior patch-refinement: edges, concave corners and convex corners. Asymptotic stability in time of the numerical scheme is achieved by imposing a summation-by-parts condition on the interface closure, which is thus also nondissipative. Interface stencils corresponding to an explicit fourth-order finite-difference scheme are presented for each geometry. To preserve stability, a reduction in local accuracy is required at the corner geometries. It is also found that no second-order accurate solution exists that satisfies the summation-by-parts condition. Tests using the 2-D scalar advection equation and an inviscid compressible vortex support the stability and accuracy of these stencils for both linear and nonlinear problems.", "date": "2009-08-01", "date_type": "published", "publication": "Journal of Computational Physics", "volume": "228", "number": "14", "publisher": "Elsevier", "pagerange": "5280-5297", "id_number": "CaltechAUTHORS:20090904-101804788", "issn": "0021-9991", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090904-101804788", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Department of Energy", "grant_number": "W-7405-ENG-48" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1016/j.jcp.2009.04.010", "resource_type": "article", "pub_year": "2009", "author_list": "Kramer, R. M. J.; Pantano, C.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/wdpae-kd094", "eprint_id": 15454, "eprint_status": "archive", "datestamp": "2023-08-20 02:21:04", "lastmod": "2023-10-18 21:48:31", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Chung-Daniel", "name": { "family": "Chung", "given": "D." }, "orcid": "0000-0003-3732-364X" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Large-eddy simulation and wall modelling of turbulent channel flow", "ispublished": "pub", "full_text_status": "public", "note": "\u00a9 Cambridge University Press 2009. \n\n(Received 28 May 2008 and in revised form 8 March 2009). Published online by Cambridge University Press 17 July 2009. \n\nThe authors wish to thank Professor J. Jim\u00e9nez who kindly provided DNS spectra. This work is partially supported by the NSF under grant CBET 0651754.\n\nPublished - Chung2009p5777J_Fluid_Mech.pdf
", "abstract": "We report large-eddy simulation (LES) of turbulent channel flow. This LES neither resolves nor partially resolves the near-wall region. Instead, we develop a special near-wall subgrid-scale (SGS) model based on wall-parallel filtering and wall-normal averaging of the streamwise momentum equation, with an assumption of local inner scaling used to reduce the unsteady term. This gives an ordinary differential equation (ODE) for the wall shear stress at every wall location that is coupled with the LES. An extended form of the stretched-vortex SGS model, which incorporates the production of near-wall Reynolds shear stress due to the winding of streamwise momentum by near-wall attached SGS vortices, then provides a log relation for the streamwise velocity at the top boundary of the near-wall averaged domain. This allows calculation of an instantaneous slip velocity that is then used as a 'virtual-wall' boundary condition for the LES. A K\u00e1rm\u00e1n-like constant is calculated dynamically as part of the LES. With this closure we perform LES of turbulent channel flow for Reynolds numbers Re_\u03c4 based on the friction velocity u_\u03c4 and the channel half-width \u03b4 in the range 2 \u00d7 10^3 to 2 \u00d7 10^7. Results, including SGS-extended longitudinal spectra, compare favourably with the direct numerical simulation (DNS) data of Hoyas & Jim\u00e9nez (2006) at Re_\u03c4 = 2003 and maintain an O(1) grid dependence on Re_\u03c4.", "date": "2009-07-25", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "631", "publisher": "Cambridge University Press", "pagerange": "281-309", "id_number": "CaltechAUTHORS:20090828-231034531", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090828-231034531", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF", "grant_number": "CBET-0651754" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/S0022112009006867", "primary_object": { "basename": "Chung2009p5777J_Fluid_Mech.pdf", "url": "https://authors.library.caltech.edu/records/wdpae-kd094/files/Chung2009p5777J_Fluid_Mech.pdf" }, "resource_type": "article", "pub_year": "2009", "author_list": "Chung, D. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/3zrxp-qme10", "eprint_id": 15180, "eprint_status": "archive", "datestamp": "2023-08-21 21:08:22", "lastmod": "2023-10-18 21:03:24", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Lombardini-M", "name": { "family": "Lombardini", "given": "M." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Startup process in the Richtmyer-Meshkov instability", "ispublished": "pub", "full_text_status": "public", "keywords": "flow instability; flow simulation; interface phenomena; perturbation theory; shock wave effects; shock waves", "note": "\u00a9 2009 American Institute of Physics.\nReceived 2 October 2008; accepted 4 November 2008; published 14 April 2009.\nThis work was supported by the Advanced Simulation\nand Computing ASC Program under Subcontract No.\nB341492 of DOE Contract No. W-7405-ENG-48. M.L. and\nD.I.P. would like to thank Dr. David J. Hill for numerous\ndiscussions and comments on the manuscript.\n\nPublished - Lombardini2009p4555Phys_Fluids.pdf
", "abstract": "An analytical model for the initial growth period of the planar Richtmyer\u2013Meshkov instability is presented for the case of a reflected shock, which corresponds in general to light-to-heavy interactions. The model captures the main features of the interfacial perturbation growth before the regime with linear growth in time is attained. The analysis provides a characteristic time scale \u03c4 for the startup phase of the instability, expressed explicitly as a function of the perturbation wavenumber k, the algebraic transmitted and reflected shock speeds U_(S1) < 0 and U_(S2) > 0 (defined in the frame of the accelerated interface), and the postshock Atwood number A^+: \u03c4=[(1-A^+)/U_(S2)+(1+A^+)/(-U_(s1))]/(2k). Results are compared with computations obtained from two-dimensional highly resolved numerical simulations over a wide range of incident shock strengths S and preshock Atwood ratios A. An interesting observation shows that, within this model, the amplitude of small perturbations across a light-to-heavy interface evolves quadratically in time (and not linearly) in the limit A\u21921^\u2212.", "date": "2009-04", "date_type": "published", "publication": "Physics of Fluids", "volume": "21", "number": "4", "publisher": "American Institute of Physics", "pagerange": "044104", "id_number": "CaltechAUTHORS:20090820-090629481", "issn": "1070-6631", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090820-090629481", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Department of Energy", "grant_number": "B341492" }, { "agency": "Department of Energy", "grant_number": "W-7405-ENG-48" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.3091943", "primary_object": { "basename": "Lombardini2009p4555Phys_Fluids.pdf", "url": "https://authors.library.caltech.edu/records/3zrxp-qme10/files/Lombardini2009p4555Phys_Fluids.pdf" }, "resource_type": "article", "pub_year": "2009", "author_list": "Lombardini, M. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/t7qsn-n8t38", "eprint_id": 14361, "eprint_status": "archive", "datestamp": "2023-08-20 00:46:50", "lastmod": "2023-10-18 16:48:31", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Bermejo-Moreno-I", "name": { "family": "Bermejo-Moreno", "given": "Iv\u00e1n" } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Horiuti-K", "name": { "family": "Horiuti", "given": "Kiyoshi" } } ] }, "title": "Geometry of enstrophy and dissipation, grid resolution effects and proximity issues in turbulence", "ispublished": "pub", "full_text_status": "public", "note": "\u00a9 2009 Cambridge University Press. \nReceived 5 June 2008 and in revised form 20 October 2008; published online by Cambridge University Press 26 January 2009.\nThis work has been supported in part by the National Science Foundation under Grant FRG DMS-0353838. K. H. is supported by Grants-in-Aid from the Ministry of Education, Culture, Sports, Science and Technology, Japan (No. 18560156). Part of the computations were performed at Cybermedia Centre, Osaka University and National Institute for Fusion Science.\n\nPublished - BermejoMoreno2009p11110.1017S002211200800476X.pdf
", "abstract": "We perform a multi-scale non-local geometrical analysis of the structures extracted from the enstrophy and kinetic energy dissipation-rate, instantaneous fields of a numerical database of incompressible homogeneous isotropic turbulence decaying in time obtained by DNS in a periodic box. Three different resolutions are considered: 256^3, 512^3 and 1024^3 grid points, with k_(max)\u03b7(overbar) approximately 1, 2 and 4, respectively, the same initial conditions and Re_\u03bb \u2248 77. This allows a comparison of the geometry of the structures obtained for different resolutions. For the highest resolution, structures of enstrophy and dissipation evolve in a continuous distribution from blob-like and moderately stretched tube-like shapes at the large scales to highly stretched sheet-like structures at the small scales. The intermediate scales show a predominance of tube-like structures for both fields, much more pronounced for the enstrophy field. The dissipation field shows a tendency towards structures with lower curvedness than those of the enstrophy, for intermediate and small scales. The 256^3 grid resolution case (k_(max)\u03b7(overbar) \u2248 1) was unable to detect the predominance of highly stretched sheet-like structures at the smaller scales in both fields. The same non-local methodology for the study of the geometry of structures, but without the multi-scale decomposition, is applied to two scalar fields used by existing local criteria for the eduction of tube- and sheet-like structures in turbulence, Q and [A_ij]_+, respectively, obtained from invariants of the velocity-gradient tensor and alike in the 1024^3 case. This adds the non-local geometrical characterization and classification to those local criteria, assessing their validity in educing particular geometries. Finally, we introduce a new methodology for the study of proximity issues among structures of different fields, based on geometrical considerations and non-local analysis, by taking into account the spatial extent of the structures. We apply it to the four fields previously studied. Tube-like structures of Q are predominantly surrounded by sheet-like structures of [A_ij]_+, which appear at closer distances. For the enstrophy, tube-like structures at an intermediate scale are primarily surrounded by sheets of smaller scales of the enstrophy and structures of dissipation at the same and smaller scales. A secondary contribution results from tubes of enstrophy at smaller scales appearing at farther distances. Different configurations of composite structures are presented.", "date": "2009-02", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "620", "publisher": "Cambridge University Press", "pagerange": "121-166", "id_number": "CaltechAUTHORS:20090603-165553557", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090603-165553557", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF", "grant_number": "FRG DMS-0353838" }, { "agency": "Ministry of Education, Culture, Sports, Science and Technology, Japan", "grant_number": "No. 18560156" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/S002211200800476X", "primary_object": { "basename": "BermejoMoreno2009p11110.1017S002211200800476X.pdf", "url": "https://authors.library.caltech.edu/records/t7qsn-n8t38/files/BermejoMoreno2009p11110.1017S002211200800476X.pdf" }, "resource_type": "article", "pub_year": "2009", "author_list": "Bermejo-Moreno, Iv\u00e1n; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/7n6wp-z4n97", "eprint_id": 13964, "eprint_status": "archive", "datestamp": "2023-08-22 14:18:05", "lastmod": "2023-10-18 15:59:59", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Goldsworthy-M-J", "name": { "family": "Goldsworthy", "given": "M. J." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Mean free path effects in the shock-implosion problem", "ispublished": "pub", "full_text_status": "public", "keywords": "explosions; flow simulation; Knudsen flow; Mach number; Monte Carlo methods; shock waves", "note": "\u00a9 2009 American Institute of Physics.\nReceived 24 April 2008; accepted 23 December 2008; published 11 February 2009.\n\nPublished - Goldsworthy2009p52910.10631.3075952.pdf
", "abstract": "The effects of finite Knudsen number in the problem of a cylindrically imploding shock wave in a monatomic gas are investigated. Numerical solutions of the flow field are obtained with initial conditions in the ranges 1.25 \u2264 M0 \u2264 5 and 0.005 \u2264 Kn0 \u2264 0.1 using the direct simulation Monte Carlo method. Results show that as Kn0 decreases and M0 increases, the maximum implosion temperature scales increasingly well with the similarity exponent predicted in the Guderley solution for an imploding strong shock in the Euler limit. When the radius of curvature is large, the cylindrical shock thickness is found to be almost identical to the thickness of a planar shock for a given shock Mach number. For small radii of curvature, the cylindrical shock was found to be thicker than the corresponding planar shock.", "date": "2009-02", "date_type": "published", "publication": "Physics of Fluids", "volume": "21", "number": "2", "publisher": "American Institute of Physics", "pagerange": "026101", "id_number": "CaltechAUTHORS:20090414-090059769", "issn": "1070-6631", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090414-090059769", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.3075952", "primary_object": { "basename": "Goldsworthy2009p52910.10631.3075952.pdf", "url": "https://authors.library.caltech.edu/records/7n6wp-z4n97/files/Goldsworthy2009p52910.10631.3075952.pdf" }, "resource_type": "article", "pub_year": "2009", "author_list": "Goldsworthy, M. J. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/89axv-7am59", "eprint_id": 13287, "eprint_status": "archive", "datestamp": "2023-08-20 00:04:07", "lastmod": "2023-10-17 23:23:10", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Hornung-H-G", "name": { "family": "Hornung", "given": "H. G." }, "orcid": "0000-0002-4903-8419" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Ponchaut-N-F", "name": { "family": "Ponchaut", "given": "N. F." } } ] }, "title": "On the question of universality of imploding shock waves", "ispublished": "pub", "full_text_status": "restricted", "note": "\u00a9 Springer-Verlag 2008. \n\nReceived: 9 March 2008. Revised: 27 March 2008. Published online: 5 August 2008. \n\nAlthough Professor Schneider's extensive contributions include elements of experimental work, he is himself primarily an inspiring theoretical fluid mechanicist, from whom we have learned a lot. It is therefore fitting that we honor him at his anniversary with this theoretical contribution. \n\nDedicated to Professor Wilhelm Schneider on the occasion of his 70th birthday.", "abstract": "For the case of initially infinitesimally weak spherically and cylindrically imploding shocks, Ponchaut et al. (J. Fluid Mech., 560: 102-122, 2006) recently obtained universal solutions. We study the effect of starting the shock with an initially finite strength on the trajectory of the shock by performing numerical calculations for the incoming shock imploding spherically into a diatomic perfect gas. Deviations from the universal solution are extremely small. A solution for the initially infinitesimally weak shock obtained by using Whitham's (Linear and nonlinear waves, Wiley, New York, 1974) Shock Dynamics is virtually indistinguishable from the Ponchaut solution.", "date": "2008-12", "date_type": "published", "publication": "Acta Mechanica", "volume": "201", "number": "1-4", "publisher": "Springer", "pagerange": "31-35", "id_number": "CaltechAUTHORS:HORam08", "issn": "0001-5970", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:HORam08", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1007/s00707-008-0070-2", "resource_type": "article", "pub_year": "2008", "author_list": "Hornung, H. G.; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/f6dyy-bab31", "eprint_id": 13579, "eprint_status": "archive", "datestamp": "2023-08-19 23:55:11", "lastmod": "2023-10-18 00:00:22", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Rosakis-A-J", "name": { "family": "Rosakis", "given": "Ares" }, "orcid": "0000-0003-0559-0794" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "Dale" } } ] }, "title": "Dedication [to Tony Leonard]", "ispublished": "pub", "full_text_status": "restricted", "note": "\u00a9 2008 Elsevier Inc. \nAvailable online 28 August 2008.", "abstract": "Over more than 30 years, Tony Leonard's contributions to fluid mechanics, continuum mechanics and numerical methods have been dense and seminal. He has worked in diverse areas including vortex dynamics, vortex-based numerical methods, wall-bounded turbulence, quantized turbulence, Large\u2013Eddy Simulation (LES), Lagrangian mixing, spectral numerical methods, bluff body flows and flow-induced vibrations. Tony's first paper on LES, \"Energy Cascade in Large\u2013Eddy Simulation of Turbulent Fluid Flows\" appeared as an article in a review series, \"Advances in Geophysics\", in 1974. It proposed the concept of spatial filtering that has since been a cornerstone of LES. The idea of numerically simulating the evolution of large scales of turbulence while modeling the small scales was not new in the 1970s but it lacked a firm theoretical framework for the conceptual separation of the resolved or computed scales, and the subgrid or unresolved scales. Tony Leonard's 1974 introduction of the convolution operation of a field with a filter to produce the resolvable-scale function, and its application to the Navier Stokes equations of motion provided the means of identifying \"resolved scales\" while isolating and grouping those filtered products of subgrid fields with themselves and with resolved-scale fields, that required modeling. Tony's filter formalism has had a profound impact on the development of LES methodology and indeed is the starting point for most modern expositions on this topic. There is little doubt that his 1974 paper, which has not been published elsewhere, has become an unquantified citation classic.", "date": "2008-11-10", "date_type": "published", "publication": "Journal of Computational Physics", "volume": "227", "number": "21", "publisher": "Elsevier", "pagerange": "9006-9007", "id_number": "CaltechAUTHORS:ROSjcp08", "issn": "0021-9991", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:ROSjcp08", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1016/j.jcp.2008.08.006", "resource_type": "article", "pub_year": "2008", "author_list": "Rosakis, Ares and Pullin, Dale" }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/775va-2jy03", "eprint_id": 13409, "eprint_status": "archive", "datestamp": "2023-08-22 13:33:57", "lastmod": "2023-10-17 23:52:32", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pantano-Carlos", "name": { "family": "Pantano", "given": "C." }, "orcid": "0000-0003-3971-2278" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Dimotakis-P-E", "name": { "family": "Dimotakis", "given": "P. E." } }, { "id": "Matheou-Georgios", "name": { "family": "Matheou", "given": "G." }, "orcid": "0000-0003-4024-4571" } ] }, "title": "LES approach for high Reynolds number wall-bounded flows with application to turbulent channel flow", "ispublished": "pub", "full_text_status": "restricted", "keywords": "LES; numerical methods; turbulence modeling; wall functions; law of the wall; boundary conditions", "note": "\u00a9 2008 Elsevier Inc. \n\nReceived 18 April 2007; received in revised form 18 February 2008; accepted 8 April 2008. Available online 26 April 2008. \n\nSpecial Issue Celebrating Tony Leonard's 70th Birthday. \n\nWe acknowledge fruitful discussions with Dr. A. Ferrante and thank the reviewers for many valuable comments. \n\nThis work was largely undertaken while the first author resided at the California Institute of Technology, and was supported by AFOSR Grants FA9550-04-1-0020 and \nFA9550-04-1-0389, and by the Advanced Simulation and Computing (ASC) Program under Subcontract No. B341492 of the Department of Energy Contract W-7405-ENG-48.", "abstract": "We describe a large-eddy simulation approach for turbulent channel flow using the stretched-vortex subgrid-scale model. The inner region of the turbulent boundary layer is not included in the modeling of this attached, wall-bounded flow. Appropriate boundary conditions and closure are derived using a combination of elements from asymptotic expansions, matching, and well-established wall-modeling approaches. The modeling approach for this application combines the stretched-vortex subgrid model with a localized wall-shear-stress treatment that relates the instantaneous wall-parallel velocity to the shear stress via the log-law, as appropriate for this (near-) zero pressure gradient flow. The impermeability boundary condition is built into the method such that only the outer-flow solution is simulated, obviating the need to impose the stiff no-slip condition at the wall. This formulation attempts to minimize numerical and modeling errors introduced by the boundary-condition treatment, while preserving the fundamental elements required to predict low-order statistics of these flows. We present simulation results for turbulent channel flow up to Reynolds number based oil the wall-friction velocity of 10^6. These compare favorably with results from large-scale DNS and experimental correlations.", "date": "2008-11-10", "date_type": "published", "publication": "Journal of Computational Physics", "volume": "227", "number": "21", "publisher": "Elsevier", "pagerange": "9271-9291", "id_number": "CaltechAUTHORS:PANjcp08", "issn": "0021-9991", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:PANjcp08", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Air Force Office of Scientific Research (AFOSR)", "grant_number": "FA9550-04-1-0020" }, { "agency": "Air Force Office of Scientific Research (AFOSR)", "grant_number": "FA9550-04-1-0389" }, { "agency": "Department of Energy (DOE)", "grant_number": "B341492" }, { "agency": "Department of Energy (DOE)", "grant_number": "W-7405-ENG-48" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1016/j.jcp.2008.04.015", "resource_type": "article", "pub_year": "2008", "author_list": "Pantano, C.; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/qt1y3-x3m43", "eprint_id": 98525, "eprint_status": "archive", "datestamp": "2023-08-22 12:46:23", "lastmod": "2024-01-14 21:56:08", "type": "book_section", "metadata_visibility": "show", "creators": { "items": [ { "id": "Lombardini-M", "name": { "family": "Lombardini", "given": "Manuel" } }, { "id": "Deiterding-R", "name": { "family": "Deiterding", "given": "Ralf" } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Large Eddy Simulations of the Richtmyer\u2013Meshkov Instability in a Converging Geometry", "ispublished": "unpub", "full_text_status": "restricted", "keywords": "Large-eddy simulations (LES) with strong shocks; Richtmyer-Meshkov instability (RMI); Compressible turbulent mixing; Adaptive mesh refinement (AMR)", "note": "\u00a9 Springer-Verlag Berlin Heidelberg 2008. \n\nThe authors would like to acknowledge the helpful conversations with D.J. Hill. This work is supported by the ASC program of the Department of Energy under subcontract no. B341492 of DoE contract W-7405-ENG-48.", "abstract": "This work presents on-going research on large-eddy simulations of shock-generated mixing in Richtmyer-Meshkov flow in converging geometries. A hybrid numerical method is used on each subgrid of the mesh hierarchy within the AMROC (adaptive mesh refinement object oriented C++) framework: it is a shock capturing method but reverts to a centered scheme with low numerical viscosity in regions of smoother flow. The stretched-vortex subgrid-scale model allows for the capturing of the small-scale mixing process between the two fluids. Results presented focus on the evolution of the mixing layer and its internal statistics including various spectra and p.d.f.s of mixed molar and mass fractions. A detailed quantitative analysis has also been conducted including space-time histories of instantaneous cylindrical shell-averages of diverse quantities, taken concentrically to the main shocks. Comparisons are made with the planar Richtmyer-Meshkov instability with reshock studied by Vetter and Sturtevant (1995) [1] and Hill et al. (2006).", "date": "2008-08-20", "date_type": "published", "publisher": "Springer Netherlands", "place_of_pub": "Dordrecht", "pagerange": "283-294", "id_number": "CaltechAUTHORS:20190909-133031443", "isbn": "9781402085772", "book_title": "Quality and Reliability of Large-Eddy Simulations", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190909-133031443", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Department of Energy (DOE)", "grant_number": "W-7405-ENG-48" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "contributors": { "items": [ { "id": "Meyers-J", "name": { "family": "Meyers", "given": "Johan" } }, { "id": "Geurtz-B-J", "name": { "family": "Geurts", "given": "Bernard J." } }, { "id": "Sagaut-P", "name": { "family": "Sagaut", "given": "Pierre" } } ] }, "doi": "10.1007/978-1-4020-8578-9_23", "resource_type": "book_section", "pub_year": "2008", "author_list": "Lombardini, Manuel; Deiterding, Ralf; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/yv3kv-0zq93", "eprint_id": 