[
{
"id": "https://authors.library.caltech.edu/records/g851r-ap902",
"eprint_status": "archive",
"datestamp": "2024-01-22 19:36:37",
"lastmod": "2024-01-23 00:21:31",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Gramiscelli-Hasparyk-Barbara",
"name": {
"family": "Gramiscelli Hasparyk",
"given": "Barbara"
}
},
{
"id": "Jordan-Peter",
"name": {
"family": "Jordan",
"given": "Peter"
},
"orcid": "0000-0001-8576-5587"
},
{
"id": "Lebedev-Anton",
"name": {
"family": "Lebedev",
"given": "Anton"
}
},
{
"id": "Lesshafft-Lutz",
"name": {
"family": "Lesshafft",
"given": "Lutz"
},
"orcid": "0000-0002-2513-4553"
},
{
"id": "Pickering-Ethan-M",
"name": {
"family": "Pickering",
"given": "Ethan M."
},
"orcid": "0000-0002-4485-6359"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Two-point measurements on the acoustic field of subsonic turbulent jets",
"ispublished": "unpub",
"full_text_status": "public",
"note": "
© 2023 by Barbara G. Hasparyk; Peter Jordan; Anton Lebedev; Lutz Lesshafft; Ethan Pickering; Tim Colonius. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission.
",
"abstract": "\n
\n
Two-point acoustic measurements are made for subsonic, isothermal turbulent jets over a range of Mach numbers, spanning from 0.4 to 0.9. The measurements are made using two antennae, each with 18 azimuthally distributed microphones, that can be independently displaced in the streamwise direction. The measurement system is used to construct CSD matrices of the sound field for each Mach number. We report a detailed analysis of the two-point structure of the sound field, which is decomposed using a Fourier series in azimuth, Fourier transform in time, and Spectral Proper Orthogonal Decomposition in the inhomogeneous streamwise direction. Analysed in this way, Mach- and Strouhal-number dependencies of the low-rank structure of the sound field are explored. Based on Crow’s model [1], we use a wavepacket source to explore features of the axisymmetric mode of the radiated sound. The model considers all components of Lighthill’s stress tensor to understand the physics behind the observed trends, and this suggests a modification to Crow’s wavepacket. The model proposed reproduces qualitatively some of the different scalings observed at low and high polar angles.
\n
\n
",
"date": "2023-06-08",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"place_of_pub": "Reston, VA",
"pagerange": "2023-4290",
"isbn": "978-1-62410-704-7",
"book_title": "AIAA AVIATION 2023 Forum",
"official_url": "https://authors.library.caltech.edu/records/g851r-ap902",
"other_numbering_system": {
"items": [
{
"id": "2023-4290",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2023-4290",
"resource_type": "conference_item",
"pub_year": "2023",
"author_list": "Gramiscelli Hasparyk, Barbara; Jordan, Peter; et el."
},
{
"id": "https://authors.library.caltech.edu/records/2xr33-eqr78",
"eprint_status": "archive",
"datestamp": "2024-01-22 23:54:33",
"lastmod": "2024-01-23 00:15:21",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Nekkanti-Akhil",
"name": {
"family": "Nekkanti",
"given": "Akhil"
},
"orcid": "0000-0002-2173-8704"
},
{
"id": "Schmidt-Oliver-T",
"name": {
"family": "Schmidt",
"given": "Oliver T."
},
"orcid": "0000-0002-7097-0235"
},
{
"id": "Albuquerque-Maia-Igor",
"name": {
"family": "Maia",
"given": "Igor"
},
"orcid": "0000-0003-2530-0897"
},
{
"id": "Jordan-Peter",
"name": {
"family": "Jordan",
"given": "Peter"
},
"orcid": "0000-0001-8576-5587"
},
{
"id": "Heidt-Liam",
"name": {
"family": "Heidt",
"given": "Liam"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Bispectral mode decomposition of axisymmetrically and non-axisymmetrically forced turbulent jets",
"ispublished": "unpub",
"full_text_status": "public",
"note": "© 2023 by the American Institute of Aeronautics and Astronautics, Inc.
",
"abstract": "Large-eddy simulations (LES) of a turbulent unforced jet at Re = 50,000 and M\u2c7c= 0.4, and jets forced at azimuthal wavenumbers m = 0, m = 1, m = 2 and m = 6 are performed. The objective of this study is to characterize the nonlinear interactions that are initiated by the forcing. To achieve this, we used the bispectral mode decomposition (BMD) technique, which is tailored to extract flow structures associated with triadic interactions. Azimuthal wavenumber triads are investigated using the cross-spectral variant of BMD. Axisymmetric forcing generates peaks at the forcing frequency and its harmonics in the m = 0 component only, whereas non-axisymmetric forcing generates peaks at different azimuthal wavenumbers. The latter aspect is investigated using cross-BMD. Forcing the jet at m = 1, the only odd-m forcing case considered, creates a cascade of triads that generates peaks at the forcing frequency and its odd harmonics at odd azimuthal wavenumbers and even harmonics at even azimuthal wavenumbers. Forcing the jet at m = m_f azimuthal wavenumbers produces peaks at the odd harmonics in the odd integer multiples of m_f and at even harmonic frequencies in the even integer multiples of m_f.
",
"date": "2023-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"place_of_pub": "Reston, VA",
"pagerange": "2023-3651",
"isbn": "978-1-62410-704-7",
"book_title": "AIAA AVIATION 2023 Forum",
"official_url": "https://authors.library.caltech.edu/records/2xr33-eqr78",
"other_numbering_system": {
"items": [
{
"id": "2023-3651",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2023-3651",
"resource_type": "conference_item",
"pub_year": "2023",
"author_list": "Nekkanti, Akhil; Schmidt, Oliver T.; et el."
},
{
"id": "https://authors.library.caltech.edu/records/q0aaz-jzg60",
"eprint_status": "archive",
"datestamp": "2024-01-22 18:27:36",
"lastmod": "2024-01-22 18:27:36",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Heidt-Liam",
"name": {
"family": "Heidt",
"given": "Liam"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Nekkanti-Akhil",
"name": {
"family": "Nekkanti",
"given": "Akhil"
},
"orcid": "0000-0002-2173-8704"
},
{
"id": "Schmidt-Oliver-T",
"name": {
"family": "Schmidt",
"given": "Oliver T."
