[ { "id": "authors:x7ezb-a0s48", "collection": "authors", "collection_id": "x7ezb-a0s48", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140929-131815791", "type": "book_section", "title": "Evaluation of Hypervelocity Carbon Dioxide Blunt Body Experiments in an Expansion Tube Facility", "book_title": "49th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition", "author": [ { "family_name": "Sharma", "given_name": "M.", "clpid": "Sharma-M" }, { "family_name": "Swantek", "given_name": "A. B.", "clpid": "Swantek-A-B" }, { "family_name": "Flaherty", "given_name": "W.", "clpid": "Flaherty-W" }, { "family_name": "Austin", "given_name": "J. M.", "clpid": "Austin-J-M" }, { "family_name": "Doraiswamy", "given_name": "S.", "clpid": "Doraiswamy-S" }, { "family_name": "Candler", "given_name": "G. V.", "clpid": "Candler-G-V" } ], "abstract": "This work represents efforts to study high-enthalpy carbon dioxide flows in anticipation\nof the upcoming Mars Science Laboratory (MSL) and future missions. The\ncurrent study extends the previous presentation of experimental results by the comparison\nnow with axisymmetric simulations incorporating detailed thermochemical\nmodeling. The work is motivated by observed anomalies between experimental\nand numerical studies in hypervelocity impulse facilities. In this work, experiments\nare conducted in the Hypervelocity Expansion Tube (HET) which, by virtue of its\nflow acceleration process, exhibits minimal freestream dissociation in comparison\nto reflected shock tunnels. This simplifies the comparison with computational result\nas freestream dissociation and considerable thermochemical excitation can be\nneglected. Shock shapes of the Laboratory aeroshell and spherical geometries are\ncompared with numerical simulations. In an effort to address surface chemistry\nissues arising from high-enthalpy carbon dioxide ground-test based experiments,\nspherical stagnation point and aeroshell heat transfer distributions are also compared\nwith simulation. The shock stand-off distance has been identified in the\npast as sensitive to the thermochemical state and as such, is used here as an experimental\nmeasureable for comparison with CFD and two different theoretical\nmodels. For low-density, small-scale experiments it is seen that models based upon\nassumptions of large binary scaling values are unable to match the experimental\nand numerical results. Very good agreement between experiment and CFD is seen\nfor all shock shapes and heat transfer distributions fall within the non-catalytic and\nsuper-catalytic solutions.", "doi": "10.2514/6.2011-136", "isbn": "978-1-60086-950-1", "publisher": "AIAA", "place_of_publication": "Red Hook, NY", "publication_date": "2011-01" }, { "id": "authors:8nsr4-fx472", "collection": "authors", "collection_id": "8nsr4-fx472", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140930-075835687", "type": "book_section", "title": "Expansion Tube Investigation of Shock Stand-Off Distances in High-Enthalpy CO_2 Flow Over Blunt Bodies", "book_title": "48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace", "author": [ { "family_name": "Sharma", "given_name": "M.", "clpid": "Sharma-M" }, { "family_name": "Swantek", "given_name": "A. B.", "clpid": "Swantek-A-B" }, { "family_name": "Flaherty", "given_name": "W.", "clpid": "Flaherty-W" }, { "family_name": "Austin", "given_name": "J. M.", "clpid": "Austin-J-M" }, { "family_name": "Glumac", "given_name": "N. G.", "clpid": "Glumac-N-G" } ], "abstract": "The shock standoff distance in front of a blunt body is sensitive to the thermochemical\nstate of the free stream. Recently, experimental and numerical studies\nhave reported significantly different bow shock profiles in high-enthalpy carbon\ndioxide flows, a discrepancy that may result from non-equilibrium processes during\nflow acceleration in ground-based facilities. In this work, an expansion tube is used\nto create a Mach 5.7 carbon dioxide flow, matching the stagnation enthalpy and\nthe velocity of previous studies. Images of shock layers are obtained for spherical\ngeometries and a scaled model of the Mars Science Lander. Different sphere\ndiameters are used in order to access non-equilibrium and equilibrium stagnation\nline shock profiles predicted by theory. Mars Science Lander profiles at zero angle\nof attack are in good agreement with available data from the LENS X expansion\ntunnel facility, confirming results are facility-independent