10428, "eprint_status": "archive", "datestamp": "2023-08-22 11:41:13", "lastmod": "2023-10-16 22:51:43", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Bermejo-Moreno-I", "name": { "family": "Bermejo-Moreno", "given": "Iv\u00e1n" } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "On the non-local geometry of turbulence", "ispublished": "pub", "full_text_status": "public", "note": "Copyright \u00a9 Cambridge University Press 2008. Reprinted with permission. \n\n(Received 12 July 2007 and in revised form 26 January 2008) \n\nThe authors are grateful to P. O'Gorman for providing the numerical turbulence database, and to E. Cand\u00e8s and L. Ying for valuable discussions regarding the curvelet transform and for providing, along with L. Demanet, the Curvelab software on which our implementation of the multi-scale filtering in curvelet space is based. This work has been supported in part by the National Science Foundation under Grant DMS-0353838 and DMS-0714050.", "abstract": "A multi-scale methodology for the study of the non-local geometry of eddy structures in turbulence is developed. Starting from a given three-dimensional field, this consists of three main steps: extraction, characterization and classification of structures. The extraction step is done in two stages. First, a multi-scale decomposition based on the curvelet transform is applied to the full three-dimensional field, resulting in a finite set of component three-dimensional fields, one per scale. Second, by iso-contouring each component field at one or more iso-contour levels, a set of closed iso-surfaces is obtained that represents the structures at that scale. The characterization stage is based on the joint probability density function (p.d.f.), in terms of area coverage on each individual iso-surface, of two differential-geometry properties, the shape index and curvedness, plus the stretching parameter, a dimensionless global invariant of the surface. Taken together, this defines the geometrical signature of the iso-surface. The classification step is based on the construction of a finite set of parameters, obtained from algebraic functions of moments of the joint p.d.f. of each structure, that specify its location as a point in a multi-dimensional 'feature space'. At each scale the set of points in feature space represents all structures at that scale, for the specified iso-contour value. This then allows the application, to the set, of clustering techniques that search for groups of structures with a common geometry. Results are presented of a first application of this technique to a passive scalar field obtained from 5123 direct numerical simulation of scalar mixing by forced, isotropic turbulence (Re\u03bb = 265). These show transition, with decreasing scale, from blob-like structures in the larger scales to blob- and tube-like structures with small or moderate stretching in the inertial range of scales, and then toward tube and, predominantly, sheet-like structures with high level of stretching in the dissipation range of scales. Implications of these results for the dynamical behaviour of passive scalar stirring and mixing by turbulence are discussed.", "date": "2008-05-01", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "603", "publisher": "Journal of Fluid Mechanics", "pagerange": "101-135", "id_number": "CaltechAUTHORS:BERjfm08", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:BERjfm08", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/S002211200800092X", "primary_object": { "basename": "BERjfm08.pdf", "url": "https://authors.library.caltech.edu/records/yv3kv-0zq93/files/BERjfm08.pdf" }, "resource_type": "article", "pub_year": "2008", "author_list": "Bermejo-Moreno, Iv\u00e1n and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/x8p9d-qky48", "eprint_id": 19981, "eprint_status": "archive", "datestamp": "2023-08-19 19:11:13", "lastmod": "2024-01-13 00:01:48", "type": "book_section", "metadata_visibility": "show", "creators": { "items": [ { "id": "Hill-D-J", "name": { "family": "Hill", "given": "D. J." } }, { "id": "Pantano-C", "name": { "family": "Pantano", "given": "C." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Large-Eddy Simulation of Richtmyer-Meshkov Instability", "ispublished": "unpub", "full_text_status": "restricted", "note": "\u00a9 2007 Springer.\n\nThis work was supported by the Advanced Simulation and Computing (ASC) Program under subcontract no. B341492 of DOE contract W-7405-ENG-48. The authors would like to acknowledge the many helpful conversations with P.E. Dimotakis and D.I. Meiron.", "abstract": "We present results from large-eddy simulations (LES) of three-dimensional Richtmyer-Meshkov (RM) instability in a rectangular tube with reshock off the tube endwall. A hybrid numerical method is used that is shock capturing but\nwhich reverts to a centered scheme with low numerical viscosity in regions of smooth flow. The subgrid-scale (SGS) model is the stretched-vortex (SV) model [1]. The\nshock strength, tube geometry, gas composition, initial conditions and initial interface disturbance were tailored to the experimental conditions of Vetter & Sturtevant\n[2] with shock Mach number M_s = 1.5, density ratio r = 5, and constituent gases air and SF_6. Use of the SV SGS model allows continuation of radial velocity spectra in the center-plane of the mixing layer, to subgrid scales, including the effect of anisotropy and self-consistent calculation of the viscous cutoff scale.", "date": "2007", "date_type": "published", "publisher": "Springer", "pagerange": "263-271", "id_number": "CaltechAUTHORS:20100916-112754310", "isbn": "978-3-540-34233-5", "book_title": "Complex Effects in Large Eddy Simulations", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100916-112754310", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Advanced Simulation and Computing (ASC) Program, DOE", "grant_number": "B341492" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "contributors": { "items": [ { "id": "Kassinos-S", "name": { "family": "Kassinos", "given": "Stavros" } }, { "id": "Langer-C-A", "name": { "family": "Langer", "given": "Carlos A." } }, { "id": "Iaccarino-G", "name": { "family": "Iaccarino", "given": "Gianluca" } }, { "id": "Moin-Parviz", "name": { "family": "Moin", "given": "Parviz" } } ] }, "doi": "10.1007/978-3-540-34234-2_19", "resource_type": "book_section", "pub_year": "2007", "author_list": "Hill, D. J.; Pantano, C.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/3zghb-r4x40", "eprint_id": 4820, "eprint_status": "archive", "datestamp": "2023-08-22 06:18:21", "lastmod": "2023-10-16 17:57:19", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Ponchaut-N-F", "name": { "family": "Ponchaut", "given": "N. F." } }, { "id": "Hornung-H-G", "name": { "family": "Hornung", "given": "H. G." }, "orcid": "0000-0002-4903-8419" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Mouton-C-A", "name": { "family": "Mouton", "given": "C. A." } } ] }, "title": "On imploding cylindrical and spherical shock waves in a perfect gas", "ispublished": "pub", "full_text_status": "public", "note": "Copyright \u00a9 2006 Cambridge University Press. Reprinted with permission. \n\n(Received 4 July 2005 and in revised form 6 January 2006) Published online 20 July 2006 \n\nN.P. and D.P. were partially supported by the Academic Strategic Alliances Program of the Accelerated Strategic Computing Initiative (ASCI/ASAP) under subcontract no. B341492 of DOE contract W-7405-ENG-48.", "abstract": "The problem of a cylindrically or spherically imploding and reflecting shock wave in a flow initially at rest is studied without the use of the strong-shock approximation. Dimensional arguments are first used to show that this flow admits a general solution where an infinitesimally weak shock from infinity strengthens as it converges towards the origin. For a perfect-gas equation of state, this solution depends only on the dimensionality of the flow and on the ratio of specific heats. The Guderley power-law result can then be interpreted as the leading-order, strong-shock approximation, valid near the origin at the implosion centre. We improve the Guderley solution by adding two further terms in the series expansion solution for both the incoming and the reflected shock waves. A series expansion, valid where the shock is still weak and very far from the origin, is also constructed. With an appropriate change of variables and using the exact shock-jump conditions, a numerical, characteristics-based solution is obtained describing the general shock motion from almost infinity to very close to the reflection point. Comparisons are made between the series expansions, the characteristics solution, and the results obtained using an Euler solver. These show that the addition of two terms to the Guderley solution significantly extends the range of validity of the strong-shock series expansion.", "date": "2006-08-10", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "560", "publisher": "Journal of Fluid Mechanics", "pagerange": "130-122", "id_number": "CaltechAUTHORS:PONjfm06", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:PONjfm06", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/S0022112006000590", "primary_object": { "basename": "PONjfm06.pdf", "url": "https://authors.library.caltech.edu/records/3zghb-r4x40/files/PONjfm06.pdf" }, "resource_type": "article", "pub_year": "2006", "author_list": "Ponchaut, N. F.; Hornung, H. G.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/69kts-82368", "eprint_id": 4126, "eprint_status": "archive", "datestamp": "2023-08-22 05:56:31", "lastmod": "2023-10-16 17:37:54", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Hill-D-J", "name": { "family": "Hill", "given": "D. J." } }, { "id": "Pantano-C", "name": { "family": "Pantano", "given": "C." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Large-eddy simulation and multiscale modelling of a Richtmyer\u2013Meshkov instability with reshock", "ispublished": "pub", "full_text_status": "public", "note": "\"Reprinted with the permission of Cambridge University Press.\" \n\n(Received July 6 2005). (Revised November 4 2005). Published online by Cambridge University Press 12 June 2006 \n\nThis work was supported by the Advanced Simulation and Computing (ASC) Program under subcontract no. B341492 of DOE contract W-7405-ENG-48. The authors would like to acknowledge the many helpful conversations with P. E. Dimotakis and D. I. Meiron.", "abstract": "Large-eddy simulations of the Richtmyer\u2013Meshkov instability with reshock are pre- sented and the results are compared with experiments. Several configurations of shocks initially travelling from light (air) to heavy (sulfur hexafluoride, SF6) have been simulated to match previous experiments and good agreement is found in the growth rates of the turbulent mixing zone (TMZ). The stretched-vortex subgrid model used in this study allows for subgrid continuation modelling, where statistics of the unresolved scales of the flow are estimated. In particular, this multiscale modelling allows the anisotropy of the flow to be extended to the dissipation scale, eta, and estimates to be formed for the subgrid probability density function of the mixture fraction of air/SF6 based on the subgrid variance, including the effect of Schmidt number.", "date": "2006-06-25", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "557", "publisher": "Journal of Fluid Mechanics", "pagerange": "29-61", "id_number": "CaltechAUTHORS:HILjfm06", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:HILjfm06", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/S0022112006009475", "primary_object": { "basename": "HILjfm06.pdf", "url": "https://authors.library.caltech.edu/records/69kts-82368/files/HILjfm06.pdf" }, "resource_type": "article", "pub_year": "2006", "author_list": "Hill, D. J.; Pantano, C.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/zaz99-gsz18", "eprint_id": 5366, "eprint_status": "archive", "datestamp": "2023-08-22 04:44:36", "lastmod": "2023-10-16 19:10:56", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pantano-C", "name": { "family": "Pantano", "given": "C." } }, { "id": "Deiterding-R", "name": { "family": "Deiterding", "given": "R." } }, { "id": "Hill-D-J", "name": { "family": "Hill", "given": "D. J." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "A low-numerical dissipation, patch-based adaptive-mesh-refinement method for large-eddy simulation of compressible flows", "ispublished": "pub", "full_text_status": "public", "note": "\u00a9 2006 IOP Publishing Limited \n\nThis work was supported by the Advanced Simulation and Computing (ASC) Program under subcontract no. B341492 of DOE contract W-7405-ENG-48. The authors would like to acknowledge the many helpful conversations with P.E. Dimotakis and D.I. Meiron. \n\nSciDAC 2006, SCIENTIFIC DISCOVERY THROUGH ADVANCED COMPUTING\n25\u201329 June 2006, Denver, Colorado, USA, Journal of Physics: Conference Series, Volume 46, 2006", "abstract": "This paper describes a hybrid finite-difference method for the large-eddy simulation of compressible flows with low-numerical dissipation and structured adaptive mesh refinement (SAMR). A conservative flux-based approach is described with an explicit centered scheme used in turbulent flow regions while a weighted essentially non-oscillatory (WENO) scheme is employed to capture shocks. Three-dimensional numerical simulations of a Richtmyer-Meshkov instability are presented.", "date": "2006", "date_type": "published", "publication": "Journal of Physics: Conference Series", "volume": "46", "publisher": "IOP", "pagerange": "48-52", "id_number": "CaltechAUTHORS:PANjpcs06", "issn": "1742-6596", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:PANjpcs06", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1088/1742-6596/46/1/006", "primary_object": { "basename": "PANjpcs06.pdf", "url": "https://authors.library.caltech.edu/records/zaz99-gsz18/files/PANjpcs06.pdf" }, "resource_type": "article", "pub_year": "2006", "author_list": "Pantano, C.; Deiterding, R.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/1qwm8-btd82", "eprint_id": 23049, "eprint_status": "archive", "datestamp": "2023-08-22 04:46:55", "lastmod": "2024-01-13 05:13:17", "type": "book_section", "metadata_visibility": "show", "creators": { "items": [ { "id": "Faddy-J-M", "name": { "family": "Faddy", "given": "J. M." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Evolution of vortex structures in a model of the turbulent trailing vortex", "ispublished": "unpub", "full_text_status": "restricted", "keywords": "trailing vortices; axial flow; M&M vortex", "note": "\u00a9 2006 Springer.", "abstract": "We present results obtained from a direct numerical simulation for a model of incompressible trailing vortices consisting of an array of counter-rotating vortices and a superposed axial velocity in a doubly-periodic domain, infinite in the vertical direction. The Reynolds number based on vortex circulation is 1000. It is found that for suffciently strong axial flow, helical instability modes develop on each vortex. This leads to a decrease in the magnitude of the axial flow and subsequent relaminarization of each vortex. At later times, modes corresponding to the more slowly growing co-operative instability become dominant. These produce their own helical structures followed by the rapid growth of small scales, then vorticity cancellation and decay of the vortex array. In the presence of strong axial flow the helical structure persists and the vortices appear more resistant to the breakdown phenomena than for arrays with no axial flow.", "date": "2006", "date_type": "published", "publisher": "Springer", "place_of_pub": "Dordrecht", "pagerange": "259-264", "id_number": "CaltechAUTHORS:20110322-102528073", "isbn": "1-4020-4180-2", "book_title": "IUTAM Symposium on Elementary Vortices and Coherent Structures : Significance in Turbulence Dynamics", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110322-102528073", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "contributors": { "items": [ { "id": "Kida-Shigeo", "name": { "family": "Kida", "given": "Shigeo" } } ] }, "doi": "10.1007/1-4020-4181-0", "resource_type": "book_section", "pub_year": "2006", "author_list": "Faddy, J. M. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/p87b4-j0k29", "eprint_id": 98297, "eprint_status": "archive", "datestamp": "2023-08-22 04:41:21", "lastmod": "2024-01-14 21:55:11", "type": "book_section", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Vortex tubes, spirals, and large-eddy simulation of turbulence", "ispublished": "unpub", "full_text_status": "restricted", "keywords": "Axial Velocity; Rotation Number; Suction Side; Vortex Tube; Passive Scalar", "note": "\u00a9 Kluwer Academic Publishers 2002. \n\nThis work was supported in part by the National Science Foundation under Grant CTS-9634222. Useful discussions with P. Dimotakis, T.S. Lundgren and T. Voelkl are gratefully acknowledged.", "abstract": "Progress in the quantitative modelling of turbulence using vortex-based models of the fine scales is reviewed. Recent work on the calculation of the spectrum of a passive scalar convecting and diffusing within a stretched-spiral vortex is briefly described. This is followed by a discussion of the application of ideas from the study of the vortex structure of the small scales of turbulence to the development of subgrid models for the large-eddy simulation (LES) of turbulent flows at large Reynolds numbers. Examples are given including the LES of rotating and non-rotating plane channel flow and of the mixing of a passive scalar by forced isotropic turbulence.", "date": "2005-12-16", "date_type": "published", "publisher": "Kluwer Academic Publishers", "place_of_pub": "Dordrecht", "pagerange": "171-180", "id_number": "CaltechAUTHORS:20190828-102317519", "isbn": "1402009801", "book_title": "Tubes, Sheets and Singularities in Fluid Dynamics", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190828-102317519", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF", "grant_number": "CTS-9634222" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "contributors": { "items": [ { "id": "Bajer-K", "name": { "family": "Bajer", "given": "K." } }, { "id": "Moffatt-H-K", "name": { "family": "Moffatt", "given": "H. K." } } ] }, "doi": "10.1007/0-306-48420-x_24", "resource_type": "book_section", "pub_year": "2005", "author_list": "Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/w8yxn-ggc59", "eprint_id": 2117, "eprint_status": "archive", "datestamp": "2023-08-22 04:11:26", "lastmod": "2023-10-13 23:13:00", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Wheatley-V", "name": { "family": "Wheatley", "given": "V." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Samtaney-Ravi", "name": { "family": "Samtaney", "given": "R." }, "orcid": "0000-0002-4702-6473" } ] }, "title": "Stability of an impulsively accelerated density interface in magnetohydrodynamics", "ispublished": "pub", "full_text_status": "public", "keywords": "plasma magnetohydrodynamics; plasma instability; plasma density; plasma simulation; plasma shock waves", "note": "\u00a92005 The American Physical Society. \n\nReceived 24 November 2004; published 14 September 2005. \n\nV.W. and D. I. P. are supported by the Academic Strategic Alliances Program of the Accelerated Strategic Computing Initiative (ASCI/ASAP) under subcontract No. B341492 of DOE Contract No. W-7405-ENG-48. R. S. was supported by USDOE Contract No. DEAC020-76-CH03073.", "abstract": "In the framework of ideal incompressible magnetohydrodynamics, we examine the stability of an impulsively accelerated, sinusoidally perturbed density interface in the presence of a magnetic field that is parallel to the acceleration. This is accomplished by analytically solving the linearized initial value problem, which is a model for the Richtmyer-Meshkov instability. We find that the initial growth rate of the interface is unaffected by the presence of a magnetic field, but for a finite magnetic field the interface amplitude asymptotes to a constant value. Thus the instability of the interface is suppressed. The interface behavior from the analytical solution is compared to the results of both linearized and nonlinear compressible numerical simulations.", "date": "2005-09-16", "date_type": "published", "publication": "Physical Review Letters", "volume": "95", "number": "12", "publisher": "American Physical Society", "pagerange": "Art. No. 125002", "id_number": "CaltechAUTHORS:WHEprl05", "issn": "0031-9007", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:WHEprl05", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1103/PhysRevLett.95.125002", "primary_object": { "basename": "WHEprl05.pdf", "url": "https://authors.library.caltech.edu/records/w8yxn-ggc59/files/WHEprl05.pdf" }, "resource_type": "article", "pub_year": "2005", "author_list": "Wheatley, V.; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/45j91-hkz11", "eprint_id": 2500, "eprint_status": "archive", "datestamp": "2023-08-22 04:01:34", "lastmod": "2023-10-13 23:34:01", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Faddy-J-M", "name": { "family": "Faddy", "given": "J. M." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Flow structure in a model of aircraft trailing vortices", "ispublished": "pub", "full_text_status": "public", "keywords": "aerodynamics; vortices; wakes; flow simulation; flow instability; turbulence", "note": "\u00a92005 American Institute of Physics \n\n(Received 8 December 2004; accepted 27 May 2005; published online 23 August 2005) \n\nThe authors (J.M.F. and D.I.P.) were supported in part by the National Science Foundation under Grant No. CTS-0227881. Access to the Hewlett-Packard V2500 computer, located at the California Institute of Technology, was provided by the Center for Advanced Computing Research.", "abstract": "We consider a model of incompressible trailing vortices consisting of an array of counter-rotating structures in a doubly periodic domain, infinite in the vertical direction. The two-dimensional vortex array of Mallier and Maslowe is combined with an axial velocity profile chosen proportional to the initial axial vorticity to provide an initial condition for the vortex wake. This base flow is a weak solution of the steady Euler equations with three velocity components that are functions of two spatial coordinates, thus allowing its linear stability properties to be investigated. These are used to interpret several stages in the development of vortex structure observed in fully three-dimensional direct numerical simulation (DNS) at Reynolds numbers Gamma/(2pinu)=[script O](1000). For sufficiently high axial velocity, its effect can be seen, in that each vortex in the linear array first develops helical structures before undergoing a period of relaminarization. At later times the more slowly growing cooperative elliptical instabilities become apparent, but the helical structure persists and the observed vortical structures remain coherent for longer periods than in the absence of axial velocity. Using the stretched-vortex subgrid model, large-eddy simulation runs are performed at large Reynolds numbers and a mixing transition identified at about Re=1\u20132\u00d710^4. Similar phenomena are observed in these simulations as are seen in the DNS.", "date": "2005-08-01", "date_type": "published", "publication": "Physics of Fluids", "volume": "17", "number": "8", "publisher": "Physics of Fluids", "pagerange": "Art. No. 085106", "id_number": "CaltechAUTHORS:FADpof05", "issn": "1070-6631", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:FADpof05", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.1955536", "primary_object": { "basename": "FADpof05.pdf", "url": "https://authors.library.caltech.edu/records/45j91-hkz11/files/FADpof05.pdf" }, "resource_type": "article", "pub_year": "2005", "author_list": "Faddy, J. M. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/9b22s-1nc67", "eprint_id": 5066, "eprint_status": "archive", "datestamp": "2023-08-22 03:45:53", "lastmod": "2023-10-16 18:05:43", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "O'Gorman-P-A", "name": { "family": "O'Gorman", "given": "P. A." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Effect of Schmidt number on the velocity\u2013scalar cospectrum in isotropic turbulence with a mean scalar gradient", "ispublished": "pub", "full_text_status": "public", "keywords": "DIRECT-INTERACTION APPROXIMATION; LAGRANGIAN RENORMALIZED APPROXIMATION; QUANTITIES LIKE TEMPERATURE; LARGE-EDDY SIMULATION; SUBGRID-STRESS MODEL; PASSIVE SCALAR; STRATIFIED TURBULENCE; INERTIAL RANGE; FINE-STRUCTURE; SPECTRUM", "note": "Copyright \u00a9 2005 Cambridge University Press. Reprinted with permission. \n\n(Received 29 June 2004 and in revised form 14 December 2004) Published online 27 May 2005 \n\nP.A.OG. and D.I.P. were supported in part by the National Science Foundation under Grant CTS-0227881. The DNS was performed on the QSC supercomputer, and was supported by the Academic Strategic Alliances Program of the Accelerated Strategic Computing Initiative (ASCI/ASAP) under subcontract no. B341492 of DOE contract W-7405-ENG-48.", "abstract": "We consider transport of a passive scalar by an isotropic turbulent velocity field in the presence of a mean scalar gradient. The velocity\u2013scalar cospectrum measures the distribution of the mean scalar flux across scales. An inequality is shown to bound the magnitude of the cospectrum in terms of the shell-summed energy and scalar spectra. At high Schmidt number, this bound limits the possible contribution of the sub-Kolmogorov scales to the scalar flux. At low Schmidt number, we derive an asymptotic result for the cospectrum in the inertial\u2013diffusive range, with a -11/3 power law wavenumber dependence, and a comparison is made with results from large-eddy simulation. The sparse direct-interaction perturbation (SDIP) is used to calculate the cospectrum for a range of Schmidt numbers. The Lumley scaling result is recovered in the inertial\u2013convective range and the constant of proportionality was calculated. At high Schmidt numbers, the cospectrum is found to decay exponentially in the viscous\u2013convective range, and at low Schmidt numbers, the -11/3 power law is observed in the inertial\u2013diffusive range. Results are reported for the cospectrum from a direct numerical simulation at a Taylor Reynolds number of 265, and a comparison is made at Schmidt number order unity between theory, simulation and experiment.", "date": "2005-06-10", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "532", "publisher": "Journal of Fluid Mechanics", "pagerange": "111-140", "id_number": "CaltechAUTHORS:OGOjfm05", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:OGOjfm05", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/S0022112005003903", "primary_object": { "basename": "OGOjfm05.pdf", "url": "https://authors.library.caltech.edu/records/9b22s-1nc67/files/OGOjfm05.pdf" }, "resource_type": "article", "pub_year": "2005", "author_list": "O'Gorman, P. A. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/rs4sx-q1292", "eprint_id": 327, "eprint_status": "archive", "datestamp": "2023-08-22 03:11:50", "lastmod": "2023-10-13 20:37:39", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "O'Reilly-G-K", "name": { "family": "O'Reilly", "given": "G. K." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Smooth transonic flow in an array of counter-rotating vortices", "ispublished": "pub", "full_text_status": "public", "note": "\"Reprinted with the permission of Cambridge University Press.\" \n\n(Received 28 July 2004 and in revised form 7 October 2004) \n\nThis work was supported by the Advanced Simulation Computing program (ASC) under subcontract no. B523297 of DOE contract W-7405-ENG-48.", "abstract": "Numerical solutions to the steady two-dimensional compressible Euler equations corresponding to a compressible analogue of the Mallier & Maslowe (Phys. Fluids, vol. A 5, 1993, p. 1074) vortex are presented. The steady compressible Euler equations are derived for homentropic flow and solved using a spectral method. A solution branch is parameterized by the inverse of the sound speed at infinity, $c_{\\infty}^{-1}$, and the mass flow rate between adjacent vortex cores of the corresponding incompressible solution, $\\epsilon$. For certain values of the mass flux, the solution branches followed numerically were found to terminate at a finite value of $c_{\\infty}^{-1}$. Along these branches numerical evidence for the existence of extensive regions of smooth steady transonic flow, with local Mach numbers as large as 1.276, is presented.", "date": "2005-02-10", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "524", "publisher": "Journal of Fluid Mechanics", "pagerange": "197-206", "id_number": "CaltechAUTHORS:OREjfm05", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:OREjfm05", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/S002211200400240X", "primary_object": { "basename": "OREjfm05.pdf", "url": "https://authors.library.caltech.edu/records/rs4sx-q1292/files/OREjfm05.pdf" }, "resource_type": "article", "pub_year": "2005", "author_list": "O'Reilly, G. K. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/5km2p-45w91", "eprint_id": 4285, "eprint_status": "archive", "datestamp": "2023-08-22 03:02:42", "lastmod": "2023-10-16 17:41:41", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Wheatley-V", "name": { "family": "Wheatley", "given": "V." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Samtaney-Ravi", "name": { "family": "Samtaney", "given": "R." }, "orcid": "0000-0002-4702-6473" } ] }, "title": "Regular shock refraction at an oblique planar density interface in magnetohydrodynamics", "ispublished": "pub", "full_text_status": "public", "keywords": "MHD INTERMEDIATE SHOCKS; IDEAL MAGNETOHYDRODYNAMICS; RIEMANN PROBLEMS; MAGNETIC-FIELD; WAVES; RECONNECTION; STABILITY; MODEL", "note": "Copyright \u00a9 2005 Cambridge University Press. Reprinted with permission. \n\nReceived 10 November 2003 and in revised form 2 July 2004. \n\nThe authors wish to thank Professor S.A.E.G. Falle of the University of Leeds for his useful comments and suggestions. V.W. and D.I.P. are supported by the Academic Strategic Alliances Program of the Accelerated Strategic Computing Initiative (ASCI/ASAP) under subcontract no. B341492 of DOE contract W-7405-ENG-48. R.S. is supported under the DOE SciDAC program (USDOE contract 208 no. DE-AC020-76-CH03073). This research used resources of the National Energy Research Scientific Computing Center, which is supported by the Office of Science of the US Department of Energy under contract no. DE-AC03-76SF00098.", "abstract": "We consider the problem of regular refraction (where regular implies all waves meet at a single point) of a shock at an oblique planar contact discontinuity separating conducting fluids of different densities in the presence of a magnetic field aligned with the incident shock velocity. Planar ideal magnetohydrodynamic (MHD) simulations indicate that the presence of a magnetic field inhibits the deposition of vorticity on the shocked contact. We show that the shock refraction process produces a system of five to seven plane waves that may include fast, intermediate, and slow MHD shocks, slow compound waves, 180\u25e6 rotational discontinuities, and slow-mode expansion fans that intersect at a point. In all solutions, the shocked contact is vorticity free and hence stable. These solutions are not unique, but differ in the types of waves that participate. The set of equations governing the structure of these multiple-wave solutions is obtained in which fluid property variation is allowed only in the azimuthal direction about the wave-intersection point. Corresponding solutions are referred to as either quintuple-points, sextuple-points, or septuple-points, depending on the number of participating waves. A numerical method of solution is described and examples are compared to the results of numerical simulations for moderate magnetic field strengths. The limit of vanishing magnetic field at fixed permeability and pressure is studied for two solution types. The relevant solutions correspond to the hydrodynamic triple-point with the shocked contact replaced by a singular structure consisting of a wedge, whose angle scales with the applied field magnitude, bounded by either two slow compound waves or two 180\u25e6 rotational discontinuities, each followed by a slow-mode expansion fan. These bracket the MHD contact which itself cannot support a tangential velocity jump in the presence of a non-parallel magnetic field. The magnetic field within the singular wedge is finite and the shock-induced change in tangential velocity across the wedge is supported by the expansion fans that form part of the compound waves or follow the rotational discontinuities. To verify these findings, an approximate leading-order asymptotic solution appropriate for both flow structures was computed. The full and asymptotic solutions are compared quantitatively.", "date": "2005-01-10", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "522", "publisher": "Journal of Fluid Mechanics", "pagerange": "179-214", "id_number": "CaltechAUTHORS:WHEjfm05", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:WHEjfm05", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/S0022112004001880", "primary_object": { "basename": "WHEjfm05.pdf", "url": "https://authors.library.caltech.edu/records/5km2p-45w91/files/WHEjfm05.pdf" }, "resource_type": "article", "pub_year": "2005", "author_list": "Wheatley, V.; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/6f4m7-cw041", "eprint_id": 25389, "eprint_status": "archive", "datestamp": "2023-08-19 14:16:47", "lastmod": "2023-10-24 15:50:17", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "O'Gorman-P-A", "name": { "family": "O'Gorman", "given": "P. A." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "On modal time correlations of turbulent velocity and scalar fields", "ispublished": "pub", "full_text_status": "restricted", "note": "\u00a9 2004 IOP Publishing Ltd.\n\nReceived 26 February 2004; Published 17 September 2004.\nAvailable online: 24 Jan 2011.\nPAOG and DIP were supported in part by the National Science Foundation under grant CTS-0227881. The DNS was performed on the QSC supercomputer and was supported by the Academic Strategic Alliances Program of the Accelerated Strategic Computing Initiative (ASCI/ASAP) under subcontract no. B341492 of DOE contract W-7405-ENG-48.", "abstract": "We consider Eulerian two-point, two-time correlations of a turbulent velocity field and those of a passive scalar mixed by a turbulent velocity field. Integral expressions are derived for the modal time-correlation functions of the velocity and scalar fields using the stretched-spiral vortex model. These expressions are evaluated using asymptotic methods for high wavenumber and, alternatively, using numerical integration. If the motion of the centres of the vortex structures is neglected, then an inertial time scaling (\u03b5k^2)^(\u22121/3), where \u03b5 is the energy dissipation rate and k the wavenumber, is found to collapse the velocity and scalar modal time-correlation functions to universal forms. Allowing the centres of the vortex structures to move introduces a sweeping time scale, (uk)^(\u22121), where u is the rms velocity of the centres of the vortex structures. The sweeping time scale dominates the inertial time scale for sufficiently large wavenumbers. Results are also reported for a direct numerical simulation of passive scalar mixing by a turbulent velocity field at a Taylor Reynolds number of 265. The velocity and scalar modal time-correlation functions were calculated in the simulation. They coincide for large enough wavenumbers and are found to collapse to universal forms when a sweeping time scale is used.", "date": "2004-09-17", "date_type": "published", "publication": "Journal of Turbulence", "volume": "5", "publisher": "Taylor and Francis", "pagerange": "Art. No. 35", "id_number": "CaltechAUTHORS:20110921-122858450", "issn": "1468-5248", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110921-122858450", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF", "grant_number": "CTS-0227881" }, { "agency": "Academic Strategic Alliances Program of the Accelerated Strategic Computing Initiative (ASCI/ASAP)", "grant_number": "B341492" }, { "agency": "Department of Energy (DOE)", "grant_number": "W-7405-ENG-48" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "resource_type": "article", "pub_year": "2004", "author_list": "O'Gorman, P. A. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/stysr-29t49", "eprint_id": 1313, "eprint_status": "archive", "datestamp": "2023-08-22 02:05:50", "lastmod": "2023-10-13 22:44:37", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Wang-Z-J", "name": { "family": "Wang", "given": "Z. Jane" }, "orcid": "0000-0001-9285-4051" } ] }, "title": "Unsteady forces on an accelerating plate and application to hovering insect flight", "ispublished": "pub", "full_text_status": "public", "note": "\"Reprinted with the permission of Cambridge University Press.\" \n\nReceived August 7 2003, Revised November 10 2003, Published Online 7 June 2004 \n\nD. I. P. wishes to thank P. E. Dimotakis for helpful discussions. Z. J.W. wishes to acknowledge the support by NSF Early Career grant, ONR YIP, AFOSR and the Packard Foundation.", "abstract": "The aerodynamic forces on a flat plate accelerating from rest at fixed incidence in two-dimensional power-law flow are studied analytically and numerically. An inviscid approximation is made in which separation at the two plate edges is modelled by growing spiral vortex sheets, whose evolution is determined by the Birkhoff\u2013Rott equation. A solution based on a similarity expansion is developed, valid when the scale of the separated vortex is much smaller than the plate dimension. The leading order is given by the well-known similarity growth of a vortex sheet from a semi-infinite flat plate, while equations at the second order describe the asymmetric sweeping effect of that component of the free-stream parallel to the plate. Owing to subtle cancellation, the unsteady vortex force exerted on the plate during the starting motion is independent of the sweeping effect and is determined by the similarity solution, to the order calculated. This gives a mechanism for dynamic stall based on a combination of unsteady vortex lift and pure added mass; the incidence angle for maximum vortex lift is $\\arccos \\sqrt{3/8}\\,{\\approx}\\,52.2^\\circ$ independent of the acceleration profile. Circulation on the flat plate makes no direct contribution. Both lift and drag force predictions from the unsteady inviscid theory are compared with those obtained from numerical solutions of the two-dimensional unsteady Navier\u2013Stokes equations for an ellipse of high aspect ratio, and with predictions of Wagner's classical theory. There is good agreement with numerical results at high incidence and moderate Reynolds number. The force per unit span predicted by the vortex theory is evaluated for parameters typical of insect wings and is found to be in reasonable agreement with numerical simulations. Estimates for the shed circulation and the size of the start-up vortices are also obtained. The significance of this flow as a mechanism for insect hovering flight is discussed.", "date": "2004-06-25", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "509", "publisher": "Cambridge University Press", "pagerange": "1-21", "id_number": "CaltechAUTHORS:PULjfm04", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:PULjfm04", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/S0022112004008821", "primary_object": { "basename": "PULjfm04.pdf", "url": "https://authors.library.caltech.edu/records/stysr-29t49/files/PULjfm04.pdf" }, "resource_type": "article", "pub_year": "2004", "author_list": "Pullin, D. I. and Wang, Z. Jane" }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/v73aw-m4x69", "eprint_id": 119128, "eprint_status": "archive", "datestamp": "2023-08-22 01:53:41", "lastmod": "2023-10-24 23:50:20", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pantano-Carlos", "name": { "family": "Pantano", "given": "C." }, "orcid": "0000-0003-3971-2278" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "A statistical description of turbulent diffusion flame holes", "ispublished": "pub", "full_text_status": "public", "keywords": "General Physics and Astronomy; Energy Engineering and Power Technology; Fuel Technology; General Chemical Engineering; General Chemistry", "note": "This work was supported by the ASC program of the Department of Energy under Subcontract B341492 of DOE Contract W-7405-ENG-48.", "abstract": "A statistical approach to the dynamics of diffusion-flame holes is presented. The dynamics of the holes are assumed to be controlled by the edge-flame velocity that is determined by the mixture fraction rate of dissipation, a random variable in a turbulent flow. The formulation is then specialized to the case of small circular holes and a stochastic model is used to investigate the dynamics of the joint probability density function of flame-hole radius and scalar dissipation. The associated Fokker\u2013Planck transport equation for the joint pdf is solved and the hole area evolution with time is computed. Furthermore, the one-dimensional marginal probability density function transport equation for the hole radius is derived and the conditional edge-flame velocity is studied for both expanding and collapsing holes.", "date": "2004-05", "date_type": "published", "publication": "Combustion and Flame", "volume": "137", "number": "3", "publisher": "Elsevier", "pagerange": "295-305", "id_number": "CaltechAUTHORS:20230209-935917000.2", "issn": "0010-2180", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230209-935917000.2", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Department of Energy (DOE)", "grant_number": "B341492" }, { "agency": "Department of Energy (DOE)", "grant_number": "W-7405-ENG-48" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1016/j.combustflame.2004.02.001", "resource_type": "article", "pub_year": "2004", "author_list": "Pantano, C. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/kzwng-baw43", "eprint_id": 119125, "eprint_status": "archive", "datestamp": "2023-08-22 01:41:13", "lastmod": "2023-10-24 23:50:13", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Hill-D-J", "name": { "family": "Hill", "given": "D. J." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Hybrid tuned center-difference-WENO method for large eddy simulations in the presence of strong shocks", "ispublished": "pub", "full_text_status": "public", "keywords": "Computer Science Applications; Physics and Astronomy (miscellaneous); Applied Mathematics; Computational Mathematics; Modeling and Simulation; Numerical Analysis", "note": "This work was supported by the Academic Strategic Alliances Program of the Accelerated Strategic Computing Initiative (ASCI/ASAP) under subcontract no. B341492 of DOE contract W-7405-ENG-48.", "abstract": "We develop a tuned center-difference (TCD) scheme optimized for large-eddy simulations (LES) using a method proposed by Ghosal. For LES of weakly compressible decaying turbulence, these optimized stencils are shown to provide superior performance when compared to higher-order centered schemes with the same stencil width. A hybrid method combining the TCD stencil with a weighted essentially non-oscillatory (WENO) method is then constructed for use in the LES of strongly compressible, shock-driven flows. The user-specified, optimum WENO weights are chosen to match those of the TCD scheme. It is expected that these weights will be achieved automatically in regions of smooth flow away from shocks, but in practice a switch is found to be necessary. The hybrid TCD\u2013WENO scheme is shown to work well for unsteady gas-dynamic flows in one and two dimensions.", "date": "2004-03-01", "date_type": "published", "publication": "Journal of Computational Physics", "volume": "194", "number": "2", "publisher": "Elsevier", "pagerange": "435-450", "id_number": "CaltechAUTHORS:20230209-338575000.1", "issn": "0021-9991", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230209-338575000.1", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Department of Energy (DOE)", "grant_number": "B341492" }, { "agency": "Department of Energy (DOE)", "grant_number": "W-7405-ENG-48" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1016/j.jcp.2003.07.032", "resource_type": "article", "pub_year": "2004", "author_list": "Hill, D. J. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/9xenj-mx423", "eprint_id": 4338, "eprint_status": "archive", "datestamp": "2023-08-22 01:05:00", "lastmod": "2023-10-16 17:42:48", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Gleeson-J-P", "name": { "family": "Gleeson", "given": "James P." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Flatness of tracer density profile produced by a point source in turbulence", "ispublished": "pub", "full_text_status": "public", "keywords": "Gaussian distribution; tracers; turbulence", "note": "\u00a92003 American Institute of Physics. \n\nReceived 25 November 2002; accepted 18 August 2003; published online 1 October 2003. \n\nThis project was partly funded by the Enterprise Ireland International Collaboration Fund, Science Foundation Ireland Investigator Award 02/IN.1/IM062, and by a research grant from the Faculty of Arts, University College Cork.", "abstract": "The average concentration of tracers advected from a point source by a multivariate normal velocity field is shown to deviate from a Gaussian profile. The flatness (kurtosis) is calculated using an asymptotic series expansion valid for velocity fields with short correlation times or weak space dependence. An explicit formula for the excess flatness at first order demonstrates maximum deviation from a Gaussian profile at time t of the order of five times the velocity correlation time, with a t\u20131 decay to the Gaussian value at large times. Monotonically decaying forms of the velocity time correlation function are shown to yield negative values for the first order excess flatness, but positive values can result when the correlation function has an oscillatory tail.", "date": "2003-11-01", "date_type": "published", "publication": "Physics of Fluids", "volume": "15", "number": "11", "publisher": "Physics of Fluids", "pagerange": "3546-3557", "id_number": "CaltechAUTHORS:GLEpof03", "issn": "1070-6631", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:GLEpof03", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.1616558", "primary_object": { "basename": "GLEpof03.pdf", "url": "https://authors.library.caltech.edu/records/9xenj-mx423/files/GLEpof03.pdf" }, "resource_type": "article", "pub_year": "2003", "author_list": "Gleeson, James P. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/8d6d6-q2x46", "eprint_id": 27406, "eprint_status": "archive", "datestamp": "2023-08-19 12:24:37", "lastmod": "2023-10-24 17:08:07", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "O'Reilly-Gerard-K", "name": { "family": "O'Reilly", "given": "G." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Structure and stability of the compressible Stuart vortex", "ispublished": "pub", "full_text_status": "public", "note": "\u00a9 2003 Cambridge University Press. \n\nReceived 30 December 2002 and in revised form 20 May 2003. \n\nThis work was supported by the Academic Strategic Alliances Program of the Accelerated Strategic Computing Initiative (ASCI/ASAP) under subcontract no. B341492 of DOE contract W-7405-ENG-48.\n\nPublished - OREjfm03.pdf