},
"orcid": "0000-0002-7097-0235"
},
{
"name": {
"family": "Maia",
"given": "Igor"
}
},
{
"id": "Jordan-Peter",
"name": {
"family": "Jordan",
"given": "Peter"
},
"orcid": "0000-0001-8576-5587"
}
]
},
"title": "Cyclostationary analysis of forced turbulent jets",
"ispublished": "unpub",
"full_text_status": "public",
"note": "\n
© 2023 by Liam Heidt, Tim Colonius, Akhil Nekkanti, Oliver T. Schmidt, Igor A. Maia, Peter Jordan. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission.
\n
",
"abstract": "\n
\n
A variety of actuation methods have been applied to turbulent jets with the aim of reducing far-field sound. However, a detailed understanding of the mechanisms by which actuation alters the turbulence and far-field sound is lacking. We investigate the effect of periodic acoustic forcing by performing a series of large-eddy simulations of turbulent axisymmetric subsonic and supersonic jets subjected to periodic forcing at several frequencies and amplitudes. To analyze data from the forced jets, we employ cyclostationary analysis, which is an extension of the statistically stationary framework to processes that have periodically varying statistics. Both low- St_f=0.3 and high-frequency St_f=1.5 forcing generate an energetic tonal response but have limited effect on the time-averaged mean with a forcing amplitude greater than 1% required to achieve a small change. Similar trends were seen for the turbulent kinetic energy and the energy transfer between the mean and turbulent components. By applying cyclostationary spectral proper orthogonal decomposition (CS-SPOD), we investigate how the dominant coherent structures are modified and modulated by the forcing. For St_f=0.3, a broadband increase in the energy of the dominant coherent structures was found. The low-frequency coherent structures were found to be strongly phase dependent, with substantial energy coupled to the high-velocity and high-shear regions of the mean flow. In contrast, forcing at St_f=1.5 resulted in a broadband decrease in the energy of the dominant coherent structures. No phase-dependent modulation of the low-frequency coherent structures was seen due to a large difference in the wavelength and spatial support between the coherent structures and the mean field. A reduced impact of the St_f=0.3 forcing on the supersonic jet is seen, while the St_f=1.5 forcing results in a similar impact.
\n
\n
\n
\n
",
"date": "2023-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"place_of_pub": "Reston, VA",
"pagerange": "2023-3652",
"isbn": "978-1-62410-704-7",
"book_title": "AIAA AVIATION 2023 Forum",
"official_url": "https://authors.library.caltech.edu/records/q0aaz-jzg60",
"other_numbering_system": {
"items": [
{
"id": "2023-3652",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2023-3652",
"resource_type": "conference_item",
"pub_year": "2023",
"author_list": "Heidt, Liam; Colonius, Tim; et el."
},
{
"id": "https://authors.library.caltech.edu/records/rdt9a-tra90",
"eprint_status": "archive",
"datestamp": "2024-01-22 23:31:34",
"lastmod": "2024-01-22 23:49:05",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Sleeman-Michael-K",
"name": {
"family": "Sleeman",
"given": "Michael K."
},
"orcid": "0000-0001-5949-9289"
},
{
"id": "Lakebrink-Matthew-T",
"name": {
"family": "Lakebrink",
"given": "Matthew T."
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Nonlinear stability of wall-bounded flows using the One-Way Navier-Stokes (OWNS) Equations",
"ispublished": "unpub",
"full_text_status": "public",
"note": "© 2023 by Michael K. Sleeman, Matthew T. Lakebrink, Tim Colonius. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission.
",
"abstract": "\n
\n
We extend the One-Way Navier Stokes (OWNS) approach to support nonlinear interactions between waves of different frequencies, which will enable nonlinear analysis of instability and transition. In linear OWNS, the linearized Navier-Stokes equations are modified such that upstream propagating modes are removed, so that they can be solved efficiently in the frequency domain as a spatial initial-value (marching) problem. Linear OWNS confers numerous advantages over the parabolized stability equations (PSE) that we seek to extend to nonlinear analysis. In the proposed method, the fully nonlinear Navier-Stokes equations are marched in the downstream direction. At each step of the march, the projection operator from the linear OWNS procedure is applied to (approximately) remove modes with upstream group velocity. We validate the method by examining the nonlinear evolution of two- and three-dimensional disturbances in a low-speed Blasius boundary layer by comparing with PSE and DNS results from the literature.
\n
\n
",
"date": "2023-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"place_of_pub": "Reston, VA",
"pagerange": "2023-3273",
"isbn": "978-1-62410-704-7",
"book_title": "AIAA AVIATION 2023 Forum",
"official_url": "https://authors.library.caltech.edu/records/rdt9a-tra90",
"other_numbering_system": {
"items": [
{
"id": "2023\u20133273",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2023-3273",
"resource_type": "conference_item",
"pub_year": "2023",
"author_list": "Sleeman, Michael K.; Lakebrink, Matthew T.; et el."
},
{
"id": "https://authors.library.caltech.edu/records/pb1ax-1p987",
"eprint_status": "archive",
"datestamp": "2024-01-23 00:18:07",
"lastmod": "2024-01-23 00:18:07",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Hou-Wei",
"name": {
"family": "Hou",
"given": "Wei"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Three-dimensional Stability and Resolvent Analysis of External Flows Over Spanwise-homogeneous Immersed Bodies",
"ispublished": "unpub",
"full_text_status": "public",
"note": "© 2023 by Wei Hou, Tim Colonius. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission.
",
"abstract": "\n
\n
We introduce a computationally efficient method to conduct three-dimensional stability and resolvent analyses of flow around nominally two-dimensional (spanwise homogeneous) bodies of arbitrary cross-sections. For incompressible flows, our method utilizes the immersed boundary (IB) method with a fast Lattice Green's Function (FLGF) solver for the associated Poisson-like equation and includes adaptive mesh refinement (AMR). We validate our algorithm by performing stability analyses of flow past a rotating cylinder and comparing our results with ones from the literature. We also demonstrate the capability of this algorithm by conducting a 2D resolvent analysis by considering the flow past a cylinder at Re = 100. Finally, we demonstrate the capability of this method to handle a wide range of length scales by conducting stability analysis of the flow past a cylinder at Re = 63 with a small control cylinder in its wake.