for the same type of flow\nacceleration, and indicating the flow velocity is a suitable first-order matching parameter\nfor comparative testing. Heat transfer measurements on the Mars Science\nLander are also presented for the three different angle of attacks, and the results\nare consistent with previous studies. Initial results from a proposed organo-metallic\nbased emission spectroscopy technique for bow shock layer interrogation are also\npresented.", "doi": "10.2514/6.2010-1566", "isbn": "978-1-60086-959-4", "publisher": "AIAA", "place_of_publication": "Reston, VA", "publication_date": "2010-01" }, { "id": "authors:q4jy0-7ag21", "collection": "authors", "collection_id": "q4jy0-7ag21", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140930-080858431", "type": "book_section", "title": "Spectroscopic Measurements in the Shock Relaxation Region of a Hypervelocity Mach Reflection", "book_title": "39th AIAA Fluid Dynamics Conference", "author": [ { "family_name": "Sharma", "given_name": "M.", "clpid": "Sharma-M" }, { "family_name": "Austin", "given_name": "J. M.", "clpid": "Austin-J-M" }, { "family_name": "Glumac", "given_name": "N. G.", "clpid": "Glumac-N-G" }, { "family_name": "Massa", "given_name": "L.", "clpid": "Massa-L" } ], "abstract": "We examine the spatial temperature profile in the non-equilibrium relaxation region\nbehind a stationary shock wave. The normal shock wave is established through a Mach\nreflection configuration from an opposing wedge arrangement for a hypervelocity air Mach\n7.42 freestream. Schlieren images confirm that the shock configuration is steady and the\nlocation is repeatable. Emission spectroscopy is used to identify dissociated species and to\nobtain vibrational temperature measurements using the NO and OH A-X band sequences.\nTemperature measurements are presented at selected locations behind the normal shock.\nLIFBASE is used as the simulation spectrum software for OH temperature-fitting, however the need to access higher vibrational and rotational levels for NO leads to the use of\nan in-house developed algorithm. For NO, results demonstrate the contribution of higher\nvibrational and rotational levels to the spectra at the conditions of this study. Very good\nagreement is achieved between the experimentally measured NO vibrational temperatures\nand calculations performed using a state-resolved, one-dimensional forced harmonic oscillator thermochemical model.", "doi": "10.2514/6.2009-4218", "isbn": "978-1-60086-971-6", "publisher": "AIAA", "place_of_publication": "Reston, VA", "publication_date": "2009-06" }, { "id": "authors:ejmnq-f2147", "collection": "authors", "collection_id": "ejmnq-f2147", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140930-150440935", "type": "book_section", "title": "Triple point shear layers in hypervelocity flow", "book_title": "26th International Symposium on Shock Waves", "author": [ { "family_name": "Sharma", "given_name": "M.", "clpid": "Sharma-M" }, { "family_name": "Massa", "given_name": "L.", "clpid": "Massa-L" }, { "family_name": "Austin", "given_name": "J. M.", "clpid": "Austin-J-M" } ], "contributor": [ { "family_name": "Hannemann", "given_name": "Klaus", "clpid": "Hannemann-K" }, { "family_name": "Seiler", "given_name": "Friedrich", "clpid": "Seiler-F" } ], "abstract": "Thermochemical processes such as dissociation and vibrational excitation can have a substantial impact on the gas dynamics of planetary entry. A critical question that confronts vehicle designers is the role of such molecular effects on transition and turbulence. In high stagnation enthalpy flows, thermochemical processes have been observed to affect transition to turbulence in boundary layers through modifications to the mean flow profile as well as to flow stability [1-3].", "doi": "10.1007/978-3-540-85168-4_117", "isbn": "978-3-540-85167-7", "publisher": "Springer", "place_of_publication": "Berlin", "publication_date": "2009", "pages": "725-730" }, { "id": "authors:fhhy2-j4421", "collection": "authors", "collection_id": "fhhy2-j4421", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141006-083036975", "type": "book_section", "title": "Influence of thermochemistry on Mach reflection in\n hypersonic flow", "book_title": "44th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit", "author": [ { "family_name": "Sharma", "given_name": "M.", "clpid": "Sharma-M" }, { "family_name": "Austin", "given_name": "J. M.", "clpid": "Austin-J-M" }, { "family_name": "Glumac", "given_name": "N. G.", "clpid": "Glumac-N-G" } ], "abstract": "Real