", "abstract": "The structure and two- and three-dimensional stability properties of a linear array of compressible Stuart vortices (CSV; Stuart 1967; Meiron et al. 2000) are investigated both analytically and numerically. The CSV is a family of steady, homentropic, two-dimensional solutions to the compressible Euler equations, parameterized by\nthe free-stream Mach number M_\u221e, and the mass flux _ inside a single vortex core. Known solutions have 0 < M_\u221e < 1. To investigate the normal-mode stability of the generally spatially non-uniform CSV solutions, the linear partial-differential equations describing the time evolution of small perturbations to the CSV base state are solved numerically using a normal-mode analysis in conjunction with a spectral method. The effect of increasing M_\u221e on the two main classes of instabilities found by Pierrehumbert & Widnall (1982) for the incompressible limit M_\u221e \u2192 0 is\nstudied. It is found that both two- and three-dimensional subharmonic instabilities cease to promote pairing events even at moderate M_\u221e. The fundamental mode becomes dominant at higher Mach numbers, although it ceases to peak strongly\nat a single spanwise wavenumber. We also find, over the range of \u03b5 investigated, a new instability corresponding to an instability on a parallel shear layer. The\nsignificance of these instabilities to experimental observations of growth in the compressible mixing layer is discussed. In an Appendix, we study the CSV equations\nwhen \u03b5 is small and M_\u221e is finite using a perturbation expansion in powers of \u03b5. An eigenvalue determining the structure of the perturbed vorticity and density fields is obtained from a singular Sturm\u2013Liouville problem for the stream-function perturbation at O(\u03b5). The resulting small-amplitude steady CSV solutions are shown to represent a bifurcation from the neutral point in the stability of a parallel shear layer with a tanh-velocity profile in a compressible inviscid perfect gas at uniform\ntemperature.", "date": "2003-10-25", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "493", "publisher": "Cambridge University Press", "pagerange": "231-254", "id_number": "CaltechAUTHORS:20111025-105659702", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20111025-105659702", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Department of Energy (DOE)", "grant_number": "B341492" }, { "agency": "Department of Energy (DOE)", "grant_number": "W-7405-ENG-48" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/S0022112003005913", "primary_object": { "basename": "OREjfm03.pdf", "url": "https://authors.library.caltech.edu/records/8d6d6-q2x46/files/OREjfm03.pdf" }, "resource_type": "article", "pub_year": "2003", "author_list": "O'Reilly, G. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/vg5zq-6qf95", "eprint_id": 6746, "eprint_status": "archive", "datestamp": "2023-08-22 00:23:41", "lastmod": "2023-10-16 20:30:49", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pantano-C", "name": { "family": "Pantano", "given": "C." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "On the dynamics of the collapse of a diffusion-flame hole", "ispublished": "pub", "full_text_status": "public", "keywords": "EDGE-FLAMES; MIXING LAYERS; TRIPLE FLAME; PROPAGATION; COUNTERFLOW", "note": "Copyright \u00a9 2003 Cambridge University Press. \n\nReceived September 19 2002; revised November 14 2002. \n\nThis work was supported by the Academic Strategic Alliances Program of the Accelerated Strategic Computing Initiative (ASCI/ASAP) under subcontract no. B341492 of DOE contract W-7405-ENG-48.", "abstract": "The collapse dynamics of a diffusion-flame hole in the presence of a counterflow are studied. We construct unsteady solutions of the one-dimensional edge-flame model of Buckmaster (1996), in which heat and mass transverse losses are algebraic. The flame structure is determined in the classical limit of large activation energy. Solutions for both planar and axisymmetric strain geometry are considered for the particular case of unity Lewis number. It is shown that the final stage of the edge-flame collapse is determined by a dominant balance between the time rate of change of the mass fractions (and temperature) and diffusion, giving a self-similar structure in which the size of the edge-flame hole approaches zero, to leading (zeroth) order, as a 1/2-power of time. This solution suggests an expansion of the full model equations in 1/2-powers of time that allows detailed analysis of the effects of side losses and flow distribution in the edge-flame collapse process. It is found that side loss effects are apparent at the first order, whereas convection by the counterflow is first felt during collapse at the second order in the fractional-time expansion. Numerical integrations of the governing equations are found to verify the analytic results.", "date": "2003-04-10", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "480", "publisher": "Journal of Fluid Mechanics", "pagerange": "311-332", "id_number": "CaltechAUTHORS:PANjfm03", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:PANjfm03", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "primary_object": { "basename": "PANjfm03.pdf", "url": "https://authors.library.caltech.edu/records/vg5zq-6qf95/files/PANjfm03.pdf" }, "resource_type": "article", "pub_year": "2003", "author_list": "Pantano, C. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/s5gsk-4k277", "eprint_id": 2785, "eprint_status": "archive", "datestamp": "2023-08-22 00:12:18", "lastmod": "2023-10-13 23:43:34", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "O'Gorman-P-A", "name": { "family": "O'Gorman", "given": "P. A." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "The velocity-scalar cross spectrum of stretched spiral vortices", "ispublished": "pub", "full_text_status": "public", "keywords": "vortices; turbulence", "note": "\u00a92003 American Institute of Physics. \n\n(Received 2 July 2002; accepted 17 October 2002; published online 19 December 2002) \n\nWe wish to thank L. Mydlardski for providing experimental data, and also P. Dimotakis for useful suggestions. P.A.O'G. and D.I.P. were supported in part by the National Science Foundation under Grant No. CTS-9978551.", "abstract": "The stretched-spiral vortex model is used to calculate the velocity-scalar cross spectrum for homogeneous, isotropic turbulence in the presence of a mean scalar gradient. The only nonzero component of the cospectrum is that contributed by the velocity component in the direction of the imposed scalar gradient while the quadrature spectrum is identically zero, in agreement with experiment. For the velocity field provided by the stretched-spiral vortex, the velocity-scalar spectrum can be divided into two additive components contributed by the velocity components along the vortex axis, and in the plane normal to this axis, respectively. For the axial velocity field, a new exact solution of the scalar convection-diffusion equation is found exhibiting scalar variation in the direction of the vortex tube axis. An asymptotic expression was found for the cospectrum contributed by this solution and the axial velocity, with the leading order term showing a k\u20135/3 range. This term is produced by the winding of the initial axial velocity field by the axisymmetric vortex core. The next order term gives a k\u20137/3 range, and arises from the lowest order effect of the nonaxisymmetric vorticity on the evolution of the axial velocity. Its coefficient can be of either sign or zero depending on the initial conditions. The contribution to the cospectrum from the velocity in the plane of the vortex is also calculated, but no universal high wave number asymptotic form is found. The integrals are evaluated numerically and it is found that the resulting cospectrum does not remain of one sign. Its form depends on the choice of the vortex core velocity profile and time cutoff in the spectral integrals. The one-dimensional cospectrum contributed by the axial velocity is compared with the experimental data of Mydlarski and Warhaft [J. Fluid Mech. 358, 135\u2013175 (1998)].", "date": "2003-02-01", "date_type": "published", "publication": "Physics of Fluids", "volume": "15", "number": "2", "publisher": "Physics of Fluids", "pagerange": "280-291", "id_number": "CaltechAUTHORS:OGOpof03", "issn": "1070-6631", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:OGOpof03", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.1527916", "primary_object": { "basename": "OGOpof03.pdf", "url": "https://authors.library.caltech.edu/records/s5gsk-4k277/files/OGOpof03.pdf" }, "resource_type": "article", "pub_year": "2003", "author_list": "O'Gorman, P. A. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/c63tz-y3d11", "eprint_id": 119222, "eprint_status": "archive", "datestamp": "2023-08-19 10:43:11", "lastmod": "2024-01-15 21:30:07", "type": "monograph", "metadata_visibility": "show", "creators": { "items": [ { "id": "O'Reilly-Gerard-K", "name": { "family": "O'Reilly", "given": "G." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Structure and stability of the compressible Stuart vortex", "ispublished": "unpub", "full_text_status": "public", "note": "This work was supported by the Academic Strategic Alliances Program of the Accelerated Strategic Computing Initiative (ASCI/ASAP) under subcontract no. B341492 of DOE contract W-7405-ENG-48.\n\nAccepted Version - cit-asci-tr166.pdf
", "abstract": "The structure and two- and three-dimensional stability properties of a linear array of compressible Stuart vortices (CSV; Stuart 1967; Meiron et al. 2000) are investigated both analytically and numerically. The CSV is a family of steady, homentropic, two-dimensional solutions to the compressible Euler equations, parameterized by the free-stream Mach number M_\u221e, and the mass flux _ inside a single vortex core. Known solutions have 0 < M_\u221e < 1. To investigate the normal-mode stability of the generally spatially non-uniform CSV solutions, the linear partial-differential equations describing the time evolution of small perturbations to the CSV base state are solved numerically using a normal-mode analysis in conjunction with a spectral method. The effect of increasing M_\u221e on the two main classes of instabilities found by Pierrehumbert & Widnall (1982) for the incompressible limit M_\u221e \u2192 0 is studied. It is found that both two- and three-dimensional subharmonic instabilities cease to promote pairing events even at moderate M_\u221e. The fundamental mode becomes dominant at higher Mach numbers, although it ceases to peak strongly at a single spanwise wavenumber. We also find, over the range of \u03b5 investigated, a new instability corresponding to an instability on a parallel shear layer. The significance of these instabilities to experimental observations of growth in the compressible mixing layer is discussed. In an Appendix, we study the CSV equations when \u03b5 is small and M_\u221e is finite using a perturbation expansion in powers of \u03b5. An eigenvalue determining the structure of the perturbed vorticity and density fields is obtained from a singular Sturm\u2013Liouville problem for the stream-function perturbation at O(\u03b5). The resulting small-amplitude steady CSV solutions are shown to represent a bifurcation from the neutral point in the stability of a parallel shear layer with a tanh-velocity profile in a compressible inviscid perfect gas at uniform temperature.", "date": "2003", "date_type": "published", "publisher": "AIP Conference Proceedings", "id_number": "CaltechAUTHORS:20230210-513731000.1", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230210-513731000.1", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Department of Energy (DOE)", "grant_number": "B341492" }, { "agency": "Department of Energy (DOE)", "grant_number": "W-7405-ENG-48" } ] }, "local_group": { "items": [ { "id": "Accelerated-Strategic-Computing-Initiative" }, { "id": "GALCIT" } ] }, "primary_object": { "basename": "cit-asci-tr166.pdf", "url": "https://authors.library.caltech.edu/records/c63tz-y3d11/files/cit-asci-tr166.pdf" }, "resource_type": "monograph", "pub_year": "2003", "author_list": "O'Reilly, G. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/ht1my-5m113", "eprint_id": 2086, "eprint_status": "archive", "datestamp": "2023-08-21 22:33:15", "lastmod": "2023-10-13 23:11:40", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Lundgren-T-S", "name": { "family": "Lundgren", "given": "T. S." } } ] }, "title": "Axial motion and scalar transport in stretched spiral vortices", "ispublished": "pub", "full_text_status": "public", "keywords": "vortices; turbulence", "note": "Copyright \u00a9 2001 American Institute of Physics. \n\nReceived 29 November 2000; accepted 10 May 2001. \n\nD.I.P. was supported in part by the National Science Foundation under Grant No. CTS-9978551.", "abstract": "We consider the dynamics of axial velocity and of scalar transport in the stretched-spiral vortex model of turbulent fine scales. A large-time asymptotic solution to the scalar advection-diffusion equation, with an azimuthal swirling velocity field provided by the stretched spiral vortex, is used together with appropriate stretching transformations to determine the evolution of both the axial velocity and a passive scalar. This allows calculation of the shell-integrated three-dimensional spectra of these quantities for the spiral-vortex flow. The dominant term in the velocity (energy) spectrum contributed by the axial velocity is found to be produced by the stirring of the initial distribution of axial velocity by the axisymmetric component of the azimuthal velocity. This gives a k(-7/3) spectrum at large wave numbers, compared to the k(-5/3) component for the azimuthal velocity itself. The spectrum of a passive scalar being mixed by the vortex velocity field is the sum of two power laws. The first is a k(-1) Batchelor spectrum for wave numbers up to the inverse Batchelor scale. This is produced by the axisymmetric component of the axial vorticity but is independent of the detailed radial velocity profile. The second is a k(-5/3) Obukov-Corrsin spectrum for wave numbers less than the inverse Kolmogorov scale. This is generated by the nonaxisymmetric axial vorticity and depends on initial correlations between this vorticity and the initial scalar field. The one-dimensional scalar spectrum for the composite model is in satisfactory agreement with experimental measurement.", "date": "2001-09-01", "date_type": "published", "publication": "Physics of Fluids", "volume": "13", "number": "9", "publisher": "Physics of Fluids", "pagerange": "2553-2563", "id_number": "CaltechAUTHORS:PULpof01", "issn": "1070-6631", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:PULpof01", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.1388207", "primary_object": { "basename": "PULpof01.pdf", "url": "https://authors.library.caltech.edu/records/ht1my-5m113/files/PULpof01.pdf" }, "resource_type": "article", "pub_year": "2001", "author_list": "Pullin, D. I. and Lundgren, T. S." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/xxe0g-swa27", "eprint_id": 1988, "eprint_status": "archive", "datestamp": "2023-08-21 22:23:40", "lastmod": "2023-10-13 23:07:47", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Aivazis-K-A", "name": { "family": "Aivazis", "given": "Keri A." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "On velocity structure functions and the spherical vortex model for isotropic turbulence", "ispublished": "pub", "full_text_status": "public", "keywords": "turbulence; vortices; stochastic processes", "note": "\u00a92001 American Institute of Physics. \n\n(Received 30 November 2000; accepted 6 March 2001) \n\nThe authors acknowledge many useful discussions with Philip Saffman. We also thank Patrick Tabeling for supplying detailed measurements of longitudinal velocity structure functions.", "abstract": "We investigate a stochastic model for homogeneous, isotropic turbulence based on Hill's spherical vortex. This is an extension of the method of Synge and Lin [Trans. R. Soc. Can. 37, 45 (1943)], to the calculation of higher even-order velocity structure functions. Isotropic turbulence is represented by a homogeneous distribution of eddies, each modeled by a spherical vortex. The cascade process of eddy breakdown is incorporated into the statistical model through an average over an assumed log-normal distribution of vortex radii. We calculate the statistical properties of the model, in particular order-n velocity structure functions defined by rank-n tensors for the ensemble average of a set of incremental differences in velocity components. We define Di[centered ellipsis]s = <(ui(x + xi )\u2013ui(x))[centered ellipsis](us(x + xi )\u2013us(x))>, where <[centered ellipsis]> denotes the ensemble average. Specifically Dij, Dijkl, and the longitudinal component of Dijklmn are calculated directly from the spherical vortex ensemble. Matching the longitudinal components of Dij and Dijkl with experimental results fixes two independent model parameters. The lateral and mixed components of Dijkl and the longitudinal component of Dijklmn are then model predictions.", "date": "2001-07-01", "date_type": "published", "publication": "Physics of Fluids", "volume": "13", "number": "7", "publisher": "Physics of Fluids", "pagerange": "2019-2029", "id_number": "CaltechAUTHORS:AIVpof01", "issn": "1070-6631", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:AIVpof01", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.1367870", "primary_object": { "basename": "AIVpof01.pdf", "url": "https://authors.library.caltech.edu/records/xxe0g-swa27/files/AIVpof01.pdf" }, "resource_type": "article", "pub_year": "2001", "author_list": "Aivazis, Keri A. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/fhykm-ank15", "eprint_id": 2399, "eprint_status": "archive", "datestamp": "2023-08-21 21:33:07", "lastmod": "2023-10-13 23:27:11", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "A vortex-based model for the subgrid flux of a passive scalar", "ispublished": "pub", "full_text_status": "public", "keywords": "turbulence; vortices; flow simulation", "note": "\u00a92000 American Institute of Physics. \n\n(Received 29 September 1999; accepted 1 June 2000) \n\nThis work was supported in part by the National Science Foundation under Grant No. CTS-9978551.", "abstract": "A model for the flux of a passive scalar by the subgrid motions in the large-eddy simulation of turbulent flow is proposed within the framework of the stretched-vortex subgrid stress model. The model is based on an analytical solution for the winding of a scalar field by an elemental subgrid vortex. This gives a tensor gradient-diffusion expression for the local flux of the scalar with subgrid turbulent diffusivity which depends upon the subgrid energy, the local cell size, and the vortex orientation in space. The scalar-flux subgrid model is tested by comparison of the results of 323 large-eddy simulation of passive-scalar transport by forced isotropic turbulence in the presence of a mean scalar gradient, with the direct-numerical simulation results of Overholt and Pope [Phys. Fluids 8, 2128 (1996)]. The present large-eddy simulation results predict that at large Taylor\u2013Reynolds numbers, the ratio of the scalar variance to the squared product of the scalar gradient with the dissipation length of the turbulence, is asymptotic to a nearly constant value c[prime]2/(alpha1 Lepsilon)2[approximate]0.36.", "date": "2000-09-01", "date_type": "published", "publication": "Physics of Fluids", "volume": "12", "number": "9", "publisher": "Physics of Fluids", "pagerange": "2311-2319", "id_number": "CaltechAUTHORS:PULpof00", "issn": "1070-6631", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:PULpof00", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.1287512", "primary_object": { "basename": "PULpof00.pdf", "url": "https://authors.library.caltech.edu/records/fhykm-ank15/files/PULpof00.pdf" }, "resource_type": "article", "pub_year": "2000", "author_list": "Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/cq7y4-20j79", "eprint_id": 2257, "eprint_status": "archive", "datestamp": "2023-08-21 21:19:00", "lastmod": "2023-10-13 23:17:27", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Voelkl-T", "name": { "family": "Voelkl", "given": "Tobias" } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Chan-Daniel-C", "name": { "family": "Chan", "given": "Daniel C." } } ] }, "title": "A physical-space version of the stretched-vortex subgrid-stress model for large-eddy simulation", "ispublished": "pub", "full_text_status": "public", "keywords": "flow simulation; vortices; turbulence; fluctuations; channel flow", "note": "Copyright \u00a9 2000 American Institute of Physics. \n\nReceived 15 July 1999; accepted 14 March 2000. \n\nThis work was supported in part by the National Science Foundation under Grant No. CTS-9634222. The channel flow simulations were greatly facilitated by the availability of the Cray T3E at the Pittsburgh Supercomputing Center (PSC) under the Academic Strategic Alliances Program of the Accelerated Strategic Computing Initiative (ASCI/ASAP). Additional computations were performed on the ASCI Bluemountain computer at Los Alamos National Laboratory, and its availability for this work is also gratefully acknowledged.", "abstract": "A physical-space version of the stretched-vortex subgrid-stress model is presented and applied to large-eddy simulations of incompressible flows. This version estimates the subgrid-kinetic energy required for evaluation of the subgrid-stress tensor using local second-order structure-function information of the resolved velocity field at separations of order the local cell size. A relation between the structure function and the energy spectrum is derived using the kinematic assumptions of the stretched-vortex model for locally homogeneous anisotropic turbulence. Results of large-eddy simulations using this model are compared to experimental and direct numerical simulation data. Comparisons are shown for the decay of kinetic energy and energy spectra of decaying isotropic turbulence and for mean velocities, root-mean-square velocity fluctuations and turbulence-kinetic energy balances of channel flow at three different Reynolds numbers.", "date": "2000-07", "date_type": "published", "publication": "Physics of Fluids", "volume": "12", "number": "7", "publisher": "Physics of Fluids", "pagerange": "1810-1825", "id_number": "CaltechAUTHORS:VOEpof00", "issn": "1070-6631", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:VOEpof00", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.870429", "primary_object": { "basename": "VOEpof00.pdf", "url": "https://authors.library.caltech.edu/records/cq7y4-20j79/files/VOEpof00.pdf" }, "resource_type": "article", "pub_year": "2000", "author_list": "Voelkl, Tobias; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/ze1kg-b2m72", "eprint_id": 9053, "eprint_status": "archive", "datestamp": "2023-08-21 21:07:47", "lastmod": "2023-10-16 21:53:24", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Meiron-D-I", "name": { "family": "Meiron", "given": "D. I." }, "orcid": "0000-0003-0397-3775" }, { "id": "Moore-D-W", "name": { "family": "Moore", "given": "D. W." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "On steady compressible flows with compact vorticity; the compressible Stuart vortex", "ispublished": "pub", "full_text_status": "public", "note": "\u00a9 Cambridge University Press 2000. Reprinted with permission. \n\n(Received 20 January 1999 and in revised form 1 June 1999)\n\nPublished - MEIjfm00.pdf
", "abstract": "Numerical and analytical solutions to the steady compressible Euler equations corresponding to a compressible analogue of the linear Stuart vortex array are presented. These correspond to a homentropic continuation, to finite Mach number, of the Stuart solution describing a linear vortex array in an incompressible fluid. The appropriate partial differential equations describing the flow correspond to the compressible homentropic Euler equations in two dimensions, with a prescribed vorticity\u2013density\u2013streamfunction relationship. In order to construct a well-posed problem for this continuation, it was found, unexpectedly, to be necessary to introduce an eigenvalue into the vorticity\u2013density\u2013streamfunction equation. In the Rayleigh\u2013Janzen expansion of solutions in even powers of the free-stream Mach number M[infty infinity], this eigenvalue is determined by a solvability condition. Accurate numerical solution by both finite-difference and spectral methods are presented for the compressible Stuart vortex, over a range of M[infty infinity], and of a parameter corresponding to a confined mass-flow rate. These also confirm the nonlinear eigenvalue character of the governing equations. All solution branches followed numerically were found to terminate when the maximum local Mach number just exceeded unity. For one such branch we present evidence for the existence of a very small range of M[infty infinity] over which smooth transonic shock-free flow can occur.", "date": "2000-04-25", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "409", "publisher": "Cambridge University Press", "pagerange": "29-49", "id_number": "CaltechAUTHORS:MEIjfm00", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:MEIjfm00", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/S0022112099007752", "primary_object": { "basename": "MEIjfm00.pdf", "url": "https://authors.library.caltech.edu/records/ze1kg-b2m72/files/MEIjfm00.pdf" }, "resource_type": "article", "pub_year": "2000", "author_list": "Meiron, D. I.; Moore, D. W.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/rf1hm-zdn60", "eprint_id": 1878, "eprint_status": "archive", "datestamp": "2023-08-22 14:07:59", "lastmod": "2023-10-13 23:03:47", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Brady-M", "name": { "family": "Brady", "given": "M." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "On singularity formation in three-dimensional vortex sheet evolution", "ispublished": "pub", "full_text_status": "public", "keywords": "vortices; flow instability; motion", "note": "Copyright \u00a9 1999 American Institute of Physics. \n\nReceived 6 April 1999; accepted 10 June 1999. \n\nThis work was partially supported by NSF Grant No. CTS 9634222. The authors are grateful for useful discussions with S. J. Cowley.", "abstract": "It is shown that if a doubly-infinite vortex sheet has cylindrical shape and strength distributions at some initial time, then this property is retained in its subsequent evolution. It is also shown that in planes normal to the generator of the cylindrical sheet geometry, the nonlinear evolution of the sheet is the same as that of an equivalent strictly two-dimensional sheet motion. These properties are used to show that when an initially flat vortex sheet is subject to a finite-amplitude, three-dimensional normal mode perturbation, weak singularities develop along lines which are oblique to the undisturbed velocity jump vector at a time that can be inferred from an extension of Moore's [Proc. R. Soc. A 365, 105 (1979)] result for two-dimensional motion.", "date": "1999-11-01", "date_type": "published", "publication": "Physics of Fluids", "volume": "11", "number": "11", "publisher": "Physics of Fluids", "pagerange": "3198-3200", "id_number": "CaltechAUTHORS:BRApof99", "issn": "1070-6631", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:BRApof99", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.870216", "primary_object": { "basename": "BRApof99.pdf", "url": "https://authors.library.caltech.edu/records/rf1hm-zdn60/files/BRApof99.pdf" }, "resource_type": "article", "pub_year": "1999", "author_list": "Brady, M. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/ftxb1-71311", "eprint_id": 104382, "eprint_status": "archive", "datestamp": "2023-08-19 03:50:12", "lastmod": "2023-10-20 20:24:12", "type": "book_section", "metadata_visibility": "show", "creators": { "items": [ { "id": "Voelkl-T", "name": { "family": "Voelkl", "given": "T." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Henderson-R-D", "name": { "family": "Henderson", "given": "R. D." } } ] }, "title": "The Stretched-Vortex SGS Model in Physical Space", "ispublished": "unpub", "full_text_status": "restricted", "note": "\u00a9 1999 Springer Science+Business Media Dordrecht. \n\nThis work was supported partially by the National Science Foundation under Grant CTS-9634222 and partially by the Academic Strategic Alliances Program of the Accelerated Strategic Computing Initiative (ASCII ASAP) under subcontract no. B341492 of DOE contract W-7405-ENG-48.", "abstract": "The stretched-vortex subgrid stress model for the large-eddy simulation of turbulent flows has been developed to the stage where it can be applied to realistic flow at large Reynolds numbers [1] [2]. The basic assumption of this model [3] is that the subgrid vortex structure consists of straight, stretched vortices containing a nearly axisymmetric subgrid vorticity field. Vortices of this type, such as the Burgers vortex and the stretched-spiral vortex have provided fair quantitative estimates of turbulence fine-scale properties [4]. These structures are probably an oversimplified model of fine-scale turbulence, but may nevertheless contain sufficient of the vortex-stretching and energy cascade physics characteristic of the small scales to provide a reasonable basis for subgrid-stress modelling for LES. The resulting subgrid stresses are\n\u03a4_(ij)=K(\u03b4_(ij)\u2212e^v_ie^v_j).\n(1)\nwhere K is the subgrid energy and e_i^ v , i = 1, 2, 3 are the direction cosines of the subgrid vortex axis. The local subgrid dissipation \u03f5_(sgs) is equal to the product of K with the component of S_(ij) aligned with the vortex axis. A class of simple models is obtained when it is assumed that the subgrid vortices are aligned with the eigenvectors of the rate-of-strain tensor S_(ij) [1]. Utilizing an assumed Kolmogorov form for the local subgrid energy spectrum, the model estimates the turbulent energy production at the resolved-scale cutoff in terms of the model parameters \u03f5 and the Kolmogorov prefactor K\u2080 and adjusts these parameters locally so as to continue the cascade through the cutoff to the subgrid vortex structures where the dissipation takes place.", "date": "1999", "date_type": "published", "publisher": "Springer", "place_of_pub": "Dordrecht", "pagerange": "459-464", "id_number": "CaltechAUTHORS:20200714-123705635", "isbn": "978-94-010-5924-4", "book_title": "Recent Advances in DNS and LES", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200714-123705635", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF", "grant_number": "CTS-9634222" }, { "agency": "Department of Energy (DOE)", "grant_number": "B341492" }, { "agency": "Department of Energy (DOE)", "grant_number": "W-7405-ENG-48" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "contributors": { "items": [ { "id": "Knight-D", "name": { "family": "Knight", "given": "Doyle" } }, { "id": "Sakell-L", "name": { "family": "Sakell", "given": "Leonidas" } } ] }, "doi": "10.1007/978-94-011-4513-8_39", "resource_type": "book_section", "pub_year": "1999", "author_list": "Voelkl, T.; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/vap4d-1yk87", "eprint_id": 28837, "eprint_status": "archive", "datestamp": "2023-08-19 03:31:27", "lastmod": "2023-10-24 18:11:04", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Moore-D-W", "name": { "family": "Moore", "given": "D. W." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "On steady compressible flows with compact vorticity; the compressible Hill's spherical vortex", "ispublished": "pub", "full_text_status": "public", "note": "\u00a9 1998 Cambridge University Press. Received 5 December 1997 and in revised form 18 June 1998. Published online: 08 September 2000. D.I.P. was partly supported by a grant from the EPSERC of the UK. We acknowledge a referee who pointed out the relevance of the Munk-Prim transformation.\n\nPublished - S0022112098002675a.pdf