\n
\n
",
"date": "2023-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"place_of_pub": "Reston, VA",
"pagerange": "2023-3414",
"isbn": "978-1-62410-704-7",
"book_title": "AIAA AVIATION 2023 Forum",
"official_url": "https://authors.library.caltech.edu/records/pb1ax-1p987",
"other_numbering_system": {
"items": [
{
"id": "2023-3414",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2023-3414",
"resource_type": "conference_item",
"pub_year": "2023",
"author_list": "Hou, Wei and Colonius, Tim"
},
{
"id": "https://authors.library.caltech.edu/records/32wtz-93209",
"eprint_status": "archive",
"datestamp": "2024-01-25 22:46:27",
"lastmod": "2024-01-25 22:46:27",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Nekkanti-Akhil",
"name": {
"family": "Nekkanti",
"given": "Akhil"
},
"orcid": "0000-0002-2173-8704"
},
{
"id": "Schmidt-Oliver-T",
"name": {
"family": "Schmidt",
"given": "Oliver T."
},
"orcid": "0000-0002-7097-0235"
},
{
"name": {
"family": "Maia",
"given": "Igor"
}
},
{
"id": "Jordan-Peter",
"name": {
"family": "Jordan",
"given": "Peter"
},
"orcid": "0000-0001-8576-5587"
},
{
"id": "Heidt-Liam",
"name": {
"family": "Heidt",
"given": "Liam"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Triadic nonlinear interactions and acounstics of forced versus unforced turbulent jets",
"ispublished": "unpub",
"full_text_status": "public",
"note": "AN and OTS gratefully acknowledge support from Office of Naval Research grant N00014-20-1-2311 and National Science Foundation grant CBET 2046311.
",
"abstract": "We explore the potential of bispectral mode decomposition (BMD) for physical discovery in jet flows. BMD is a modal decomposition that is tailored to the extraction of flow structures involved in triadic interactions. Large-eddy simulations (LES) of turbulent forced and unforced round jets at Re = 50,000 and Mj = 0.4 are conducted and validated with the companion experiment at the Institut Pprime. The comparative BMD analysis reveals that triadic interactions in both forced and unforced jets are most prevalent in a welldefined region near and downstream of the closure of the potential core. A BMD analysis of far-field pressure sheds light on the previously reported observation that differenceinteractions are more efficient radiators of jet noise than the sum-interactions.
",
"date": "2022-07",
"date_type": "published",
"publisher": "Darmstadt University of Technology",
"pagerange": "149",
"book_title": "Proceedings of TSFP-12 (2022) Osaka",
"official_url": "https://authors.library.caltech.edu/records/32wtz-93209",
"funders": {
"items": [
{
"grant_number": "N00014-20-1-2311"
},
{
"grant_number": "CBET-2046311"
}
]
},
"primary_object": {
"basename": "149.pdf",
"url": "https://authors.library.caltech.edu/records/32wtz-93209/files/149.pdf"
},
"resource_type": "conference_item",
"pub_year": "2022",
"author_list": "Nekkanti, Akhil; Schmidt, Oliver T.; et el."
},
{
"id": "https://authors.library.caltech.edu/records/fv3se-97c55",
"eprint_id": 115434,
"eprint_status": "archive",
"datestamp": "2023-08-20 08:04:55",
"lastmod": "2024-01-25 16:36:53",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Kamal-Omar",
"name": {
"family": "Kamal",
"given": "Omar"
}
},
{
"id": "Rigas-Georgios",
"name": {
"family": "Rigas",
"given": "Georgios"
},
"orcid": "0000-0001-6692-6437"
},
{
"id": "Lakebrink-Matthew-T",
"name": {
"family": "Lakebrink",
"given": "Matthew T."
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Input/output analysis of a Mach-6 cooled-wall hypersonic boundary layer using the One-Way Navier-Stokes (OWNS) Equations",
"ispublished": "unpub",
"full_text_status": "public",
"note": "\u00a9 2022 by Omar Kamal, Georgios Rigas, Matthew T. Lakebrink, Tim Colonius. \n\nPublished Online: 20 Jun 2022.",
"abstract": "The dominant instability observed in adiabatic-wall flat-plate hypersonic boundary layers is the second Mack mode, which manifests itself as trapped acoustic waves between the wall and the relative sonic line. If the wall is highly cooled, not only is this mode destabilized, but an additional mode may emerge \u2013 the supersonic mode, which is characterized by an acoustic emission from the boundary layer. To investigate the input/output behavior of these boundary layers, we use the One-Way Navier-Stokes (OWNS) Equations, which efficiently approximate a rigorous parabolization of the equations by filtering out disturbances with upstream group velocity, resulting in memory and CPU savings compared to global methods on large grids. We investigate the mechanistic shift of the second mode in a 2D Mach-6 flat-plate boundary layer by examining how the optimal response varies with frequency and the wall temperature. Specifically, we tackle the global forced receptivity problem with highly-cooled-wall conditions by parametrically analyzing the optimal forcings and corresponding responses. We demonstrate that the optimal response shifts from the first to the second mode with increasing frequency, along with the excitation of the supersonic mode when the wall is sufficiently cooled. Although the aforementioned conclusions can also be ascertained from locally-parallel, linear stability theory (LST), we demonstrate that inter-modal interactions involving the supersonic mode locally affect the mode shapes that LST fails to capture. Furthermore, spatially transient or non-modal responses are observed in cases where LST predicts all modes to be stable.",
"date": "2022-06-27",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"place_of_pub": "Reston, VA",
"pagerange": "2022-3556",
"id_number": "CaltechAUTHORS:20220708-621988300",
"isbn": "978-1-62410-635-4",
"book_title": "AIAA AVIATION 2022 Forum",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220708-621988300",
"other_numbering_system": {
"items": [
{
"id": "2022-3556",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2022-3556",
"resource_type": "conference_item",
"pub_year": "2022",
"author_list": "Kamal, Omar; Rigas, Georgios; et el."
},
{
"id": "https://authors.library.caltech.edu/records/fbv3g-4t242",
"eprint_id": 115157,
"eprint_status": "archive",
"datestamp": "2023-08-20 07:57:36",
"lastmod": "2024-01-25 18:31:44",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Ozawa-Yuta",
"name": {
"family": "Ozawa",
"given": "Yuta"
}
},
{
"id": "Nishikori-Hiroki",
"name": {
"family": "Nishikori",
"given": "Hiroki"
}
},
{
"id": "Nagata-Takayuki",
"name": {
"family": "Nagata",
"given": "Takayuki"
}
},
{
"id": "Nonomura-Taku",
"name": {
"family": "Nonomura",
"given": "Taku"
}
},
{
"id": "Asai-Keisuke",
"name": {
"family": "Asai",
"given": "Keisuke"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "DMD-based Superresolution Measurement of a Supersonic Jet using Dual Planar PIV and Acoustic Data",
"ispublished": "unpub",
"full_text_status": "public",
"note": "© 2022 by Yuta Ozawa/Tohoku University. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission.