gas thermochemistry can significantly impact the aerodynamics of hypersonic systems. For example, shock stand-off distance in front of a blunt body has been shown to depend on the degree of chemical\ndissociation. High temperature effects can also alter shock-shock interaction phenomena, but the degree of\nthe modification and its consequences can be challenging to predict. Sanderson et al. experimentally investigated oblique shock impingment on a bow shock (Edney type IV configuration) in a flow with significant\ngas dissociation. Previous studies had suggested significant increase in heat transfer at jet impingement\ndue to real gas effects, however, experiments showed no dependence of peak heat transfer rate on stagnation\nenthalpy. The influence of nonequilibrium gas chemistry on Mach and regular shock reflection has been investigated in a number of numerical studies. Burtschell et al. numerically investigated a wedge geometry\nlocated in a Mach 7 free stream, a setup similar to that used in the present experimental work. Mach stem\nheight and hysteresis behavior was examined. Burtschell et al. found a strong dependence of transition\nangles, Mach stem height and location on the gas flow model. For a given wedge angle, the inclusion of\nreal gas chemistry led to a significant decrease in Mach stem height. Chemical-vibration coupling, however,\nslightly increased the height of the Mach stem. Direct Monte-Carlo simulations of a shock reflection with\nand without real gas effects carried out by Gimelschein et al. also found a substantial effect on Mach stem\nheight and transition angle. However, an experimental study in dissociating nitrogen and carbon dioxide,\nionizing argon and frozen argon could detect no effect on the transition condition due to finite relaxation\nlength at the conditions of the experiment.\n\nIn the present work, we experimentally investigate a Mach reflection generated by two opposing wedges\nin a Mach 7.1 free stream. The main goal of this work is to determine directly what kinds of real gas effects\noccur behind a normal shock in a Mach reflection configuration for a previously selected run condition.\nExperiments are carried out in an expansion tube facility which is capable of simulating high enthalpy\nhypersonic flight conditions, and a significant degree of vibrational excitation and chemical dissociation are\nexpected behind the normal shock.\n\nIn high enthalpy gas flows, emission spectroscopy can be used to characterize the test gas composition\nand thermodynamic state. As impulse facilities, expansion tubes produce a challenging experimental environment for probe measurements with issues such as short test times, high temperatures and velocities, and\ndiaphragm fragmentation. The non-intrusive nature of spectroscopy makes it an attractive technique\nfor determining flow field properties in impulse facilities. Spectrally resolved studies have been previously\nused as a means towards characterizing high-enthalpy run conditions. Work completed at the X1 and X2\nsuperorbital expansion tube facilities used emission spectroscopy to measure electron number density behind\na bow shock and to identify sources of visible radiation. Time-resolved spectral methods were used in\nthe JX1 expansion tube facility to determine the useful test time. Using the CARS technique, temperature\nprofiles were determined for a hypervelocity blunt body flow field using the T3 shock tunnel facility. Using\nthe free piston shock tube/tunnel facility TCM2, laser spectroscopy was used for species identification and\nshock front temperature profile diagnostics and spontaneous Raman spectroscopy was used to analyze the\nself-luminosity of nitrogen hypersonic flows for varying enthalpy conditions.