", "abstract": "We consider steady compressible Euler flow corresponding to the compressible analogue of the well-known incompressible Hill's spherical vortex (HSV). We first derive appropriate compressible Euler equations for steady homentropic flow and show how these may be used to define a continuation of the HSV to finite Mach number M_\u221e =U_\u221e/C_\u221e, where U_\u221e, C_\u221e are the fluid velocity and speed of sound at infinity respectively. This is referred to as the compressible Hill's spherical vortex (CHSV). It corresponds to axisymmetric compressible Euler flow in which, within a vortical bubble, the azimuthal vorticity divided by the product of the density and the distance to the axis remains constant along streamlines, with irrotational flow outside the bubble. The equations are first solved numerically using a fourth-order finite-difference method, and then using a Rayleigh\u2013Janzen expansion in powers of M^2_\u221e to order M^4_\u221e. When M_\u221e > 0, the vortical bubble is no longer spherical and its detailed shape must be determined by matching conditions consisting of continuity of the fluid velocity at the bubble boundary. For subsonic compressible flow the bubble boundary takes an approximately prolate spheroidal shape with major axis aligned along the flow direction. There is good agreement between the perturbation solution and Richardson extrapolation of the finite difference solutions for the bubble boundary shape up to M_\u221e equal to 0.5. The numerical solutions indicate that the flow first becomes locally sonic near or at the bubble centre when M_\u221e \u2248 0.598 and a singularity appears to form at the sonic point. We were unable to find shock-free steady CHSVs containing regions of locally supersonic flow and their existence for the present continuation of the HSV remains an open question.", "date": "1998-11-10", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "374", "publisher": "Cambridge University Press", "pagerange": "285-303", "id_number": "CaltechAUTHORS:20120118-133600629", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120118-133600629", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "EPSRC (UK)" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/S0022112098002675", "primary_object": { "basename": "S0022112098002675a.pdf", "url": "https://authors.library.caltech.edu/records/vap4d-1yk87/files/S0022112098002675a.pdf" }, "resource_type": "article", "pub_year": "1998", "author_list": "Moore, D. W. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/bcgzy-ntg14", "eprint_id": 3175, "eprint_status": "archive", "datestamp": "2023-08-22 12:52:41", "lastmod": "2023-10-16 15:41:22", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Prochazka-A", "name": { "family": "Prochazka", "given": "Aurelius" } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Structure and stability of non-symmetric Burgers vortices", "ispublished": "pub", "full_text_status": "public", "keywords": "HOMOGENEOUS TURBULENCE; ISOTROPIC TURBULENCE; STRETCHED VORTICES; INTENSE VORTICITY; MODELS; VORTEX; INTERMITTENCY; ALIGNMENT; DYNAMICS; STRAIN", "note": "\"Reprinted with the permission of Cambridge University Press.\" \n\n(Received February 2 1997; Revised December 2 1997) \n\nWe gratefully acknowledge helpful discussions with David Hill, James Buntine, and Ron Henderson. This research was partial supported by NSF Grant CTS-9634222.", "abstract": "We investigate, numerically and analytically, the structure and stability of steady and quasi-steady solutions of the Navier\u2013Stokes equations corresponding to stretched vortices embedded in a uniform non-symmetric straining field, ([alpha]x, [beta]y, [gamma]z), [alpha]+[beta]+[gamma]=0, one principal axis of extensional strain of which is aligned with the vorticity. These are known as non-symmetric Burgers vortices (Robinson & Saffman 1984). We consider vortex Reynolds numbers R=[Gamma]/(2[pi]v) where [Gamma] is the vortex circulation and v the kinematic viscosity, in the range R=1[minus sign]104, and a broad range of strain ratios [lambda]=([beta][minus sign][alpha])/([beta]+[alpha]) including [lambda]>1, and in some cases [lambda][dbl greater-than sign]1. A pseudo-spectral method is used to obtain numerical solutions corresponding to steady and quasi-steady vortex states over our whole (R, [lambda]) parameter space including [lambda] where arguments proposed by Moffatt, Kida & Ohkitani (1994) demonstrate the non-existence of strictly steady solutions. When [lambda][dbl greater-than sign]1, R[dbl greater-than sign]1 and [epsilon][identical with][lambda]/R[double less-than sign]1, we find an accurate asymptotic form for the vorticity in a region 11. An iterative technique based on the power method is used to estimate the largest eigenvalues for the non-symmetric case [lambda]>0. Stability is found for 0[less-than-or-eq, slant][lambda][less-than-or-eq, slant]1, and a neutrally convective mode of instability is found and analysed for [lambda]>1. Our general conclusion is that the generalized non-symmetric Burgers vortex is unconditionally stable to two-dimensional disturbances for all R, 0[less-than-or-eq, slant][lambda][less-than-or-eq, slant]1, and that when [lambda]>1, the vortex will decay only through exponentially slow leakage of vorticity, indicating extreme robustness in this case.", "date": "1998-05-25", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "363", "publisher": "Journal of Fluid Mechanics", "pagerange": "199-228", "id_number": "CaltechAUTHORS:PROjfm98", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:PROjfm98", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "primary_object": { "basename": "PROjfm98.pdf", "url": "https://authors.library.caltech.edu/records/bcgzy-ntg14/files/PROjfm98.pdf" }, "resource_type": "article", "pub_year": "1998", "author_list": "Prochazka, Aurelius and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/hcykn-fcp93", "eprint_id": 328, "eprint_status": "archive", "datestamp": "2023-08-22 12:30:19", "lastmod": "2023-10-13 20:37:41", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Saffman-P-G", "name": { "family": "Saffman", "given": "P. G." } } ] }, "title": "Vortex dynamics in turbulence", "ispublished": "pub", "full_text_status": "public", "keywords": "decay of turbulence, high Reynolds number", "note": "\u00a9 1998 by Annual Reviews Inc. \n\nDIP was partially supported by National Science Foundation (NSF) Grant No. CTS-9634222 and PGS was partially supported by the Department of Energy under Grant No. DE-FG03-89ER25073 and by NSF Grant No. DMS-9423245.\n\nPublished - PULarfm98.pdf
", "abstract": "We survey attempts to construct vortex models of the inertial-range and fine-scale range of high Reynolds number turbulence. An emphasis is placed on models capable of quantitative predictions or postdictions.", "date": "1998-01", "date_type": "published", "publication": "Annual Review of Fluid Mechanics", "volume": "30", "publisher": "Annual Reviews", "pagerange": "31-51", "id_number": "CaltechAUTHORS:PULarfm98", "issn": "0066-4189", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:PULarfm98", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF", "grant_number": "CTS-9634222" }, { "agency": "Department of Energy (DOE)", "grant_number": "DE-FG03-89ER25073" }, { "agency": "NSF", "grant_number": "DMS-9423245" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1146/annurev.fluid.30.1.31", "primary_object": { "basename": "PULarfm98.pdf", "url": "https://authors.library.caltech.edu/records/hcykn-fcp93/files/PULarfm98.pdf" }, "resource_type": "article", "pub_year": "1998", "author_list": "Pullin, D. I. and Saffman, P. G." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/gys5p-b0032", "eprint_id": 3089, "eprint_status": "archive", "datestamp": "2023-08-22 11:51:12", "lastmod": "2023-10-16 15:36:36", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Misra-A", "name": { "family": "Misra", "given": "Ashish" } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "A vortex-based subgrid stress model for large-eddy simulation", "ispublished": "pub", "full_text_status": "public", "keywords": "flow simulation; turbulence; vortices; Navier-Stokes equations", "note": "\u00a91997 American Institute of Physics. \n\nReceived 24 September 1996; accepted 16 April 1997. \n\nThis work was supported in part by NSF Grant CTS-9634222. The authors wish to thank Dr. Thomas Lund for useful discussions and help in the implementation of the decaying test. AM benefited from his visit to CTR during the 1996 Summer Program and would like to thank Professor Parviz Moin for useful suggestions.", "abstract": "A class of subgrid stress (SGS) models for large-eddy simulation (LES) is presented based on the idea of structure-based Reynolds-stress closure. The subgrid structure of the turbulence is assumed to consist of stretched vortices whose orientations are determined by the resolved velocity field. An equation which relates the subgrid stress to the structure orientation and the subgrid kinetic energy, together with an assumed Kolmogorov energy spectrum for the subgrid vortices, gives a closed coupling of the SGS model dynamics to the filtered Navier-Stokes equations for the resolved flow quantities. The subgrid energy is calculated directly by use of a local balance between the total dissipation and the sum of the resolved-scale dissipation and production by the resolved scales. Simple one- and two-vortex models are proposed and tested in which the subgrid vortex orientations are either fixed by the local resolved velocity gradients, or rotate in response to the evolution of the gradient field. These models are not of the eddy viscosity type. LES calculations with the present models are described for 32^(3) decaying turbulence and also for forced 32^(3) box turbulence at Taylor Reynolds numbers R-lambda in the range R(lambda)similar or equal to 30 (fully resolved) to R-lambda=infinity. The models give good agreement with experiment for decaying turbulence and produce negligible SGS dissipation for forced turbulence in the limit of fully resolved flow.", "date": "1997-08-01", "date_type": "published", "publication": "Physics of Fluids", "volume": "9", "number": "8", "publisher": "Physics of Fluids", "pagerange": "2443-2454", "id_number": "CaltechAUTHORS:MISpof97", "issn": "1070-6631", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:MISpof97", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.869361", "primary_object": { "basename": "MISpof97.pdf", "url": "https://authors.library.caltech.edu/records/gys5p-b0032/files/MISpof97.pdf" }, "resource_type": "article", "pub_year": "1997", "author_list": "Misra, Ashish and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/mcfft-p3h92", "eprint_id": 9609, "eprint_status": "archive", "datestamp": "2023-08-22 11:19:35", "lastmod": "2023-10-16 22:23:02", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Saffman-P-G", "name": { "family": "Saffman", "given": "P. G." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Calculation of velocity structure functions for vortex models of isotropic turbulence", "ispublished": "pub", "full_text_status": "public", "keywords": "SPIRAL VORTEX", "note": "\u00a91996 American Institute of Physics. \n\nReceived 1 March 1996; accepted 16 July 1996. \n\nThe authors wish to thank Patrick Tabeling for supplying unpublished measurements of longitudinal velocity structure functions. D.I.P. was partially supported by NSF Grant No. CTS-9311811 and P.G.S. was partially supported by the Department of Energy under Grant No. DE-FG03-89ER25073. We thank Dan Meiron and Donal Gallagher for helping with the asymptotic expansion of (34) for large r.", "abstract": "Velocity structure functions (u'p\u2013up)m are calculated for vortex models of isotropic turbulence. An integral operator is introduced which defines an isotropic two-point field from a volume-orientation average for a specific solution of the Navier\u2013Stokes equations. Applying this to positive integer powers of the longitudinal velocity difference then gives explicit formulas for (u'p\u2013up)m as a function of order m and of the scalar separation r. Special forms of the operator are then obtained for rectilinear stretched vortex models of the Townsend\u2013Lundgren type. Numerical results are given for the Burgers vortex and also for a realization of the Lundgren-strained spiral vortex, and comparison with experimental measurement is made. In an Appendix, we calculate values of the velocity-derivative moments for the Townsend\u2013Burgers model.", "date": "1996-11-01", "date_type": "published", "publication": "Physics of Fluids", "volume": "8", "number": "11", "publisher": "Physics of Fluids", "pagerange": "3072-3084", "id_number": "CaltechAUTHORS:SAFpof96", "issn": "1070-6631", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:SAFpof96", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.869081", "primary_object": { "basename": "SAFpof96.pdf", "url": "https://authors.library.caltech.edu/records/mcfft-p3h92/files/SAFpof96.pdf" }, "resource_type": "article", "pub_year": "1996", "author_list": "Saffman, P. G. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/dwr9b-td825", "eprint_id": 3601, "eprint_status": "archive", "datestamp": "2023-08-22 11:15:11", "lastmod": "2023-10-16 16:02:37", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Samtaney-Ravi", "name": { "family": "Samtaney", "given": "Ravi" }, "orcid": "0000-0002-4702-6473" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "On initial-value and self-similar solutions of the compressible Euler equations", "ispublished": "pub", "full_text_status": "public", "keywords": "COMPRESSIBLE FLOW; VORTEX FLOW; SHOCK WAVES; BOUNDARY\u2013VALUE PROBLEMS; NUMERICAL SOLUTION; EULER EQUATIONS; SELF\u2013SIMILIAR STATES; GAS DYNAMICS; FLUID\u2013FLUID INTERFACES", "note": "\u00a91996 American Institute of Physics. \n\nReceived 9 January 1996; accepted 20 May 1996. \n\nThis work was supported in part by AFOSR Grant No. F49620-93-1-0338. Useful discussions with P. Dimotakis, T. Hou, D. I. Meiron and J. Quirk are gratefully acknowledged. This research was performed in part using the CSCC parallel computer system operated by Caltech on behalf of the Concurrent Supercomputing Consortium.", "abstract": "We examine numerically the issue of convergence for initial-value solutions and similarity solutions of the compressible Euler equations in two dimensions in the presence of vortex sheets (slip lines). We consider the problem of a normal shock wave impacting an inclined density discontinuity in the presence of a solid boundary. Two solution techniques are examined: the first solves the Euler equations by a Godunov method as an initial-value problem and the second as a boundary value problem, after invoking self-similarity. Our results indicate nonconvergence of the initial-value calculation at fixed time, with increasing spatial-temporal resolution. The similarity solution appears to converge to the weak 'zero-temperature' solution of the Euler equations in the presence of the slip line. Some speculations on the geometric character of solutions of the initial-value problem are presented.", "date": "1996-10", "date_type": "published", "publication": "Physics of Fluids", "volume": "8", "number": "10", "publisher": "Physics of Fluids", "pagerange": "2650-2655", "id_number": "CaltechAUTHORS:SAMpof96", "issn": "1070-6631", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:SAMpof96", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.869050", "primary_object": { "basename": "SAMpof96.pdf", "url": "https://authors.library.caltech.edu/records/dwr9b-td825/files/SAMpof96.pdf" }, "resource_type": "article", "pub_year": "1996", "author_list": "Samtaney, Ravi and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/qt56y-cyg94", "eprint_id": 9052, "eprint_status": "archive", "datestamp": "2023-08-22 10:39:02", "lastmod": "2023-10-16 21:53:22", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Ardalan-K", "name": { "family": "Ardalan", "given": "K." } }, { "id": "Meiron-D-I", "name": { "family": "Meiron", "given": "D. I." }, "orcid": "0000-0003-0397-3775" }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Steady compressible vortex flows: the hollow-core vortex array", "ispublished": "pub", "full_text_status": "public", "note": "\u00a9 1995 Cambridge University Press. Reprinted with permission. \n\n(Received 28 December 1994 and in revised form 26 June 1995)", "abstract": "We examine the effects of compressiblity on the structure of a single row of hollowcore, constant-pressure vortices. The problem is formulated and solved in the hodograph plane. The transformation from the physical plane to the hodograph plane results in a linear problem that is solved numerically. The numerical solution is checked via a Rayleigh-Janzen expansion. It is observed that for an appropriate choice of the parameters M[infty infinity] = q[infty infinity]/c[infty infinity], and the speed ratio, a = q[infty infinity]/qv, where qv is the speed on the vortex boundary, transonic shock-free flow exists. Also, for a given fixed speed ratio, a, the vortices shrink in size and get closer as the Mach number at infinity, M[infty infinity], is increased. In the limit of an evacuated vortex core, we find that all such solutions exhibit cuspidal behaviour corresponding to the onset of limit lines.", "date": "1995-10-25", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "301", "publisher": "Cambridge University Press", "pagerange": "1-17", "id_number": "CaltechAUTHORS:ARDjfm95", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:ARDjfm95", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1017/S0022112095003764", "primary_object": { "basename": "ARDjfm95.pdf", "url": "https://authors.library.caltech.edu/records/qt56y-cyg94/files/ARDjfm95.pdf" }, "resource_type": "article", "pub_year": "1995", "author_list": "Ardalan, K.; Meiron, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/rf9vp-sz119", "eprint_id": 2398, "eprint_status": "archive", "datestamp": "2023-08-22 10:31:00", "lastmod": "2023-10-13 23:27:09", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Prochazka-A", "name": { "family": "Prochazka", "given": "A." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "On the two-dimensional stability of the axisymmetric Burgers vortex", "ispublished": "pub", "full_text_status": "public", "keywords": "VORTEX FLOW; INSTABILITY GROWTH RATES; NAVIER\u2013STOKES EQUATIONS; EIGENSTATES; REYNOLDS NUMBER; TURBULENT FLOW; TRANSITION FLOW", "note": "\u00a91995 American Institute of Physics. \n\n(Received 28 December 1994; accepted 16 February 1995) \n\nHelpful discussions with P. G. Saffman and D. Crowdy are gratefully acknowledged. This research was partial supported by National Science Foundation Grant No. CTS-9311811.", "abstract": "The stability of the axisymmetric Burgers vortex solution of the Navier\u2013Stokes equations to two-dimensional perturbations is studied numerically up to Reynolds numbers, R=Gamma/2pinu, of order 104. No unstable eigenmodes for azimuthal mode numbers n=1,..., 10 are found in this range of Reynolds numbers. Increasing the Reynolds number has a stabilizing effect on the vortex.", "date": "1995-07-01", "date_type": "published", "publication": "Physics of Fluids", "volume": "7", "number": "7", "publisher": "Physics of Fluids", "pagerange": "1788-1790", "id_number": "CaltechAUTHORS:PROpof95", "issn": "1070-6631", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:PROpof95", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.868495", "primary_object": { "basename": "PROpof95.pdf", "url": "https://authors.library.caltech.edu/records/rf9vp-sz119/files/PROpof95.pdf" }, "resource_type": "article", "pub_year": "1995", "author_list": "Prochazka, A. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/3v3qj-96r68", "eprint_id": 4674, "eprint_status": "archive", "datestamp": "2023-08-22 10:22:48", "lastmod": "2023-10-16 17:52:35", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Pressure spectra for vortex models of fine-scale homogeneous turbulence", "ispublished": "pub", "full_text_status": "public", "keywords": "TURBULENT FLOW; VORTEX FLOW; PRESSURE; CORRELATION FUNCTIONS; HOMOGENEITY; ENERGY SPECTRA; SCALING LAWS; VISCOUS FLOW", "note": "\u00a9 1995 American Institute of Physics. \n\n(Received 5 July 1994; accepted 1 November 1994) \n\nThe author wishes to thank P. G. Saffman for many useful discussions and for his comments on the original manuscript. Partial support under NSF Grant No. CTS-9311811 is gratefully acknowledged.\n\nPublished - PULpof95.pdf