",
"abstract": "The present study proposes a framework of the superresolution measurement based on the dynamic mode decomposition (DMD) with the Kalman filter and Rauch–Tung–Striebel smoother. The dual-planar particle image velocimetry (PIV) systems were constructed to acquire the paired velocity fields of a Mach 1.1 supersonic jet. The acoustic measurement was simultaneously performed, and the velocity and acoustic data are used for the superresolution. Although the dual PIV system measures the basic characteristics of the velocity fields, all the DMD modes calculated by the exact DMD are decay modes due to the measurement noise. The superresolved velocity field shows smooth convection of the large-scale structures at the downstream side. Therefore, the proposed method is effective to reconstruct the entire flow fluctuation because the DMD modes express the linear dynamical system of the velocity fields.
",
"date": "2022-06-14",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"place_of_pub": "Reston, VA",
"pagerange": "2022-3065",
"id_number": "CaltechAUTHORS:20220614-222392000",
"isbn": "978-1-62410-664-4",
"book_title": "28th AIAA/CEAS Aeroacoustics 2022 Conference",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220614-222392000",
"other_numbering_system": {
"items": [
{
"id": "2022-3065",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2022-3065",
"resource_type": "conference_item",
"pub_year": "2022",
"author_list": "Ozawa, Yuta; Nishikori, Hiroki; et el."
},
{
"id": "https://authors.library.caltech.edu/records/e8rn0-34s44",
"eprint_id": 115433,
"eprint_status": "archive",
"datestamp": "2023-08-22 16:23:12",
"lastmod": "2024-01-25 18:58:53",
"type": "conference_item",
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"creators": {
"items": [
{
"id": "Araya-Daniel-B",
"name": {
"family": "Araya",
"given": "Daniel"
}
},
{
"id": "Araya-Neal",
"name": {
"family": "Bitter",
"given": "Neal"
}
},
{
"id": "Wheaton-Bradley-M",
"name": {
"family": "Wheaton",
"given": "Bradley M."
},
"orcid": "0009-0005-5765-0316"
},
{
"id": "Kamal-Omar",
"name": {
"family": "Kamal",
"given": "Omar"
},
"orcid": "0000-0002-3431-2964"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Knutson-Anthony",
"name": {
"family": "Knutson",
"given": "Anthony"
}
},
{
"id": "Johnson-Heath",
"name": {
"family": "Johnson",
"given": "Heath"
}
},
{
"id": "Nichols-Joseph",
"name": {
"family": "Nichols",
"given": "Joseph"
}
},
{
"id": "Candler-Graham-V",
"name": {
"family": "Candler",
"given": "Graham V."
}
},
{
"id": "Russo-Vincenzo",
"name": {
"family": "Russo",
"given": "Vincenzo"
}
},
{
"id": "Brehm-Christoph",
"name": {
"family": "Brehm",
"given": "Christoph"
},
"orcid": "0000-0002-9006-3587"
}
]
},
"title": "Assessment of Linear Methods for Analysis of Boundary Layer Instabilities on a Finned Cone at Mach 6",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Boundary Layer Transition; Parabolized Stability Equations; Direct Numerical Simulation; Adaptive Mesh Refinement; Vortex Structure; Compressible Flow; Air Forces; Boeing; Shape Functions; Singular Value Decomposition",
"abstract": "Boundary-layer instabilities of a finned cone at Mach = 6, Re = 8.4 x 10\u2076 /m, and zero incidence angle are examined using linear stability methods of varying fidelity and maturity. The geometry and laminar flow conditions correspond to experiments conducted at the Boeing Air Force Mach 6 Quiet Tunnel (BAM6QT) at Purdue University. Where possible, a common mean flow is utilized among the stability computations, and comparisons are made along the acreage of the cone where transition is first observed in the experiment. Stability results utilizing Linear Stability Theory (LST), planar Parabolized Stability Equations (planar-PSE), One-Way Navier Stokes (OWNS), forced direct numerical simulation (DNS), and Adaptive Mesh Refinement Wavepacket Tracking (AMR-WPT) are presented. One of the major findings of the work includes identification of a dominant three-dimensional vortex instability occurring at approximately 250 kHz that correlates well with experimental measurements of transition onset. With the exception of LST, all of the higher-fidelity linear methods considered in this work were consistent in predicting the initial growth and general structure of the vortex instability as it evolved downstream. OWNS analysis utilizing randomized wavenumber forcing identified possible nonmodal interactions contributing to the development of this vortex instability. Both forced DNS and AMR-WPT analysis demonstrated the utility of these methods in tracking either linear or nonlinear growth of disturbances. Finally, a new implementation of Input/Output (I/O) analysis is discussed and some of the challenges, opportunities, and development needs for all of the stability methods are presented.
",
"date": "2022-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"place_of_pub": "Reston, VA",
"pagerange": "2022-3247",
"id_number": "CaltechAUTHORS:20220708-930729800",
"isbn": "978-1-62410-635-4",
"book_title": "AIAA AVIATION 2022 Forum",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220708-930729800",
"other_numbering_system": {
"items": [
{
"id": "2022-3247",
"name": "AIAA Paper"
}
]
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"doi": "10.2514/6.2022-3247",
"resource_type": "conference_item",
"pub_year": "2022",
"author_list": "Araya, Daniel; Bitter, Neal; et el."
},
{
"id": "https://authors.library.caltech.edu/records/73t32-zaw93",
"eprint_status": "archive",
"datestamp": "2024-01-22 19:11:02",
"lastmod": "2024-01-22 19:11:02",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Lee-Chungil",
"name": {
"family": "Lee",
"given": "Chungil"
},
"orcid": "0000-0002-3629-427X"
},
{
"id": "Nishikori-Hiroki",
"name": {
"family": "Nishikori",
"given": "Hiroki"
}
},
{
"id": "Nagata-Takayuki",
"name": {
"family": "Nagata",
"given": "Takayuki"
},
"orcid": "0000-0003-3644-4888"
},
{
"id": "Ozawa-Yuta",
"name": {
"family": "Ozawa",
"given": "Yuta"
},
"orcid": "0000-0002-5895-0506"
},
{
"id": "Nonomura-Taku",
"name": {
"family": "Nonomura",
"given": "Taku"
},
"orcid": "0000-0001-7739-7104"
},
{
"id": "Asai-Keisuke",
"name": {
"family": "Asai",
"given": "Keisuke"
},
"orcid": "0000-0002-9330-4972"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Estimation of Time-Resolved Three-Dimensional Velocity Fields of Underexpanded Jets in Flapping Screech Mode",
"ispublished": "unpub",
"full_text_status": "public",
"note": "© 2022 by Chungil Lee/Tohoku University. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission.