\n\nIn the current experiments, asymmetric wedges are used to generate a Mach stem, with a free shear layer\nat each triple point. Imaged spectroscopic measurements behind the Mach stem are presented. The spectra\nconfirms flow dissociation and verifies the appropriateness of a run condition which in the future is to be\nused towards investigating high-temperature effects upon shear layer structure in hypersonic flow.", "doi": "10.2514/6.2008-5066", "isbn": "978-1-60086-992-1", "publisher": "AIAA", "place_of_publication": "Reston, VA", "publication_date": "2008-07" }, { "id": "authors:2q2r7-k2q35", "collection": "authors", "collection_id": "2q2r7-k2q35", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140930-144402979", "type": "book_section", "title": "Diagnostic Modelling of an Expansion Tube Operating Condition for a Hypersonic Free Shear Layer Experiment", "book_title": "Proceedings of the Sixteenth Australasian Fluid Mechanics Conference", "author": [ { "family_name": "McGilvray", "given_name": "M.", "clpid": "McGilvray-M" }, { "family_name": "Austin", "given_name": "J. M.", "clpid": "Austin-J-M" }, { "family_name": "Sharma", "given_name": "M.", "clpid": "Sharma-M" }, { "family_name": "Jacobs", "given_name": "P. A.", "clpid": "Jacobs-P-A" }, { "family_name": "Morgan", "given_name": "R. G.", "clpid": "Morgan-R-G" } ], "abstract": "Computational simulations of the AIR-1 test condition in the\nUniversity of Illinois' Hypervelocity Expansion Tube were conducted\nto verify facility operation and to obtain free stream\nproperties that are otherwise difficult to measure. Two types\nof simulation were undertaken. The first was a one-dimensional\nsimulation of the entire facility and the second was a hybrid simulation,\ncombining a one-dimensional simulation of the shock\ntube section with a two-dimensional simulation of the acceleration\ntube. The one-dimensional simulation matched the experimental\ndata well, however the two-dimensional simulation\ndid not initially match the experimental measurements of shock\nspeed and test gas pitot pressure. Further investigation showed\nthe shock speed discrepancy was consistent with air contamination\ninto the acceleration tube and subsequent two-dimensional\nsimulations assuming 10% air contamination showed reasonable\nagreement with experimental data.\n\nUsing data taken from the two-dimensional simulation of the\nexpansion tube as a transient inflow condition, modelling was\nundertaken of a free shear layer experiment being conducted in\nthe facility. Results from equilibrium, finite rate, and perfect\ngas models were compared. The finite rate simulation provides\nthe best agreement with experimental Schlieren images, with\nthe simulation capturing the major flow structures seen in experiments.", "isbn": "9781864998948", "publisher": "University of Queensland", "place_of_publication": "St Lucia, Queensland, Australia", "publication_date": "2007-12", "pages": "385-393" }, { "id": "authors:7pqc3-73s36", "collection": "authors", "collection_id": "7pqc3-73s36", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140930-100227099", "type": "book_section", "title": "Design and Characterization of a Hypervelocity Expansion Tube Facility", "book_title": "45th AIAA Aerospace Sciences Meeting and Exhibit", "author": [ { "family_name": "Dufrene", "given_name": "A.", "clpid": "Dufrene-A" }, { "family_name": "Sharma", "given_name": "M.", "clpid": "Sharma-M" }, { "family_name": "Austin", "given_name": "J. M.", "clpid": "Austin-J-M" } ], "abstract": "We report on the design and characterization of a 152 mm diameter expansion tube capable of accessing a range of high enthalpy test conditions\nwith Mach numbers up to 7.1 for aerodynamic studies. Expansion tubes\nhave the potential to offer a wide range of test flow conditions as gas acceleration is achieved through interaction with an unsteady expansion wave\nrather than expansion through a fixed area ratio nozzle. However, the range\nof test flow conditions is in practice limited by a number of considerations\nsuch as short test time and large amplitude flow disturbances. We present\na generalized design strategy for small-scale expansion tubes. As a starting\npoint, ideal gas dynamic calculations for optimal facility design to maximize\ntest time at a given Mach number test condition are presented, together\nwith a correction for the expansion head reflection through a non-simple\nregion. A compilation of practical limitations that have been identified for\nexpansion tube facilities such as diaphragm rupture and flow disturbance\nminimization is then used to map out a functional design parameter space.\nExperimentally, a range of test conditions have been verified through pitot\npressure measurements and analysis of schlieren images of flow over simple\ngeometries. To date there has been good agreement between theoretical\nand experimental results.", "doi": "10.2514/6.2007-1327", "isbn": "978-1-62410-012-3", "publisher": "AIAA", "place_of_publication": "Reston, VA", "publication_date": "2007-01" } ]