", "abstract": "Pressure spectra at large wave numbers are calculated for Lundgren\u2013Townsend vortex models of the fine scales of homogeneous turbulence. Specific results are given for the Burgers vortex and also for the Lundgren-strained spiral vortex. For the latter case, it is found that the contribution to the shell-summed spectrum produced by the interaction between the axisymmetric and nonaxisymmetric components of the velocity field is proportional to k^\u20137/3 (k=||k|| is the modulus of the wave number) in agreement with Kolmogorov-type dimensional arguments. Numerical estimates of the dimensionless prefactors for this component are obtained in Kolmogorov scaling variables and comparisons are made with results from the Batchelor\u2013Kolmogorov theory, and with experimental measurement.", "date": "1995-04", "date_type": "published", "publication": "Physics of Fluids", "volume": "7", "number": "4", "publisher": "American Institute of Physics", "pagerange": "849-856", "id_number": "CaltechAUTHORS:PULpof95", "issn": "1070-6631", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:PULpof95", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF", "grant_number": "CTS-9311811" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.868608", "primary_object": { "basename": "PULpof95.pdf", "url": "https://authors.library.caltech.edu/records/3v3qj-96r68/files/PULpof95.pdf" }, "resource_type": "article", "pub_year": "1995", "author_list": "Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/m47kx-h8y53", "eprint_id": 107721, "eprint_status": "archive", "datestamp": "2023-08-22 10:14:59", "lastmod": "2024-01-15 21:21:09", "type": "book_section", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Saffman-P-G", "name": { "family": "Saffman", "given": "P. G." } } ] }, "title": "Vortex models of the fine scales of turbulence", "ispublished": "unpub", "full_text_status": "restricted", "keywords": "Probability Density Function; Isotropic Turbulence; Vorticity Field; Inertial Range; Vorticity Distribution", "note": "\u00a9 Springer-Verlag Berlin Heidelberg 1995. \n\nDIP was partially supported by NSF Grant CTS-9311811 and PGS was partially supported by the Department of Energy under Grant No. DE-FG03-89ER25073.", "abstract": "We survey the current status, prospects and problems of vortex models of the fine scales of turbulence. We begin with the attempt by Synge and Lin in the 1940's to calculate the longitudinal velocity correlation for isotropic tubulence using an ensemble of Hill's spherical vortices. A discussion of models based on the Burgers vortex is followed by a detailed description of the use of an ensemble of randomly oriented stretched spiral-vortex solutions of the Navier-Stokes equations to predict/postdict several small-scale properties of stationary homogeneous tubulence at large wavenumber. These include the spectra of various quantities and the one-point velocity gradient statistics.", "date": "1995", "date_type": "published", "publisher": "Springer", "place_of_pub": "Berlin", "pagerange": "61-74", "id_number": "CaltechAUTHORS:20210125-155052849", "isbn": "978-3-540-60486-0", "book_title": "Small-Scale Structures in Three-Dimensional Hydrodynamic and Magnetohydrodynamic Turbulence", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210125-155052849", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF", "grant_number": "CTS-9311811" }, { "agency": "Department of Energy (DOE)", "grant_number": "DE-FG03-89ER25073" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "contributors": { "items": [ { "id": "Meneguzzi-Maurice", "name": { "family": "Meneguzzi", "given": "Maurice" } }, { "id": "Pouquet-Annick", "name": { "family": "Pouquet", "given": "Annick" } }, { "id": "Sulem-Pierre-Louis", "name": { "family": "Sulem", "given": "Pierre-Louis" } } ] }, "doi": "10.1007/BFb0102400", "resource_type": "book_section", "pub_year": "1995", "author_list": "Pullin, D. I. and Saffman, P. G." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/wpg3x-9cj19", "eprint_id": 3268, "eprint_status": "archive", "datestamp": "2023-08-22 10:02:16", "lastmod": "2023-10-16 15:46:06", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Buntine-J-D", "name": { "family": "Buntine", "given": "James D." } }, { "id": "Saffman-P-G", "name": { "family": "Saffman", "given": "P. G." } } ] }, "title": "On the spectrum of a stretched spiral vortex", "ispublished": "pub", "full_text_status": "public", "keywords": "TURBULENT FLOW; VORTEX FLOW; ENERGY SPECTRA; ENERGY LOSSES; VISCOUS FLOW; SCALING LAWS; REYNOLDS NUMBER; INCOMPRESSIBLE FLOW; FINE STRUCTURE; CUT\u2013OFF", "note": "Copyright \u00a9 1994 American Institute of Physics \n\n(Received 2 December 1993; accepted 9 May 1994) \n\nThe authors wish to thank Professor D. W. Moore and Professor A. Leonard for helpful discussions. D.I.P. was partially supported by NSF Grant No. CTS-9311811 and P.G.S. was partially supported by the Department of Energy under Grant No. DE-FG03-89ER25073. We wish to thank Dr. Maurice Meneguzzi for providing unpublished data on velocity-derivative moments.", "abstract": "Corrections are found to the k^\u20135/3 spectrum of Lundgren [Phys. Fluids 25, 2193 (1982)] for a stretched spiral vortex model (a is the stretching strain rate and k the scalar wave number) of turbulent fine scales. These take the form of additional terms arising from the early time evolution, when the stretching of vortex lines is small. For the special case when the spiral takes the form of a rolled-up shear layer, it is shown that the composite spectrum is divergent, thus requiring the introduction of a finite early cutoff time tau1 in the time integral for the nonaxisymmetric contribution. The identity nuomega2 = 2nu[integral]0[infinity]k^2E(k)dk which gives the dissipation is then satisfied self-consistently. Direct numerical calculation of the energy spectrum from the approximate vorticity field for a special choice of spiral structure nevertheless indicates that the one-term k^\u20135/3-spectrum result is asymptotically valid in the inertial range provided atau1 is O(1) but that the numerically calculated dissipation spectrum appears to lie somewhere between an exp(\u2013B1k2) and an exp(\u2013B2k) form. It is also shown that the stretched, rolled-up shear-layer model predicts asymptotic shell-summed spectra of the energy dissipation and of the square of the vorticity, each asymptotically constant, with no power-law dependence, for k smaller than the Kolmogorov wave number.The corresponding one-dimensional spectra each show \u2013log(k1) behavior for small k1. The extension of the model given by Pullin and Saffman [Phys. Fluids A 5, 126 (1993)] is reformulated by the introduction of a long-time cutoff in the vortex lifetime and an additional requirement that the vortex structures be approximately space filling. This gives a reduction in the number of model free-parameters but introduces a dependence of the calculated Kolmogorov constant and skewness on the ratio of the initial vortex radius to the equivalent Burgers-vortex radius. A scaling for this ratio in terms of the Taylor microscale Reynolds number is proposed in which the stretching strain is assumed to be provided by the large scales with spatial coherence limited to the maximum stretched length of the structures. Postdictions of the fourth-order flatness factor and of higher moments of the longitudinal velocity gradient statistics are compared with numerical simulation.", "date": "1994-09-01", "date_type": "published", "publication": "Physics of Fluids", "volume": "6", "number": "9", "publisher": "Physics of Fluids", "pagerange": "3010-3027", "id_number": "CaltechAUTHORS:PULpof94b", "issn": "1070-6631", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:PULpof94b", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.868127", "primary_object": { "basename": "PULpof94b.pdf", "url": "https://authors.library.caltech.edu/records/wpg3x-9cj19/files/PULpof94b.pdf" }, "resource_type": "article", "pub_year": "1994", "author_list": "Pullin, D. I.; Buntine, James D.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/nsxbj-w4552", "eprint_id": 3266, "eprint_status": "archive", "datestamp": "2023-08-22 09:53:04", "lastmod": "2023-10-16 15:46:01", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Saffman-P-G", "name": { "family": "Saffman", "given": "P. G." } } ] }, "title": "Reynolds stresses and one-dimensional spectra for a vortex model of homogeneous anisotropic turbulence", "ispublished": "pub", "full_text_status": "public", "keywords": "TURBULENT FLOW; STRESSES; ANISOTROPY; ENERGY SPECTRA; VORTICES; KINETIC ENERGY; TENSORS; DISTRIBUTION FUNCTIONS; HOMOGENEITY; KINEMATICS", "note": "Copyright \u00a9 1994 American Institute of Physics \n\n(Received 24 June 1993; accepted 30 December 1993)\n\nDIP was partially supported by National Science Foundation Grant No. CTS-9311811 and PGS was partially supported by the Department of energy under Grant No. DE-FG03-89ER25073. The authors have benefited from discussions with Dr. A. Leonard.", "abstract": "Homogeneous anisotropic turbulence consisting of a collection of straight vortex structures is considered, each with a cylindrically unidirectional, but otherwise arbitrary, internal vorticity field. The orientations of the structures are given by a distribution P of appropriate Euler angles describing the transformation from laboratory to structure-fixed axes. One-dimensional spectra of the velocity components are calculated in terms of P, and the shell-summed energy spectrum. An exact kinematic relation is found in which volume-averaged Reynolds stresses are proportional to the turbulent kinetic energy of the vortex collection times a tensor moment of P. A class of large-eddy simulation models for nonhomogeneous turbulence is proposed based on application of the present results to the calculation of subgrid Reynolds stresses. These are illustrated by the development of a simplified model using a rapid-distortion-like approximation.", "date": "1994-05-01", "date_type": "published", "publication": "Physics of Fluids", "volume": "6", "number": "5", "publisher": "Physics of Fluids", "pagerange": "1787-1796", "id_number": "CaltechAUTHORS:PULpof94a", "issn": "1070-6631", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:PULpof94a", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.868240", "primary_object": { "basename": "PULpof94a.pdf", "url": "https://authors.library.caltech.edu/records/nsxbj-w4552/files/PULpof94a.pdf" }, "resource_type": "article", "pub_year": "1994", "author_list": "Pullin, D. I. and Saffman, P. G." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/gymat-36a42", "eprint_id": 3616, "eprint_status": "archive", "datestamp": "2023-08-22 09:46:37", "lastmod": "2023-10-16 16:03:29", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Saffman-P-G", "name": { "family": "Saffman", "given": "P. G." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Anisotropy of the Lundgren\u2013Townsend model of fine-scale turbulence", "ispublished": "pub", "full_text_status": "public", "keywords": "TURBULENT FLOW; ANISOTROPY; VORTICES; ENERGY SPECTRA; DISTRIBUTION FUNCTIONS; SCALING LAWS; VISCOUS FLOW; INCOMPRESSIBLE FLOW; HOMOGENEITY; VORTICITY", "note": "Copyright \u00a9 1994 American Institute of Physics. \n\nReceived 9 March 1993; accepted 3 June 1993. \n\nPGS wishes to thank the Center for Turbulence Research, Stanford University and NASA Ames, for hospitality while part of the work described here was carried out. He also wishes to thank the U.S. Department of Energy for partial support under Grant No. DE-FGO3-89ER25073.", "abstract": "The effect of a statistically anisotropic distribution of stretched vortices in the Lundgren-Townsend model of the fine-scale structure of homogeneous turbulence is considered. Lundgren's argument that anisotropy does not affect the three-dimensional energy spectrum is confirmed. Examples of velocity derivative moments and one-dimensional vorticity spectra are worked out for the case of an axisymmetric probability distribution. It is found that scaling of three-dimensional vorticity spectra may not be visible in the one-dimensional spectra.", "date": "1994-02-01", "date_type": "published", "publication": "Physics of Fluids", "volume": "6", "number": "2", "publisher": "Physics of Fluids", "pagerange": "802-807", "id_number": "CaltechAUTHORS:SAFpof94", "issn": "1070-6631", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:SAFpof94", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.868318", "primary_object": { "basename": "SAFpof94.pdf", "url": "https://authors.library.caltech.edu/records/gymat-36a42/files/SAFpof94.pdf" }, "resource_type": "article", "pub_year": "1994", "author_list": "Saffman, P. G. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/0npvp-a6f07", "eprint_id": 3262, "eprint_status": "archive", "datestamp": "2023-08-22 09:12:17", "lastmod": "2023-10-16 15:45:47", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Saffman-P-G", "name": { "family": "Saffman", "given": "P. G." } } ] }, "title": "On the Lundgren\u2013Townsend model of turbulent fine scales", "ispublished": "pub", "full_text_status": "public", "keywords": "TURBULENT FLOW; VELOCITY FIELDS; VORTICITY; VORTICES; HOMOGENEITY; ISOTROPY; CORRELATION FUNCTIONS; REYNOLDS NUMBER; NAVIER\u2013STOKES EQUATIONS; STRUCTURE FUNCTIONS; ENERGY SPECTRA", "note": "Copyright \u00a9 1993 American Institute of Physics \n\n(Received 14 May 1992; accepted 24 August 1992) \n\nThe authors wish to thank Dr. T. S. Lundgren, Dr. D. I. Meiron, and Professor D. W. Moore for valuable comments. Thanks are also due to Dr. Maurice Meneguzzi for providing unpublished data on velocity-derivative moments and to Dr. Robert Kerr for providing spectral data obtained from 1283 numerical simulations. One of us (PGS) thanks the Department of Energy for support under Grant No. DE-FG03-89ER 25073.", "abstract": "The strained-spiral vortex model of turbulent fines scales given by Lundgren [Phys. Fluids 25, 2193 (1982)] is used to calculate vorticity and velocity-derivative moments for homogeneous isotropic turbulence. A specific form of the relaxing spiral vortex is proposed modeled by a rolling-up vortex layer embedded in a background containing opposite signed vorticity and with zero total circulation at infinity. The numerical values of two dimensionless groups are fixed in order to give a Kolmogorov constant and skewness which are within the range of experiment. This gives the result that the ratio of the ensemble average hyperskewness S2p + 1[equivalent] ([partial-derivative]u/[partial-derivative]x)2p + 1/[([partial-derivative]u/[partial-derivative]x)2](2p + 1)/2 to the hyperflatness F2p[equivalent]([partial-derivative]u/[partial-derivative]x)2p/[([partial-derivative]u/[partial-derivative]x)2] p, p=2,3,..., is constant independent of Taylor\u2013Reynolds number Rlambda, as is the ratio of the 2pth moment of one component of the vorticity Omega2p[equivalent]omega2px/(omega2x)p to F2p. A cutoff in a relevant time integration is then used to eliminate vortex-sheet-induced divergences in the integrals corresponding to omega2px, p=2,3,..., and an assumption is made that the lateral scale of the spiral vortex in the model is the geometric mean of the Taylor and the Kolmogorov microscales. This gives Omega2p=Omega-hat 2pR lambda p/2 - 3/4, F2p=F-hat 2pR lambda p/2 - 3/4 and S2p + 1=S-hat 2p + 1R lambda p/2 - 3/4, p=2,3,..., with explicit calculation of the numbers Omega-hat 2p, F-hat 2p, and S-hat 2p + 1. The results of the model are compared with experimental compilation of Van Atta and Antonia [Phys. Fluids 23, 252 (1980)] for F4 and with the isotropic turbulence calculations of Kerr [J. Fluid Mech. 153, 31 (1985)] and of Vincent and Meneguzzi [J. Fluid Mech. 225, 1 (1991)].", "date": "1993-01-01", "date_type": "published", "publication": "Physics of Fluids A", "volume": "5", "number": "1", "publisher": "Physics of Fluids A", "pagerange": "126-145", "id_number": "CaltechAUTHORS:PULpofa93", "issn": "0899-8213", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:PULpofa93", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.858798", "primary_object": { "basename": "PULpofa93.pdf", "url": "https://authors.library.caltech.edu/records/0npvp-a6f07/files/PULpofa93.pdf" }, "resource_type": "article", "pub_year": "1993", "author_list": "Pullin, D. I. and Saffman, P. G." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/8qfqw-mf510", "eprint_id": 651, "eprint_status": "archive", "datestamp": "2023-08-22 08:41:03", "lastmod": "2023-10-13 21:54:48", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Contour Dynamics Methods", "ispublished": "pub", "full_text_status": "public", "keywords": "vorticity, vortex dynamics", "note": "\"Reprinted, with permission, from the Annual Review of Fluid Mechanics, Volume 24 copyright 1992 by Annual Reviews, www.annualreviews.org\"\n\nThe author wishes to thank Drs. G. R. Baker, D. I. Meiron, D. W. Moore, and M. J. Shelley for helpful discussions. Thanks are due especially to Dr. P. G. Saffman for providing valuable comments on a manuscript draft and to Dr. A. Rouhi for explaining the concepts of Hamiltonian dynamics as applied to vortex patches.", "abstract": "In an early paper on the stability of fluid layers with uniform vorticity Rayleigh (1880) remarks:\n\n\"... In such cases, the velocity curve is composed of portions of straight lines which meet each other at finite angles. This state of things may be supposed to be slightly disturbed by bending the surfaces of transition, and the determination of the subsequent motion depends upon that of the form of these surfaces. For co retains its constant value throughout each layer unchanged in the absence of friction, and by a well-known theorem the whole motion depends upon [omega].\"\n\nWe can now recognize this as essentially the principal of contour dynamics (CD), where [omega] is the uniform vorticity. The theorem referred to is the Biot-Savart law. Nearly a century later Zabusky et al (1979) presented numerical CD calculations of nonlinear vortex patch evolution. Subsequently, owing to its compact form conferring a deceptive simplicity, CD has become a widely used method for the investigation of two-dimensional rotational flow of an incompressible inviscid fluid. The aim of this article is to survey the development, technical details, and vortex-dynamic applications of the CD method in an effort to assess its impact on our understanding of the mechanics of rotational flow in two dimensions at ultrahigh Reynolds numbers. \n\nThe study of the dynamics of two- and three-dimensional vortex mechanics by computational methods has been an active research area for more than two decades. Quite apart from many practical applications in the aerodynamics of separated flows, the theoretical and numerical study of vortices in incompressible fluids has been stimulated by the idea that turbulent fluid motion may be viewed as comprising ensembles of more or less coherent laminar vortex structures that interact via relatively simple dynamics and by the appeal of the vorticity equation, which does not contain the fluid pressure. Two-dimensional vortex interactions have been perceived as supposedly relevant to the origins of coherent structures observed experimentally in mixing layers, jets, and wakes, and for models of large-scale atmospheric and oceanic turbulence. Interest has often focused on the limit of infinite Reynolds number, where in the absence of boundaries, the inviscid Euler equations are assumed to properly describe the flow dynamics. The numerous surveys of progress in the study of vorticity and the use of numerical methods applied to vortex mechanics include articles by Saffman & Baker (1979) and Saffman (1981) on inviscid vortex interactions and Aref (1983) on two-dimensional flows. Numerical methods have been surveyed by Chorin (1980), and Leonard (1980, 1985). Caflisch (1988) describes work on the mathematical aspects of the subject. Zabusky (1981), Aref (1983), and Melander et al (1987b) discuss various aspects of CD. The review of Dritschel (1989) gives emphasis to numerical issues in CD and to recent computations with contour surgery. \n\nThis article is confined to a discussion of vortices on a two-dimensional surface. We generally follow Saffman & Baker (1979) in matters of definition. In two dimensions a vortex sheet is a line of discontinuity in velocity while a vortex jump is a line of discontinuity in vorticity. We shall, however, use filament to denote a two-dimensional ribbon of vorticity surrounded by fluid with vorticity of different magnitude (which may be zero), rather than the more usual three-dimensional idea of a vortex tube. The ambiguity is unfortunate but is already in the literature. Additionally, a vortex patch is a finite, singly connected area of uniform vorticity while a vortex strip is an infinite strip of uniform vorticity with finite thickness, or equivalently, an infinite filament. Contour Dynamics will refer to the numerical solution of initial value problems for piecewise constant vorticity distributions by the Lagrangian method of calculating the evolution of the vorticity jumps. Such flows are often related to corresponding solutions of the Euler equations that are steady in some translating or rotating frame of reference. These solutions will be called vortex equilibria, and the numerical technique for computing their shapes based on CD is often referred to as contour statics. \n\nThe mathematical foundation for the study of vorticity was laid primarily by the well-known investigations of Helmholtz, Kelvin, J. J. Thomson, Love, and others. In our century, efforts to produce numerical simulations of flows governed by the Euler equations have utilized a variety of Eulerian, Lagrangian, and hybrid methods. Among the former are the class of spectral methods that now comprise the prevailing tool for large-scale two- and three-dimensional calculations (see Hussaini & Zang 1987). The Lagrangian methods for two-dimensional flows have been predominantly vortex tracking techniques based on the Helmholtz vorticity laws. The first initial value calculations were those of Rosenhead (193l) and Westwater (1935) who attempted to calculate vortex sheet evolution by the motion of O(10) point vortices. Subsequent efforts by Moore (1974) (see also Moore 1983, 1985) and others to produce more refined computations for vortex sheets have failed for reasons related to the tendency for initially smooth vortex sheet data to produce singularities (Moore 1979). Discrete vortex methods used to study the nonlinear dynamics of vortex patches and layers have included the evolution of assemblies of point vortices by direct summation (e.g. Acton 1976) and the cloud in cell method (Roberts & Christiansen 1972, Christiansen & Zabusky 1973, Aref & Siggia 1980, 1981). For reviews see Leonard (1980) and Aref (1983). These techniques have often been criticized for their lack of accuracy and numerical convergence and because they may be subject to grid scale dispersion. However, many qualitative vortex phenomena observed in nature and in experiments, such as amalgamation events and others still under active investigation (e.g. filamentation) were first simulated numerically with discrete vortices. The contour dynamics approach is attractive because it appears to allow direct access, at least for small times, to the inviscid dynamics for vorticity distributions smoother than those of either point vortices or vortex sheets, while at the same time enabling the mapping of the two-dimensional Euler equations to a one-dimensional Lagrangian form. \n\nIn Section 2 we discuss the formulation and numerical implementation of contour dynamics for the Euler equations in two dimensions. Section 3 is concerned with applications to isolated and multiple vortex systems and to vortex layers. An attempt is made to relate this work to calculations of the relevant vortex equilibria and to results obtained with other methods. Axisymmetric contour dynamics and the treatment of the multi-layer model of quasigeostrophic flows are described in Section 4 while Section 5 is devoted to a discussion of the tendency shown by vorticity jumps to undergo the strange and subtle phenomenon of filamentation.", "date": "1992-01-01", "date_type": "published", "publication": "Annual Review of Fluid Mechanics", "volume": "24", "publisher": "Annual Review of Fluid Mechanics", "pagerange": "89-115", "id_number": "CaltechAUTHORS:PULarfm92", "issn": "0066-4189", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:PULarfm92", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1146/annurev.fl.24.010192.000513", "primary_object": { "basename": "PULarfm92.pdf", "url": "https://authors.library.caltech.edu/records/8qfqw-mf510/files/PULarfm92.pdf" }, "resource_type": "article", "pub_year": "1992", "author_list": "Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/k9pfw-95531", "eprint_id": 2172, "eprint_status": "archive", "datestamp": "2023-08-22 08:24:13", "lastmod": "2023-10-13 23:14:51", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Mann-A-P", "name": { "family": "Mann", "given": "A. P." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Macrossan-M-N", "name": { "family": "Macrossan", "given": "M. N." } }, { "id": "Page-N-W", "name": { "family": "Page", "given": "N. W." } } ] }, "title": "Numerical modeling of dynamic powder compaction using the Kawakita equation of state", "ispublished": "pub", "full_text_status": "public", "keywords": "POWDERS; COMPACTING; HYDRODYNAMICS; EQUATIONS OF STATE; FLUID MECHANICS; COMPUTERIZED SIMULATION; SHOCK WAVES; FLUID FLOW", "note": "Copyright \u00a9 1991 American Institute of Physics. \n\nReceived 2 January 1991; accepted 18 June 1991. \n\nWe gratefully acknowledge support provided by the Australian Research Council under Grant No. A487 15757.", "abstract": "Dynamic powder compaction is analyzed using the assumption that the powder behaves, while it is being compacted, like a hydrodynamic fluid in which deviatoric stress and heat conduction effects can be ignored throughout the process. This enables techniques of computational fluid dynamics such the equilibrium flux method to be used as a modeling tool. The equation of state of the powder under compression is assumed to be a modified version of the Kawakita loading curve. Computer simulations using this model are performed for conditions matching as closely as possible with those from experiments by Page and Killen [Powder Metall. 30, 233 (1987)]. The numerical and experimental results are compared and a surprising degree of qualitative agreement is observed.", "date": "1991-09-15", "date_type": "published", "publication": "Journal of Applied Physics", "volume": "70", "number": "6", "publisher": "Journal of Applied Physics", "pagerange": "3281-3290", "id_number": "CaltechAUTHORS:MANjap91", "issn": "0021-8979", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:MANjap91", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.349262", "primary_object": { "basename": "MANjap91.pdf", "url": "https://authors.library.caltech.edu/records/k9pfw-95531/files/MANjap91.pdf" }, "resource_type": "article", "pub_year": "1991", "author_list": "Mann, A. P.; Pullin, D. I.; et el." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/5a9j2-d7k59", "eprint_id": 10005, "eprint_status": "archive", "datestamp": "2023-08-22 08:12:14", "lastmod": "2023-10-16 22:37:10", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Moore-D-W", "name": { "family": "Moore", "given": "D. W." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "The effect of heat addition on slightly compressible flow: The example of vortex pair motion", "ispublished": "pub", "full_text_status": "public", "note": "\u00a9 1991 American Institute of Physics. \n\nReceived 17 April 1990; accepted 20 March 1991. \n\nWe are grateful to Dr. E.G. Broadbent and Dr. J.E. Broadwell for helpful discussion and for comments on the manuscript. \n\nThis work was supported by a Science and Engineering Research Council grant.\n\nPublished - MOOpofa91.pdf