",
"abstract": "\n
\n
A method for estimating time-resolved three-dimensional velocity fields from non-time-resolved particle image velocimetry (PIV) and time-resolved near-field acoustic data is proposed and evaluated on a screeching, underexpanded jet. Multi-time-delay modified linear stochastic estimation (MTD-mLSE) is applied to the reduced-order PIV data and the Fourier coefficients of the azimuthal modes of sound pressure data of eight microphones arranged in a ring. The dominant screech tone at a nozzle pressure ratio of 2.97 corresponds to the first asymmetric mode. Time-resolved three-dimensional velocity fields corresponding to this mode are estimated, and flow structures associated with the flapping oscillation are observed. The obtained result shows that the velocity fluctuations are large near the screech source location of the B (flapping) screech mode.
\n
\n
",
"date": "2022-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"place_of_pub": "Reston, VA",
"pagerange": "2022-3024",
"isbn": "978-1-62410-664-4",
"book_title": "28th AIAA/CEAS Aeroacoustics 2022 Conference",
"official_url": "https://authors.library.caltech.edu/records/73t32-zaw93",
"other_numbering_system": {
"items": [
{
"id": "2022-3024",
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"doi": "10.2514/6.2022-3024",
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"pub_year": "2022",
"author_list": "Lee, Chungil; Nishikori, Hiroki; et el."
},
{
"id": "https://authors.library.caltech.edu/records/2bcxf-5w302",
"eprint_id": 110202,
"eprint_status": "archive",
"datestamp": "2023-08-20 04:37:43",
"lastmod": "2023-10-20 23:14:30",
"type": "conference_item",
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"creators": {
"items": [
{
"id": "Br\u00e8s-Guillaume-A",
"name": {
"family": "Br\u00e8s",
"given": "Guillaume A."
},
"orcid": "0000-0003-2507-8659"
},
{
"id": "Yeung-Brandon",
"name": {
"family": "Yeung",
"given": "Brandon"
}
},
{
"id": "Schmidt-Oliver-T",
"name": {
"family": "Schmidt",
"given": "Oliver T."
},
"orcid": "0000-0002-7097-0235"
},
{
"id": "Ghassemi-Isfahani-Ata",
"name": {
"family": "Ghassemi Isfahani",
"given": "Ata"
}
},
{
"id": "Webb-Nathan-J",
"name": {
"family": "Webb",
"given": "Nathan J."
},
"orcid": "0000-0003-3900-1134"
},
{
"id": "Samimy-Mo",
"name": {
"family": "Samimy",
"given": "Mo"
},
"orcid": "0000-0003-0234-9655"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Towards large-eddy simulations of supersonic jets from twin rectangular nozzle with plasma actuation",
"ispublished": "unpub",
"full_text_status": "public",
"note": "\u00a9 2021 by the Authors. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 28 Jul 2021.",
"abstract": "Large-eddy simulation of a jet issuing from rectangular nozzles of aspect ratio 2 is performed. The nozzles are operating at their nominal design Mach number of 1.5. This operating condition and the geometry match those of the companion experiment conducted at Ohio State University. The preliminary results show good agreement with near-field and far-field noise measurements in terms of broadband levels and predictions of screech tone frequencies and amplitudes. In particular, the main noise radiation towards the aft angles and the overall sound pressure level directivity are within 1dB for most relevant frequencies and angles. For future simulations of active control, a numerical model of a localized arc filament plasma actuator is implemented and tested in a small test domain inside one of the nozzles. A grid resolution study is conducted to investigate the minimum grid resolution required for correct energy transport within the boundary layer.",
"date": "2021-08-02",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"place_of_pub": "Reston, VA",
"pagerange": "Art. No. 2021-2154",
"id_number": "CaltechAUTHORS:20210811-192602670",
"isbn": "978-1-62410-610-1",
"book_title": "AIAA Aviation 2021 Forum",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210811-192602670",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"other_numbering_system": {
"items": [
{
"id": "2021-2154",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2021-2154",
"resource_type": "conference_item",
"pub_year": "2021",
"author_list": "Br\u00e8s, Guillaume A.; Yeung, Brandon; et el."
},
{
"id": "https://authors.library.caltech.edu/records/3wzaf-84732",
"eprint_id": 97456,
"eprint_status": "archive",
"datestamp": "2023-08-19 08:14:32",
"lastmod": "2023-10-18 15:57:40",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "T."
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Rowley-C-W",
"name": {
"family": "Rowley",
"given": "C. W."
},
"orcid": "0000-0002-9099-5739"
},
{
"id": "Theofilis-V",
"name": {
"family": "Theofilis",
"given": "V."
}
}
]
},
"title": "Global Instabilities and Reduced-Order Models of Cavity Flow Oscillations",
"ispublished": "unpub",
"full_text_status": "public",
"date": "2019-07-31",
"date_type": "published",
"publisher": "Caltech Library",
"id_number": "CaltechAUTHORS:20190726-104730024",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190726-104730024",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"resource_type": "conference_item",
"pub_year": "2019",
"author_list": "Colonius, T.; Rowley, C. W.; et el."
},
{
"id": "https://authors.library.caltech.edu/records/atshr-qb711",
"eprint_id": 97450,
"eprint_status": "archive",
"datestamp": "2023-08-19 07:51:33",
"lastmod": "2023-10-18 15:57:22",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Tanguay-M",
"name": {
"family": "Tanguay",
"given": "Michel"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Numerical Simulation of Bubbly Cavitating Flow in Shock Wave Lithotripsy",
"ispublished": "unpub",
"full_text_status": "public",
"note": "We would like to thank the PPG investigators, particularly Murtuza Lokhandwalla and Mike Bailey for their insightful comments on this work as well as for sharing their experimental data. This paper is dedicated to the memory of Professor Brad Sturtevant, who provided the \"spark\" for this work as well as a myriad of useful suggestions; we miss him greatly. This work was supported by NIH under grant PO1 DK43881.\n\nAccepted Version - TanguayColonius2001.pdf
",
"abstract": "The bubbly cavitating flow generated by a lithotriptor is computed using an ensemble averaged two-phase flow model. The time-dependent, compressible flow computation is divided into two separate calculations: the refocusing of a spherical pulse by an ellipsoidal reflector, and the evolution of the steepening wave including the cavitating bubble cloud it generates. The first computation is single phase and is done in prolate spheroidal coordinates in order to have the surface of the ellipsoidal reflector aligned with the computation grid. The output of this simulation is then fed to the two-phase cylindrical coordinates domain. Preliminary results and qualitative comparison to experimental observation are presented.",
"date": "2019-07-31",
"date_type": "published",
"publisher": "Caltech Library",
"id_number": "CaltechAUTHORS:20190726-104729308",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190726-104729308",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "NIH",
"grant_number": "PO1 DK43881"
}
]
},
"primary_object": {
"basename": "TanguayColonius2001.pdf",
"url": "https://authors.library.caltech.edu/records/atshr-qb711/files/TanguayColonius2001.pdf"
},
"resource_type": "conference_item",
"pub_year": "2019",
"author_list": "Tanguay, Michel and Colonius, Tim"
},
{
"id": "https://authors.library.caltech.edu/records/xxcqb-b5t73",
"eprint_id": 96981,
"eprint_status": "archive",
"datestamp": "2023-08-19 15:54:10",
"lastmod": "2023-10-20 21:48:32",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Pickering-E-M",
"name": {
"family": "Pickering",
"given": "Ethan"
},
"orcid": "0000-0002-4485-6359"
},
{
"id": "Rigas-G",
"name": {
"family": "Rigas",
"given": "Georgios"
},
"orcid": "0000-0001-6692-6437"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Sipp-D",
"name": {
"family": "Sipp",
"given": "Denis"
},
"orcid": "0000-0002-2808-3886"
},
{
"id": "Schmidt-O-T",
"name": {
"family": "Schmidt",
"given": "Oliver T."
},
"orcid": "0000-0002-7097-0235"
}
]
},
"title": "Eddy viscosity for resolvent-based jet noise models",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 2019 by The Authors. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 18 May 2019. \n\nThis research was supported by a grant from the Office of Naval Research (grant No. N00014-16-1-2445) with Dr. Steven Martens as program manager. E.P. was supported by the Department of Defense (DoD) through the National Defense Science Engineering Graduate Fellowship (NDSEG) Program. The LES study was performed at Cascade Technologies, with support from ONR and NAVAIR SBIR project, under the supervision of Dr. John T. Spyropoulos. The main LES calculations were carried out on DoD HPC systems in ERDC DSRC.\n\nPublished - PickeringRigasSippEtAl2019.pdf
",
"abstract": "Response modes computed via linear resolvent analysis have shown promising results for qualitatively modeling both the hydrodynamic and acoustic fields in jets when compared to data-deduced modes from high-fidelity, large-eddy simulations (LES). For an improved quantitative prediction of the near- and far-field, the role of Reynolds stresses must also be considered. In this study, we propose a methodology to deduce an eddy-viscosity model that optimally captures the nonlinear forcing of resolvent modes. The methodology is based on the maximization of the projection between resolvent analysis and spectral proper orthogonal decomposition (SPOD) modes using a Lagrangian optimization framework. For a Mach 0.4 round, isothermal, turbulent jet, four methods are used to increase the projection coefficients: linear damping, spatially constant eddy-viscosity field, a turbulent kinetic energy derived viscosity field, and an optimized eddy-viscosity field. The resulting projection coefficients for the optimized eddy-viscosity field between SPOD and resolvent can be increased to over 90% for frequencies in the range St = 0.35\u22121 with significant improvements to St < 0.35. We find that the use of a frequency-independent turbulent kinetic energy turbulent viscosity model produces modes closely inline with optimal results, providing a preliminary eddy-viscosity resolvent model for jets.",
"date": "2019-05-18",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190709-092102524",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092102524",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Office of Naval Research (ONR)",
"grant_number": "N00014-16-1-2445"
},
{
"agency": "National Defense Science and Engineering Graduate (NDSEG) Fellowship"
},
{
"agency": "Naval Air Systems Command (NAVAIR)"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2019-2454",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2019-2454",
"primary_object": {
"basename": "PickeringRigasSippEtAl2019.pdf",
"url": "https://authors.library.caltech.edu/records/xxcqb-b5t73/files/PickeringRigasSippEtAl2019.pdf"
},
"resource_type": "conference_item",
"pub_year": "2019",
"author_list": "Pickering, Ethan; Rigas, Georgios; et el."
},
{
"id": "https://authors.library.caltech.edu/records/yj39b-ecz26",
"eprint_id": 96983,
"eprint_status": "archive",
"datestamp": "2023-08-19 15:54:15",
"lastmod": "2023-10-20 21:48:58",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Nogueira-P-A",
"name": {
"family": "Nogueira",
"given": "Petr\u00f4nio A. S."
}
},
{
"id": "Cavalieri-A-V-G",
"name": {
"family": "Cavalieri",
"given": "Andr\u00e9 V. G."
},
"orcid": "0000-0003-4283-0232"
},
{
"id": "Schmidt-O-T",
"name": {
"family": "Schmidt",
"given": "Oliver T."