", "abstract": "The effect of a point heat source on the two-dimensional irrotational flow of a slightly compressible nonviscous and nondiffusive fluid is studied. Heat is added at a constant rate and with a prescribed spatial distribution. The Mach number M is assumed small and the governing equations are solved to order M^2 by a generalization of the Rayleigh\u2013Janzen expansion. The interaction between entropy variations produced by the heat source and the pressure field generates a wake consisting of a vortex sheet and a dipole sheet extending downstream of the heat source, and this in turn perturbs the flow at order M^2. A general result is that if heat is added where the gas is compressed by the flow, the impulse directed against the free stream is increased and vice versa. Cross-stream impulse is produced if the heat source is not on the axis of symmetry (if any) of the flow. This would result in a lifting force if a cylinder is providing the perturbation to the free stream. When heat is added on the downstream dividing streamline of a symmetrical flow the order M^2 velocity field at infinity is that due to an apparent mass source and it is shown that the required flux of mass and momentum is supplied from infinity via the wake. Detailed calculations are performed for the case of the self-propagation of a symmetrical vortex pair, where heat is added downstream of the rearward stagnation point. The resultant increase in the pair impulse is shown to lead to a slow increase in the vortex pair separation.", "date": "1991-08", "date_type": "published", "publication": "Physics of Fluids A", "volume": "3", "number": "8", "publisher": "American Institute of Physics", "pagerange": "1907-1914", "id_number": "CaltechAUTHORS:MOOpofa91", "issn": "0899-8213", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:MOOpofa91", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Science and Engineering Research Council (SERC)" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.857920", "primary_object": { "basename": "MOOpofa91.pdf", "url": "https://authors.library.caltech.edu/records/5a9j2-d7k59/files/MOOpofa91.pdf" }, "resource_type": "article", "pub_year": "1991", "author_list": "Moore, D. W. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/0bmba-vnn02", "eprint_id": 52960, "eprint_status": "archive", "datestamp": "2023-08-19 23:49:22", "lastmod": "2023-10-18 21:48:50", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Saffman-P-G", "name": { "family": "Saffman", "given": "P. G." } } ] }, "title": "Long-Time Symplectic Integration: The Example of Four-Vortex Motion", "ispublished": "pub", "full_text_status": "restricted", "note": "\u00a9 1991 The Royal Society.\n\nReceived 23 July 1990; accepted 9 October 1990.\n\nThe authors are grateful for helpful discussions with Dr S. J. Cowley, Dr H. B. Keller, Dr J.\nLorenz, Dr D. I. Meiron, Professor D. W. Moore, Dr E. Van der Velde and especially Dr A. Rouhi.", "abstract": "Detailed comparisons are made between long-time numerical integration of the motion of four identical point vortices obtained using both a fourth-order symplectic integration method of the implicit Runge-Kutta type and a standard fourth-order explicit Runge-Kutta scheme. We utilize the reduced hamiltonian formulation of the four-vortex problem due to Aref & Pomphrey. Initial conditions which give both fully chaotic and also quasi-periodic motions are considered over integration times of order 10^6-10^7 times the characteristic time scale of the evolution. The convergence, as the integration time step is decreased, of the Poincare section is investigated. When smoothness of the section compared to the converged image, and the fractional change in the hamiltonian H are used as diagnostic indicators, it is found that the symplectic scheme gives substantially superior performance over the explicit scheme, and exhibits only an apparent qualitative degrading in results up to integration time steps of order the minimum timescale of the evolution. It is concluded that this performance derives from the symplectic rather than the implicit character of the method.", "date": "1991-03-08", "date_type": "published", "publication": "Proceedings of the Royal Society of London. Series A, Mathematical, Physical and Engineering Sciences", "volume": "432", "number": "1886", "publisher": "Royal Society", "pagerange": "481-494", "id_number": "CaltechAUTHORS:20141217-110551867", "issn": "0962-8444", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141217-110551867", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "resource_type": "article", "pub_year": "1991", "author_list": "Pullin, D. I. and Saffman, P. G." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/h2652-ne231", "eprint_id": 3264, "eprint_status": "archive", "datestamp": "2023-08-22 07:39:13", "lastmod": "2023-10-16 15:45:56", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Moore-D-W", "name": { "family": "Moore", "given": "D. W." } } ] }, "title": "Remark on a result of D. Dritschel", "ispublished": "pub", "full_text_status": "public", "keywords": "DISTURBANCES; SYMMETRY; AMPLITUDES; NUMERICAL SOLUTION; FILAMENTATION INSTABILITIES; LAMINAR FLOW; VORTICES; IDEAL FLOW; INCOMPRESSIBLE FLOW", "note": "Copyright \u00a9 1990 American Institute of Physics \n\n(Received 23 August 1989; accepted 5 February 1990) \n\nThis work was made possible by a Science and Engineering Research Council grant.", "abstract": "A hypothesis put forward by D. Dritschel [J. Fluid Mech. 94, 511 (1988)], namely that an isolated symmetrical disturbance on a uniform vortex patch will filament in time proportional to the inverse square of the disturbance amplitude, is subject to independent testing using a nonintrusive numerical method. The hypothesis that the trend is maintained to substantially smaller amplitudes than were originally considered by Dritschel is both supported and verified. The results may be interpreted as providing limited evidence that contour smoothness is maintained in filamentation and that corner formation does not occur up to the time of wave overturning.", "date": "1990-06-01", "date_type": "published", "publication": "Physics of Fluids A", "volume": "2", "number": "6", "publisher": "Physics of Fluids A", "pagerange": "1039-1041", "id_number": "CaltechAUTHORS:PULpofa90", "issn": "0899-8213", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:PULpofa90", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.857641", "primary_object": { "basename": "PULpofa90.pdf", "url": "https://authors.library.caltech.edu/records/h2652-ne231/files/PULpofa90.pdf" }, "resource_type": "article", "pub_year": "1990", "author_list": "Pullin, D. I. and Moore, D. W." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/s78cx-5rj12", "eprint_id": 91104, "eprint_status": "archive", "datestamp": "2023-08-19 21:25:23", "lastmod": "2023-10-19 22:09:31", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Jacobs-P-A", "name": { "family": "Jacobs", "given": "P. A." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Multiple-contour-dynamic simulation of eddy scales in the plane shear layer", "ispublished": "pub", "full_text_status": "restricted", "note": "\u00a9 1989 Cambridge University Press. \n\n(Received 8 December 1987 and in revised form 23 June 1988) \n\nPart of this work was supported by the Australian Research Grants Scheme under grant No. F8315013 I. P. A. J. was supported by an Australian Commonwealth Postgraduate Research Award. Computing time was given by the CSIRO. on their Cyber 205.", "abstract": "The method of contour dynamics (CD) is applied to several inviscid prototype flows typical of the motions found in the transition region of the free shear layer. Examples of the interaction between the fundamental streamwise-layer perturbation and its first subharmonic are presented that illustrate the events of pairing and tearing of two rolled-up cores and also the coalescence of three rolled-up cores. The present simulations of the temporally unstable two-dimensional layer, at effectively infinite Reynolds number, support the hypothesis that the dynamics of the large-scale roll-up is only weakly dependent on Reynolds number. However, we find fine-scale structure that is not apparent in previous simulations at moderate Reynolds number. Spiral filaments of rotational fluid wrap around the rolled-up vortex cores producing 'spiky' vorticity distributions together with the entanglement of large quantities of irrotational fluid into the layer. Simulations proceeded only until the first such event because we were unable to resolve the fine detail generated subsequently. The inclusion of prescribed vortex stretching parallel to the vortex lines is found to accelerate the initial roll-up and to enhance the production of spiral vortex filaments. In the fundamental-subharmonic interaction, vortex stretching slows but does not prevent pairing.", "date": "1989-02", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "199", "publisher": "Cambridge University Press", "pagerange": "89-124", "id_number": "CaltechAUTHORS:20181120-153100596", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181120-153100596", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Australian Research Grants Committee", "grant_number": "F 8315031 I" }, { "agency": "Australian Commonwealth Postgraduate Research Award" } ] }, "doi": "10.1017/s0022112089000303", "resource_type": "article", "pub_year": "1989", "author_list": "Jacobs, P. A. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/gfw1m-pxz41", "eprint_id": 4671, "eprint_status": "archive", "datestamp": "2023-08-22 06:07:22", "lastmod": "2023-10-16 17:52:28", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Grimshaw-R-H-J", "name": { "family": "Grimshaw", "given": "R. H. J." } } ] }, "title": "Finite-amplitude solitary waves at the interface between two homogeneous fluids", "ispublished": "pub", "full_text_status": "public", "keywords": "SOLITONS; HYDRODYNAMICS; NUMERICAL SOLUTION; WAVE PROPAGATION; VORTICES; VORTEX FLOW; FLUID\u2013FLUID INTERFACES; DENSITY; BOUSSINESQ EQUATIONS", "note": "Copyright \u00a9 1988 American Institute of Physics \n\n(Received 30 November 1987; accepted 9 August 1988) \n\nThe contribution of D. I. Pullin to this work was supported by the Australian Research Grants Scheme under Drant No. A48315031.", "abstract": "Numerical solutions are presented for finite-amplitude interfacial waves. Only symmetric waves are calculated. Two cases are considered. In the first case the waves are free-surface solitary waves propagating on a basic flow with uniform vorticity. Large-amplitude waves of extreme form are calculated for a range of values of the basic vorticity. In the second case the waves are propagating on the interface between two homogeneous fluids of different densities, which are otherwise at rest. Again large-amplitude waves of extreme form are calculated for a range of values of the basic density ratio. In particular, in the Boussinesq limit when the density ratio is nearly unity, solitary waves of apparently unlimited amplitude can be found.", "date": "1988-12-01", "date_type": "published", "publication": "Physics of Fluids", "volume": "31", "number": "12", "publisher": "Physics of Fluids", "pagerange": "3550-3559", "id_number": "CaltechAUTHORS:PULpof88", "issn": "0031-9171", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:PULpof88", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.866922", "primary_object": { "basename": "PULpof88.pdf", "url": "https://authors.library.caltech.edu/records/gfw1m-pxz41/files/PULpof88.pdf" }, "resource_type": "article", "pub_year": "1988", "author_list": "Pullin, D. I. and Grimshaw, R. H. J." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/64bpa-tmk32", "eprint_id": 91103, "eprint_status": "archive", "datestamp": "2023-08-19 19:59:35", "lastmod": "2023-10-19 22:09:24", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Moore-D-W", "name": { "family": "Moore", "given": "D. W." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "The compressible vortex pair", "ispublished": "pub", "full_text_status": "restricted", "note": "\u00a9 1987 Cambridge University Press. \n\n(Received 6 February 1987) \n\nWe are grateful to Professor Barsony-Nagy for permission to use his results prior to their publication.", "abstract": "We consider the steady self-propagation with respect to the fluid at infinity of two equal symmetrically shaped vortices in a compressible fluid. Each vortex core is modelled by a region of stagnant constant-pressure fluid bounded by closed constant-pressure, constant-speed streamlines of unknown shape. The external flow is assumed to be irrotational inviscid isentropic flow of a perfect gas. The flow is therefore shock free but may be locally supersonic. The nonlinear free-boundary problem for the vortex-pair flow is formulated in the hodograph plane of compressible-flow theory, and a numerical solution method based on finite differences is described. Specific results are presented for a range of parameters which control the flow, namely the Mach number of the pair translational motion and the fluid speed on each vortex bounding streamline. Perturbation-theory predictions are developed, valid for vortices of small core radius when the pair Mach number is much less than unity. These are in good agreement with the hodograph-plane calculations. The numerical and the perturbation-theory results together confirm the recently discovered (Barsony-Nagy, Er-El & Yungster 1987) existence of continuous shock-free transonic compressible flows with embedded vortices. For the vortex-pair geometry studied, solution branches corresponding to physically acceptable flows that could be calculated using the present hodograph-plane numerical method were found to be terminated when either the flow on the streamline of symmetry separating the vortiqes tends to become superonic or when limiting lines appear in the hodograph plane giving a locally multivalued mapping to the physical plane.", "date": "1987-12", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "185", "publisher": "Cambridge University Press", "pagerange": "171-204", "id_number": "CaltechAUTHORS:20181120-153100516", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181120-153100516", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "doi": "10.1017/s0022112087003136", "resource_type": "article", "pub_year": "1987", "author_list": "Moore, D. W. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/49fme-nma02", "eprint_id": 91102, "eprint_status": "archive", "datestamp": "2023-08-19 18:56:31", "lastmod": "2023-10-19 22:09:22", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Grimshaw-R-H-J", "name": { "family": "Grimshaw", "given": "R. H. J." } } ] }, "title": "Stability of finite-amplitude interfacial waves. Part 3. The effect of basic current shear for one-dimensional instabilities", "ispublished": "pub", "full_text_status": "restricted", "note": "\u00a9 1986 Cambridge University Press. \n\n(Received 4 June 1985 and in revised form 13 February 1986) \n\nThe contribution of D. I. Pullin to the present work was supported by the Australian Research Grants Scheme under Grant no. F8315031 R.", "abstract": "We consider the linearized stability of interfacial progressive waves in a two-layer inviscid fluid, for the case when there is a basic current shear in either, or both, of the fluids. For this configuration the basic wave has been calculated by Pullin & Grimshaw (1983b). Our results here are mainly restricted to two-space-dimensional instabilities (i.e. one-dimensional in the propagation space), and are obtained both analytically and numerically. The analytical results are for the long-wavelength modulational instability of small-amplitude waves. The numerical results are restricted to the case when the lower fluid is infinitely deep, and for the Boussinesq approximation. They are obtained by solving the linearized stability problem with truncated Fourier series, and solving the resulting eigenvalue problem for the growth rate. For small values of the basic current shear, and for small or moderate basic wave amplitude, the instabilities are determined by a set of low-order resonances; for larger basic wave amplitude, these are dominated by the onset of a local wave-induced Kelvin\u2013Helmholtz instability. For larger values of the basic current shear, this interpretation is modified owing to the appearance of a number of new effects.", "date": "1986-11", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "172", "publisher": "Cambridge University Press", "pagerange": "277-306", "id_number": "CaltechAUTHORS:20181120-153100421", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181120-153100421", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Australian Research Grants Committee", "grant_number": "F 8315031 R" } ] }, "doi": "10.1017/s002211208600174x", "resource_type": "article", "pub_year": "1986", "author_list": "Pullin, D. I. and Grimshaw, R. H. J." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/580wz-kv985", "eprint_id": 91100, "eprint_status": "archive", "datestamp": "2023-08-19 18:52:57", "lastmod": "2023-10-19 22:09:06", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Jacobs-P-A", "name": { "family": "Jacobs", "given": "P. A." } } ] }, "title": "Inviscid evolution of stretched vortex arrays", "ispublished": "pub", "full_text_status": "restricted", "note": "\u00a9 1986 Cambridge University Press. \n\n(Received 4 June 1985 and in revised form 25 March 1986) \n\nThis work was supported by the Australian Research Grants Scheme under Grant No. F8315031 I.", "abstract": "The nonlinear evolution of an array of pairs of inviscid counter-rotating vortices, subjected to an applied stretching strain field, has been studied numerically using the contour-dynamics method. The array configuration is effectively the Corcos-Lin model of streamwise vortices in the braid region of a nominally two-dimensional mixing layer. For each individual vortex the simulations elucidate the strong interaction between the vortex self-induction, the vorticity amplification of the stretching strain, and the local in-plane strain applied by all other members of the array. When the initial vorticity distribution is modelled by a non-uniform piece-wise-constant vorticity field defined over a nested set of non-intersecting contours, the dynamical evolution reveals fine structure consisting of strong vortex roll-up accompanied by trailing, filament-like spiral vortex sheets, and the presence of tertiary instabilities. It is shown by a particular example that these features are largely absent in an equivalent computation in which array members are modelled by the commonly used uniform-vortex approximation.", "date": "1986-10", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "171", "publisher": "Cambridge University Press", "pagerange": "377-406", "id_number": "CaltechAUTHORS:20181120-153100192", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181120-153100192", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Australian Research Grants Committee", "grant_number": "F 8315031 I" } ] }, "doi": "10.1017/s0022112086001490", "resource_type": "article", "pub_year": "1986", "author_list": "Pullin, D. I. and Jacobs, P. A." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/1f7d2-d0r70", "eprint_id": 10316, "eprint_status": "archive", "datestamp": "2023-08-22 04:58:13", "lastmod": "2023-10-16 22:47:54", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Grimshaw-R-H-J", "name": { "family": "Grimshaw", "given": "R. H. J." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Extreme interfacial waves", "ispublished": "pub", "full_text_status": "public", "keywords": "NUMERICAL SOLUTION, INTERFACES, WAVES, FLUIDS, DENSITY, BOUSSINESQ EQUATIONS, VORTEX FLOW, SYMMETRY", "note": "Copyright \u00a9 1986 American Institute of Physics. \n\nReceived 3 January 1986; accepted 13 June 1986.", "abstract": "Numerical solutions are presented for large-amplitude interfacial waves of extreme form on the interface between two fluids of different densities in the Boussinesq approximation. The flow in the lower fluid is irrotational, but the upper fluid may have constant, nonzero vorticity. Only symmetric waves are calculated. The results suggest limiting wave profiles for which separate portions of the interface touch, forming stagnant zones of one fluid imbedded in the other fluid.", "date": "1986-09-01", "date_type": "published", "publication": "Physics of Fluids", "volume": "29", "number": "9", "publisher": "Physics of Fluids", "pagerange": "2802-2807", "id_number": "CaltechAUTHORS:GRIpof86", "issn": "0031-9171", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:GRIpof86", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.865477", "primary_object": { "basename": "GRIpof86.pdf", "url": "https://authors.library.caltech.edu/records/1f7d2-d0r70/files/GRIpof86.pdf" }, "resource_type": "article", "pub_year": "1986", "author_list": "Grimshaw, R. H. J. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/vg9wx-tcr32", "eprint_id": 91101, "eprint_status": "archive", "datestamp": "2023-08-19 18:04:51", "lastmod": "2023-10-19 22:09:16", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Grimshaw-R-H-J", "name": { "family": "Grimshaw", "given": "R. H. J." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Stability of finite-amplitude interfacial waves. Part 1. Modulational instability for small-amplitude waves", "ispublished": "pub", "full_text_status": "restricted", "note": "\u00a9 1985 Cambridge University Press. \n\n(Received 2 April 1984 and in revised form 7 November 1984)", "abstract": "In two previous papers (Pullin & Grimshaw 1983a, b) we studied the wave profile and other properties of finite-amplitude interfacial progressive waves in a two-layer fluid. In this and the following paper (Pullin & Grimshaw 1985) we discuss the stability of these waves to small perturbations. In this paper we obtain anatytical results for the long-wavelength modulational instability of small-amplitude waves. Using a multiscale expansion, we obtain a nonlinear Schr\u00f6dinger equation coupled to a wave-induced mean-flow equation to describe slowly modulated waves. From these coupled equations we determine the stability of a plane progressive wave. Our results are expressed by determining the instability bands in the (p, q)-plane, where (p, q) is the modulation wavenumber, and are obtained for a range of values of basic density ratio and undisturbed layer depths.", "date": "1985-11", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "160", "publisher": "Cambridge University Press", "pagerange": "297-315", "id_number": "CaltechAUTHORS:20181120-153100310", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181120-153100310", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "doi": "10.1017/s0022112085003494", "resource_type": "article", "pub_year": "1985", "author_list": "Grimshaw, R. H. J. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/gcegt-k7d50", "eprint_id": 91099, "eprint_status": "archive", "datestamp": "2023-08-19 18:04:44", "lastmod": "2023-10-19 22:09:03", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Grimshaw-R-H-J", "name": { "family": "Grimshaw", "given": "R. H. J." } } ] }, "title": "Stability of finite-amplitude interfacial waves. Part 2. Numerical results", "ispublished": "pub", "full_text_status": "restricted", "note": "\u00a9 1985 Cambridge University Press. \n\n(Received 2 April 1984 and in revised form 7 November 1984)", "abstract": "In the preceding paper (Grimshaw & Pullin 1985) we discussed the long-wavelength modulational instability of interfacial progressive waves in a two-layer fluid. In this paper we complement our analytical results by numerical results for the linearized stability of finite-amplitude waves. We restrict attention to the case when the lower layer is infinitely deep, and use the Boussinesq approximation. For this case the basic wave profile has been calculated by Pullin & Grimshaw (1983a, b). The linearized stability problem for perturbations to the basic wave is solved numerically by seeking solutions in the form of truncated Fourier series, and solving the resulting eigenvalue problem for the growth rate as a function of the perturbation wavenumber. For small or moderate basic wave amplitudes we show that the instabilities are determined by a set of low-order resonances. The lowest resonance, which contains the modulational instability, is found to be dominant for all cases considered. For higher wave amplitudes, the resonance instabilities are swamped by a local wave-induced Kelvin\u2013Helmholtz instability.", "date": "1985-11", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "160", "publisher": "Cambridge University Press", "pagerange": "317-336", "id_number": "CaltechAUTHORS:20181120-153100107", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181120-153100107", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "doi": "10.1017/s0022112085003500", "resource_type": "article", "pub_year": "1985", "author_list": "Pullin, D. I. and Grimshaw, R. H. J." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/pnwbj-7tn68", "eprint_id": 12789, "eprint_status": "archive", "datestamp": "2023-08-19 17:48:04", "lastmod": "2023-10-17 20:55:30", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Jacobs-P-A", "name": { "family": "Jacobs", "given": "P. A." } }, { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Coalescence of stretching vortices", "ispublished": "pub", "full_text_status": "public", "keywords": "NUMERICAL ANALYSIS, THREE\u2212DIMENSIONAL CALCULATIONS, COALESCENCE, VORTICES, CYLINDRICAL CONFIGURATION, SYMMETRY, INITIAL CONDITIONS, VORTEX FLOW, FLOW MODELS", "note": "Copyright \u00a9 1985 American Institute of Physics. \n\nReceived 13 August 1984; accepted 29 November 1984. \n\nThis work was supported by the Australian Research Grants Scheme under Grant No. F 8315031 I.\n\nPublished - JACpof85.pdf