},
"orcid": "0000-0002-7097-0235"
},
{
"id": "Jordan-P",
"name": {
"family": "Jordan",
"given": "Peter"
},
"orcid": "0000-0001-8576-5587"
},
{
"id": "Jaunet-V",
"name": {
"family": "Jaunet",
"given": "Vincent"
}
},
{
"id": "Pickering-E-M",
"name": {
"family": "Pickering",
"given": "Ethan"
},
"orcid": "0000-0002-4485-6359"
},
{
"id": "Rigas-G",
"name": {
"family": "Rigas",
"given": "Georgios"
},
"orcid": "0000-0001-6692-6437"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Resolvent-based analysis of streaks in turbulent jets",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 2019 by Petr\u00f4nio Nogueira, Andr\u00e9 Cavalieri, Oliver Schmidt, Peter Jordan, Vincent Jaunet, Ethan Pickering, Georgios Rigas, Tim Colonius. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 18 May 2019. \n\nPetr\u00f4nio Nogueira was funded by a CNPq scholarship. Andr\u00e9 Cavalieri acknowledges financial support by CNPq (grant number 310523/2017-6). This study was financed in part by the Coordena\u00e7\u00e3o de Aperfei\u00e7oamento de Pessoal de N\u00edvel Superior - Brasil (CAPES) - Finance Code 001.\n\nPublished - NogueiraCavalieriSchmidtEtAl2019.pdf
",
"abstract": "Large scale, elongated structures, similar those ones widely studied in wall-bounded flows, are also present in turbulent jets. Several characteristics of these streaks can be identified via reduced order models such as resolvent analysis. The present work involves a resolvent-based study of these structures in turbulent jets. We focus on obtaining the optimal forcing that generates these energetic coherent structures. Results are compared with experimental data post-processed using spectral proper orthogonal decomposition, allowing us to draw conclusions about the nature of the non-linear forcing, since the two analyses should provide equivalent results if this term is modelled as spatially white. By identifying streaks in a global framework, we expect to better understand the mechanism by which they are generated.",
"date": "2019-05-18",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190709-092102671",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092102671",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Conselho Nacional de Desenvolvimento Cient\u00edfico e Tecnol\u00f3gico (CNPq)",
"grant_number": "310523/2017-6"
},
{
"agency": "Coordena\u00e7\u00e3o de Aperfei\u00e7oamento de Pessoal de N\u00edvel Superior (CAPES)",
"grant_number": "001"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2019-2569",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2019-2569",
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"url": "https://authors.library.caltech.edu/records/yj39b-ecz26/files/NogueiraCavalieriSchmidtEtAl2019.pdf"
},
"resource_type": "conference_item",
"pub_year": "2019",
"author_list": "Nogueira, Petr\u00f4nio A. S.; Cavalieri, Andr\u00e9 V. G.; et el."
},
{
"id": "https://authors.library.caltech.edu/records/88z72-ng038",
"eprint_id": 96975,
"eprint_status": "archive",
"datestamp": "2023-08-19 15:54:05",
"lastmod": "2023-10-20 21:48:12",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Rigas-G",
"name": {
"family": "Rigas",
"given": "Georgios"
},
"orcid": "0000-0001-6692-6437"
},
{
"id": "Pickering-E-M",
"name": {
"family": "Pickering",
"given": "Ethan"
},
"orcid": "0000-0002-4485-6359"
},
{
"id": "Schmidt-O-T",
"name": {
"family": "Schmidt",
"given": "Oliver"
},
"orcid": "0000-0002-7097-0235"
},
{
"id": "Nogueira-P-A",
"name": {
"family": "Nogueira",
"given": "Petr\u00f4nio A. S."
}
},
{
"id": "Cavalieri-A-V-G",
"name": {
"family": "Cavalieri",
"given": "Andr\u00e9 V. G."
},
"orcid": "0000-0003-4283-0232"
},
{
"id": "Br\u00e8s-G-A",
"name": {
"family": "Br\u00e8s",
"given": "Guillaume A."
},
"orcid": "0000-0003-2507-8659"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Streaks and coherent structures in jets from round and serrated nozzles",
"ispublished": "unpub",
"full_text_status": "restricted",
"keywords": "Aeroacoustics",
"note": "\u00a9 2019 by the American Institute of Aeronautics and Astronautics, Inc. \n\nPublished Online: 18 May 2019. \n\nThis research was supported in part by a grant from the Office of Naval Research (grant No. N00014-16-1-2445) with Dr. Steven Martens as program manager. The LES study was performed at Cascade Technologies, with additional support from NAVAIR, under the supervision of Dr. John T. Spyropoulos. The main LES calculations were carried out on DoD HPC systems in ERDC DSRC. G.R. and T.C. also acknowledge the support of the Boeing Company through a Strategic Research and Development Relationship Agreement CT-BA-GTA-1.",
"abstract": "Hydrodynamic instabilities are directly related to large-scale coherent structures that are correlated with jet noise emission. Unravelling and accurately predicting their fundamental dynamics shows a promising direction for designing quieter jet engines. In this study, we analyze high-fidelity large-eddy simulation data of a turbulent Mach 0.4 round jet and a Mach 1.5 chevron jet. Using spectral proper orthogonal decomposition we identify, beyond the well-known Kelvin\u2013Helmoholtz and Orr mechanisms, elongated alternating streamwise streaks of high and low-speed fluid that have been associated with a non-modal lift-up effect in wall-bounded shear flows. In the global three-dimensional domain, the most energetic streaks manifest for azimuthal wavenumber m = 1 and frequency St \u2192 0. Furthermore, for the chevron jet, streaks and streamwise vortices appear due to the presence of the serrated nozzle, and they inherit the periodicity of the nozzle geometry. Finally, local (planar) spectral proper orthogonal decomposition is used to analyze the coherent structures of the chevron jet flow. Near the nozzle exit, antisymmetric and symmetric modes appear to be amplified and linked to the presence of the chevrons/streaks. Further downstream, the most energetic modes share similar characteristics to the ones observed in round jets.",
"date": "2019-05-18",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190709-092102068",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092102068",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Office of Naval Research (ONR)",
"grant_number": "N00014-16-1-2445"
},
{
"agency": "Naval Air Systems Command (NAVAIR)"
},
{
"agency": "Boeing Company Strategic Research and Development Relationship",
"grant_number": "CT-BA-GTA-1"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2019-2597",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2019-2597",
"resource_type": "conference_item",
"pub_year": "2019",
"author_list": "Rigas, Georgios; Pickering, Ethan; et el."