", "abstract": "The contour dynamics numerical technique is used to study the coalescence of two equal uniform vortices in the presence of an externally applied stretching strain field. Plane three-dimensional stretching is found to substantially inhibit vortex coalescence when the plane of the vortex axes is initially perpendicular to the plane of the straining motion. This behavior is interpreted qualitatively in terms of a purely two-dimensional flow fully equivalent to the stretching configuration.", "date": "1985-06", "date_type": "published", "publication": "Physics of Fluids", "volume": "28", "number": "6", "publisher": "American Institute of Physics", "pagerange": "1619-1625", "id_number": "CaltechAUTHORS:JACpof85", "issn": "0031-9171", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:JACpof85", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Australian Research Grants Committee", "grant_number": "F 8315031 I" } ] }, "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.864953", "primary_object": { "basename": "JACpof85.pdf", "url": "https://authors.library.caltech.edu/records/pnwbj-7tn68/files/JACpof85.pdf" }, "resource_type": "article", "pub_year": "1985", "author_list": "Jacobs, P. A. and Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/7z862-ghm08", "eprint_id": 4673, "eprint_status": "archive", "datestamp": "2023-08-22 03:32:57", "lastmod": "2023-10-16 17:52:33", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Grimshaw-R-H-J", "name": { "family": "Grimshaw", "given": "R. H. J." } } ] }, "title": "Interfacial progressive gravity waves in a two-layer shear flow", "ispublished": "pub", "full_text_status": "public", "keywords": "interfaces; gravity waves; nonlinear problems; boussinesq equations; fluids; layers; shear; vortices; density; velocity; fluid flow; numerical solution; integral equations; shape; stratification; flow models", "note": "Copyright \u00a9 1983 American Institute of Physics \n\n(Received 15 November 1982; accepted 23 March 1983)", "abstract": "Nonlinear interfacial gravity waves in a two-layer Boussinesq fluid are studied. In a previous paper, nonlinear waves on a vortex sheet separating two layers, each of constant density and velocity were considered. In the present paper the basic flow model consists of a constant vorticity upper layer bounded by a rigid surface and an irrotational lower layer of infinite depth with continuity of the unperturbed velocity at the density interface. Numerical solutions obtained from an exact formulation in terms of a complex-valued integral equation for the shape and local vortex-sheet strength of the wave profile are compared with results from a second-order Stokes expansion. It is found that the wave of maximum amplitude displays different geometrical features depending on the unperturbed flow parameters. These include waves containing an S-shaped section, waves with cusped crests and surface-constrained waves with long flat crests. Wave integral properties calculated, including the flux of momentum and energy in the wave propagation direction, showed monotonic variation with increasing wave amplitude.", "date": "1983-07-01", "date_type": "published", "publication": "Physics of Fluids", "volume": "26", "number": "7", "publisher": "Physics of Fluids", "pagerange": "1731-1739", "id_number": "CaltechAUTHORS:PULpof83b", "issn": "0031-9171", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:PULpof83b", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.864372", "primary_object": { "basename": "PULpof83b.pdf", "url": "https://authors.library.caltech.edu/records/7z862-ghm08/files/PULpof83b.pdf" }, "resource_type": "article", "pub_year": "1983", "author_list": "Pullin, D. I. and Grimshaw, R. H. J." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/rhpqs-gyt60", "eprint_id": 4672, "eprint_status": "archive", "datestamp": "2023-08-22 03:27:38", "lastmod": "2023-10-16 17:52:30", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Grimshaw-R-H-J", "name": { "family": "Grimshaw", "given": "R. H. J." } } ] }, "title": "Nonlinear interfacial progressive waves near a boundary in a Boussinesq fluid", "ispublished": "pub", "full_text_status": "public", "keywords": "nonlinear problems; ideal flow; interfaces; fluids; surface waves; bound state; boundary layers; integral equations; numerical solution; shape", "note": "Copyright \u00a9 1983 American Institute of Physics \n\n(Received 4 May 1982; accepted 11 September 1982)", "abstract": "The behavior of nonlinear progressive waves at the interface between two inviscid fluids in the presence of an upper free boundary is studied as a model of waves on the thermocline. A set of relationships between the integral properties of bounded waves in a general two-fluid model is first developed and the Stokes expansion to third order is derived. The exact free boundary problem for the wave profile is then formulated within the Boussinesq approximation as a nonlinear integral equation, which is solved numerically using two different numerical methods. For finite velocity difference across the two-fluid interface bifurcation of solutions into upper and lower branch wave profiles with quite different properties is obtained. Numerically calculated wave shapes and integral properties show good agreement with third-order Stokes expansion predictions in the weakly nonlinear regime for waves which are not too long. Very long waves were found to exhibit distinct solitary wave-like features.", "date": "1983-04-01", "date_type": "published", "publication": "Physics of Fluids", "volume": "26", "number": "4", "publisher": "Physics of Fluids", "pagerange": "897-905", "id_number": "CaltechAUTHORS:PULpof83a", "issn": "0031-9171", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:PULpof83a", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.864239", "primary_object": { "basename": "PULpof83a.pdf", "url": "https://authors.library.caltech.edu/records/rhpqs-gyt60/files/PULpof83a.pdf" }, "resource_type": "article", "pub_year": "1983", "author_list": "Pullin, D. I. and Grimshaw, R. H. J." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/m8fe7-ye380", "eprint_id": 91098, "eprint_status": "archive", "datestamp": "2023-08-19 15:08:03", "lastmod": "2023-10-19 22:08:56", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Numerical studies of surface-tension effects in nonlinear Kelvin\u2013Helmholtz and Rayleigh\u2013Taylor instability", "ispublished": "pub", "full_text_status": "restricted", "note": "\u00a9 1982 Cambridge University Press. \n\n(Received 5 January 1981 and in revised form 9 November 1981) \n\nThe author would like to thank Cr J. Y. Holyer of Topexpress Limited, who kindly supplied him with detailed solutions for interfacial gravity waves, and also Dr R. H. J. Grimshaw of the Department of Mathematics, University of Melbourne, who provided useful comments on the original manuscript.", "abstract": "We consider the behaviour of an interface between two immiscible inviscid incompressible fluids of different density moving under the action of gravity, inertial and interfacial tension forces. A vortex-sheet model of the exact nonlinear two-dimensional motion of this interface is formulated which includes expressions for an appropriate set of integral invariants. A numerical method for solving the vortex-sheet initial-value equations is developed, and is used to study the nonlinear growth of finite-amplitude normal modes for both Kelvin-Helmholtz and Rayleigh-Taylor instability. In the absence of an interfacial or surface-tension term in the integral-differential equation that describes the evolution of the circulation distribution on the vortex sheet, it is found that chaotic motion of, or the appearance of curvature singularities in, the discretized interface profiles prevent the simulations from proceeding to the late-time highly nonlinear phase of the motion. This unphysical behaviour is interpreted as a numerical manifestation of possible ill-posedness in the initial-value equations equivalent to the infinite growth rate of infinitesimal-wavelength disturbances in the linearized stability theory. The inclusion of an interfacial tension term in the circulation equation (which stabilizes linearized short-wavelength perturbations) was found to smooth profile irregularities but only for finite times. While coherent interfacial motion could then be followed well into the nonlinear regime for both the Kelvin-Helmholtz and Rayleigh-Taylor modes, locally irregular behaviour eventually reappeared and resisted subsequent attempts at numerical smoothing or suppression. Although several numerical and/or physical mechanisms are discussed that might produce irregular behaviour of the discretized interface in the presence of an interfacial-tension term, the basic cause of this instability remains unknown. The final description of the nonlinear interface motion thus awaits further research.", "date": "1982-06", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "119", "publisher": "Cambridge University Press", "pagerange": "507-532", "id_number": "CaltechAUTHORS:20181120-153100022", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181120-153100022", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "doi": "10.1017/s0022112082001463", "resource_type": "article", "pub_year": "1982", "author_list": "Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/rj00r-ykj68", "eprint_id": 91097, "eprint_status": "archive", "datestamp": "2023-08-19 14:16:39", "lastmod": "2023-10-19 22:08:47", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "The nonlinear behaviour of a constant vorticity layer at a wall", "ispublished": "pub", "full_text_status": "restricted", "note": "\u00a9 1981 Cambridge University Press. \n\n(Received 25 March 1980 and in revised form 21 October 1980)", "abstract": "The so-called 'water-bag' method is used to study the behaviour of a two-dimensional inviscid layer of constant vorticity \u03c9 and of mean thickness \u03b4 adjacent to a wall with slip at the wall. A nonlinear initial-value equation is derived which describes the motion of the material interface separating the rotational fluid within the layer from the irrotational free stream, for the case where this interface is subject to streamwise cyclic disturbances to its undisturbed shape. A linearized solution to this equation shows that a sinusoidal disturbance of wavelength \u03bb propagates as one mode of a neutrally stable Kelvin-Helmholtz wave with velocity \u03c9\u03bb[1 \u2212 exp (\u22124\u03c0\u03b4/\u03bb)]/4\u03c0 relative to the fluid at infinity. Numerical solutions of the full nonlinear equation for a range of wavelengths and finite disturbance amplitudes indicate different behaviour. For sufficiently large amplitude the interface valleys evolve into long re-entrant wedges of irrotational fluid which are 'entrained' into the layer and which are separated from the free stream by lobes or bulges of rotational fluid. This single-mode nonlinear interfacial distortion could be generated over a broad wavelength range with no indication of preferential scaling based on \u03b4. It is suggested that the interface behaviour bears distinct resemblance to flow features observed at the interface between turbulent and non-turbulent fluid in recent smoke-in-air flow-visualization studies of the outer part of a constant pressure turbulent boundary layer. The calculated rotational fluid lobe velocities, which are not very different from the equivalent linearized wave velocities, are found to be in reasonable agreement with the few existing measurements of the velocity of bulges at the turbulent\u2013nonturbulent fluid interface, while the computed velocity field in the lobe is in qualitative agreement with the general flow pattern observed in experiments. In the absence of a preferred scale or range of scales for the development of the interfacial distortion, however, it is concluded that the present results cannot be interpreted as supporting the hypothesis of the presence of large-scale coherent motions in the outer part of the layer.", "date": "1981-07", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "108", "publisher": "Cambridge University Press", "pagerange": "401-421", "id_number": "CaltechAUTHORS:20181120-153059939", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181120-153059939", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "doi": "10.1017/s0022112081002188", "resource_type": "article", "pub_year": "1981", "author_list": "Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/1terv-23z96", "eprint_id": 91096, "eprint_status": "archive", "datestamp": "2023-08-19 14:02:55", "lastmod": "2023-10-19 22:08:41", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Phillips-W-R-C", "name": { "family": "Phillips", "given": "W. R. C." } } ] }, "title": "On a generalization of Kaden's problem", "ispublished": "pub", "full_text_status": "restricted", "note": "\u00a9 1981 Cambridge University Press. \n\n(Received 3 January 1980 and in revised form 13 May 1980) \n\nThis research was partially supported by the National Energy Research, Development and Demonstration Council of Australia under contract no. 9240.", "abstract": "Kaden's problem of the roll-up of an initially planar semi-infinite vortex sheet with a parabolic distribution of circulation is extended to include vortex sheets exhibiting a general power law circulation distribution, resulting in the presence of a power law, and in one case a logarithmic-like, velocity-field singularity. Both semi-infinite and infinite initially plane sheets with this property are considered and the form of their roll-up in the similarity plane, into single and double-branched spirals respectively, is obtained numerically. Estimates of the Betz constant obtained from the solutions are found to be significantly different from values predicted by the Betz approximation.", "date": "1981-03", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "104", "publisher": "Cambridge University Press", "pagerange": "45-53", "id_number": "CaltechAUTHORS:20181120-153059853", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181120-153059853", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "National Energy Research, Development and Demonstration Council (Australia)", "grant_number": "9240" } ] }, "doi": "10.1017/s0022112081002802", "resource_type": "article", "pub_year": "1981", "author_list": "Pullin, D. I. and Phillips, W. R. C." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/nw5dq-jpx53", "eprint_id": 91072, "eprint_status": "archive", "datestamp": "2023-08-19 13:07:30", "lastmod": "2023-10-19 22:06:46", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Perry-A-E", "name": { "family": "Perry", "given": "A. E." } } ] }, "title": "Some flow visualization experiments on the starting vortex", "ispublished": "pub", "full_text_status": "public", "note": "\u00a9 1980 Cambridge University Press. \n\nReceived 4 December 1978. \n\nThe authors would like to thank Dr M. S. Chong who wrote the Fortran programmes for the PDP 11/10 and also Mr D. Gardner who very ably handled the photography. \n\nThis work was supported by the Australian Research Grants Committee.\n\nPublished - some_flow_visualization_experiments_on_the_starting_vortex.pdf
", "abstract": "A simple dye in water method has been used to visualize the growth of a two-dimensional starting flow vortex formed at a wedge-like sharp edge. Several cases were tested corresponding to different wedge angles and to different values of the time exponent in the velocity\u2013time power law describing the starting flow. Photographic sequences showing the time-wise primary vortex growth are presented from which various secondary-flow details are identified. For the larger wedge angles these include a strong secondary vortex and in some cases a small separation bubble-like flow region immediately adjacent to the wedge apex. For a thin-wedge model the formation of what might be interpreted as small rotation centres along the outer turns of the primary-vortex shear layer is observed but these are not seen as a manifestation of an instability phenomenon in the fluid. Measurements of the trajectories of the primary-vortex centre are compared with the predictions of an inviscid similarity theory of the vortex growth. Although the appropriate Reynolds number in the present experiments was relatively low, comparison between theory and experiments is regarded as reasonable with differences being attributed to viscous effects absent in the similarity theory, and also to apparatus wall effects.", "date": "1980-03-25", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "97", "number": "2", "publisher": "Cambridge University Press", "pagerange": "239-255", "id_number": "CaltechAUTHORS:20181120-130226804", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181120-130226804", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Australian Research Grants Committee" } ] }, "doi": "10.1017/S0022112080002546", "primary_object": { "basename": "some_flow_visualization_experiments_on_the_starting_vortex.pdf", "url": "https://authors.library.caltech.edu/records/nw5dq-jpx53/files/some_flow_visualization_experiments_on_the_starting_vortex.pdf" }, "resource_type": "article", "pub_year": "1980", "author_list": "Pullin, D. I. and Perry, A. E." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/1s8q3-1bh63", "eprint_id": 4159, "eprint_status": "archive", "datestamp": "2023-09-13 16:45:42", "lastmod": "2023-10-23 20:37:45", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Vortex ring formation at tube and orifice openings", "ispublished": "pub", "full_text_status": "public", "note": "Copyright \u00a9 1979 American Institute of Physics. \n\nReceived 12 June 1978.", "abstract": "The formation, at tube and orifice openings, of vortex rings generated by a piston moving with velocity proportional to time to some power m, is considered. The expansion of the axisymmetric generating flow about the circular forming edge is used in conjunction with the similarity theory of edge vortex growth to model the ring formation process. For large Reynolds numbers the ring diameter and circulation are not strongly dependent on the piston velocity profile. However, the ring viscous subcore shows peaks in the tangential velocity profile only if m < (\u03c0\u2013\u03b8)/(2\u03c0\u2013\u03b8), where \u03b8 is the edge forming angle.", "date": "1979-03-01", "date_type": "published", "publication": "Physics of Fluids", "volume": "22", "number": "3", "publisher": "Physics of Fluids", "pagerange": "401-403", "id_number": "CaltechAUTHORS:PULpof79", "issn": "1070-6631", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:PULpof79", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.862606", "primary_object": { "basename": "PULpof79.pdf", "url": "https://authors.library.caltech.edu/records/1s8q3-1bh63/files/PULpof79.pdf" }, "resource_type": "article", "pub_year": "1979", "author_list": "Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/w55wf-61862", "eprint_id": 91095, "eprint_status": "archive", "datestamp": "2023-08-19 11:41:18", "lastmod": "2023-10-19 22:08:37", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Large-scale structure of unsteady self-similar rolled-up vortex sheets", "ispublished": "pub", "full_text_status": "restricted", "note": "\u00a9 1978 Cambridge University Press. \n\n(Received 22 September 1977 and in revised form 17 February 1978) \n\nThe author wishes to thank Dr A. E. Perry for several valuable discussions.", "abstract": "Two problems involving the unsteady motion of two-dimensional vortex sheets are considered. The first is the roll-up of an initially plane semi-infinite vortex sheet while the second is the power-law starting flow past an infinite wedge with separation at the wedge apex modelled by a growing vortex sheet. In both cases well-known similarity solutions are used to transform the time-dependent problem for the sheet motion into an integro-differential equation. Finite-difference numerical solutions to these equations are obtained which give details of the large-scale structure of the rolled-up portion of the sheet. For the semi-infinite sheet good agreement with Kaden's asymptotic spiral solution is obtained. However, for the starting-flow problem distortions in the sheet shape and strength not predicted by the leading-order asymptotic solutions were found to be significant.", "date": "1978-10-13", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "88", "number": "3", "publisher": "Cambridge University Press", "pagerange": "401-430", "id_number": "CaltechAUTHORS:20181120-153059718", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181120-153059718", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "doi": "10.1017/s0022112078002189", "resource_type": "article", "pub_year": "1978", "author_list": "Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/wajbs-s5a30", "eprint_id": 3270, "eprint_status": "archive", "datestamp": "2023-08-22 01:40:31", "lastmod": "2023-10-16 15:46:11", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } } ] }, "title": "Kinetic models for polyatomic molecules with phenomenological energy exchange", "ispublished": "pub", "full_text_status": "public", "note": "Copyright \u00a9 1978 American Institute of Physics \n\nReceived 4 October 1976; final manuscript received 21 September 1977 \n\nThe help and encouragement of Dr. J. K. Harvey of the Department of Aeronautics, Imperial College, London, is gratefully acknowledged.", "abstract": "Models of the collision integral are developed for polyatomic structureless molecules subject to certain classes of phenomenological energy exchange between internal and translational energy modes in binary collisions. The exchange is described either by a model differential cross section for energy scattering or equivalently by a set of pair pseudo-internal coordinates which correlate pre- and post- collision values of the particle energies. Restrictions placed on admissible models of the exchange process are identified and one recently proposed special model is reformulated under these conditions. Chapman\u2013Enskog type transport properties for this model are evaluated and its behavior in the context of the Monte-Carlo direct simulation method is discussed briefly.", "date": "1978-02-01", "date_type": "published", "publication": "Physics of Fluids", "volume": "21", "number": "2", "publisher": "Physics of Fluids", "pagerange": "209-216", "id_number": "CaltechAUTHORS:PULpof78", "issn": "0031-9171", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:PULpof78", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "GALCIT" } ] }, "doi": "10.1063/1.862215", "primary_object": { "basename": "PULpof78.pdf", "url": "https://authors.library.caltech.edu/records/wajbs-s5a30/files/PULpof78.pdf" }, "resource_type": "article", "pub_year": "1978", "author_list": "Pullin, D. I." }, { "id": "https://authors.library.caltech.eduhttps://authors.library.caltech.edu/records/wdwep-nrk23", "eprint_id": 91105, "eprint_status": "archive", "datestamp": "2023-08-19 10:19:15", "lastmod": "2023-10-19 22:09:36", "type": "article", "metadata_visibility": "show", "creators": { "items": [ { "id": "Pullin-D-I", "name": { "family": "Pullin", "given": "D. I." } }, { "id": "Harvey-J-K", "name": { "family": "Harvey", "given": "J. K." } } ] }, "title": "A numerical simulation of the rarefied hypersonic flat-plate problem", "ispublished": "pub", "full_text_status": "restricted", "note": "\u00a9 1976 Cambridge University Press. \n\n(Received 3 February 1976) \n\nThe authors wish to thank Professor G. A. Bird, who kindly supplied his 'Universal' program, with which the energy-sink and restricted-exchange model calculations were performed. This program was also used to check other results presented herein obtained using the authors' own programs. The research was sponsored by the Science Research Council.", "abstract": "The direct-simulation Monte-Carlo method for the full Boltzmann equation is applied to the problem of rarefied hypersonic flow of rotationally excited N2 past the leading edge of a two-dimensional flat plate aligned with the free stream. An approximate collision model representing rotational\u2013translational energy exchanges is developed for use in the calculations. The effects of this and other inelastic collision models and of the single-parameter Maxwell gas\u2013surface interaction law on the flow in the kinetic/transition regime are discussed.", "date": "1976-12-22", "date_type": "published", "publication": "Journal of Fluid Mechanics", "volume": "78", "number": "4", "publisher": "Cambridge University Press", "pagerange": "689-707", "id_number": "CaltechAUTHORS:20181120-153100681", "issn": "0022-1120", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181120-153100681", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Science Research Council (SRC)" } ] }, "doi": "10.1017/s0022112076002693", "resource_type": "article", "pub_year": "1976", "author_list": "Pullin, D. I. and Harvey, J. K." } ]