},
{
"id": "https://authors.library.caltech.edu/records/98rv2-x9015",
"eprint_id": 96972,
"eprint_status": "archive",
"datestamp": "2023-08-19 15:40:41",
"lastmod": "2023-10-20 21:47:03",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Schmidmayer-Kevin",
"name": {
"family": "Schmidmayer",
"given": "Kevin"
},
"orcid": "0000-0003-0444-3098"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "A comparative study on interface-capturing models and schemes to solve bubble dynamics and cavitation",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Bubble dynamics, Cavitation, Interface-capturing scheme, Multiphase flow, Compressible Flow",
"note": "Authors would like to thank Prof. Eric Johnsen, Dr. Shahaboddin Alahyari Beig and Mauro Rodriguez for fruitful discussions. This work was supported by the Office of Naval Research under grant N0014-18-1-2625.\n\nSubmitted - SchmidmayerColonius2019.pdf
",
"abstract": "In the context of simulation of bubble dynamics and cavitation, even the simple problem of the collapse of a spherical bubble is challenging to compute accurately with general, three-dimensional, interface-capturing schemes. Difficulties arise from both the physical model of the multicomponent fluid and the discretization scheme. Pathologies associated with each factor are identified and solutions to remedy specific issues are proposed.",
"date": "2019-05",
"date_type": "published",
"publisher": "Caltech Library",
"id_number": "CaltechAUTHORS:20190709-092100886",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092100886",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Office of Naval Research (ONR)",
"grant_number": "N0014-18-1-2625"
}
]
},
"primary_object": {
"basename": "SchmidmayerColonius2019.pdf",
"url": "https://authors.library.caltech.edu/records/98rv2-x9015/files/SchmidmayerColonius2019.pdf"
},
"resource_type": "conference_item",
"pub_year": "2019",
"author_list": "Schmidmayer, Kevin and Colonius, Tim"
},
{
"id": "https://authors.library.caltech.edu/records/hf1ft-76c23",
"eprint_id": 96961,
"eprint_status": "archive",
"datestamp": "2023-08-19 15:40:37",
"lastmod": "2023-10-20 21:46:38",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Bryngelson-S-H",
"name": {
"family": "Bryngelson",
"given": "Spencer H."
},
"orcid": "0000-0003-1750-7265"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "A comparison of ensemble- and volume-averaged bubbly flow models",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Bubble dynamics, cavitation, multiphase flow modeling, compressible flow",
"note": "The authors would like to thank Kevin Schmidmayer for fruitful discussions. This work was supported in part by the Office\nof Naval Research under grant N0014-17-1-2676.\n\nSubmitted - BryngelsonColonius2019.pdf
",
"abstract": "We compare volume- and ensemble-averaged bubbly flow models. Volume-averaging is a deterministic process for which bubbles are represented in a Lagrangian framework as advected particles, each sampled from a distribution of equilibrium bubble sizes. Ensemble-averaging instead uses mixture-averaged equations in an Eulerian reference frame for the associated bubble properties, each represented by bins of the equilibrium distribution. In both cases, bubbles are modeled as spherical with dynamics governed by the Keller-Miksis equation. Computationally, there are tradeoffs between these two approaches. Here, we simulate an acoustically excited dilute bubble screen and compare the computational efficiency of the two approaches.",
"date": "2019-05",
"date_type": "published",
"publisher": "Caltech Library",
"id_number": "CaltechAUTHORS:20190709-092059850",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092059850",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Office of Naval Research (ONR)",
"grant_number": "N0014-17-1-2676"
}
]
},
"primary_object": {
"basename": "BryngelsonColonius2019.pdf",
"url": "https://authors.library.caltech.edu/records/hf1ft-76c23/files/BryngelsonColonius2019.pdf"
},
"resource_type": "conference_item",
"pub_year": "2019",
"author_list": "Bryngelson, Spencer H. and Colonius, Tim"
},
{
"id": "https://authors.library.caltech.edu/records/n76h6-k0y88",
"eprint_id": 96954,
"eprint_status": "archive",
"datestamp": "2023-08-19 09:53:18",
"lastmod": "2023-10-20 21:46:16",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "da-Silva-A-F-C",
"name": {
"family": "da Silva",
"given": "Andre F."
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "A Bias-Aware EnKF Estimator for Aerodynamic Flows",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Fluid Dynamics",
"note": "\u00a9 2018 by Andre Fernando de Castro da Silva. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 24 Jun 2018. \n\nThis work has been supported in part by a grant from AFOSR (FA9550-14-1-0328) with Dr. Douglas Smith as program manager. A.F.C. da Silva would like to thank the Ministry of Education of Brazil (Capes Foundation) for its support through a Science without Borders scholarship (Grant number BEX 12966/13-4). The authors also acknowledge Prof. David Williams (Illinois Institute of Technology), Prof. Jeff Eldredge (University of California, Los Angeles) and Prof. Andrew Stuart (California Institute of Technology) for helpful discussions of this work.\n\nPublished - DaSilvaColonius2018b.pdf
",
"abstract": "Ensemble methods can integrate measurement data and CFD-based models to estimate the state of fluid systems in a robust and cost-efficient way. However, discretization errors can render numerical solutions a biased representation of reality. Left unaccounted for, biased forecast and observation models can lead to poor estimator performance. In this work, we propose a low-rank representation for the bias whose dynamics is represented by a colorednoise process. System state and bias parameters are simultaneously corrected on-line with the Ensemble Kalman Filter (EnKF) algorithm. The proposed methodology is demonstrated to achieve a 70% error reduction for the problem of estimating the state of the two-dimensional low-Re flow past a flat plate at high angle of attack using an ensemble of coarse-mesh simulations and pressure measurements at the surface of the body, compared to a bias-blind estimator. Strategies to determine the bias statistics and to deal with nonlinear observation functions in the context of ensemble methods are discussed.",
"date": "2018-06-24",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics (AIAA)",
"id_number": "CaltechAUTHORS:20190709-092059279",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092059279",
"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": "FA9550-14-1-0328"
},
{
"agency": "Coordena\u00e7\u00e3o de Aperfei\u00e7oamento de Pessoal de N\u00edvel Superior (CAPES)",
"grant_number": "BEX 12966/13-4"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2018-3225",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2018-3225",
"primary_object": {
"basename": "DaSilvaColonius2018b.pdf",
"url": "https://authors.library.caltech.edu/records/n76h6-k0y88/files/DaSilvaColonius2018b.pdf"
},
"resource_type": "conference_item",
"pub_year": "2018",
"author_list": "da Silva, Andre F. and Colonius, Tim"
},
{
"id": "https://authors.library.caltech.edu/records/dktqz-77584",
"eprint_id": 96946,
"eprint_status": "archive",
"datestamp": "2023-08-19 09:53:13",
"lastmod": "2023-10-20 21:38:41",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Antonialli-L-A",
"name": {
"family": "Antonialli",
"given": "Luigi A."
}
},
{
"id": "Cavalieri-A-V-G",
"name": {
"family": "Cavalieri",
"given": "Andr\u00e9 V. G."
},
"orcid": "0000-0003-4283-0232"
},
{
"id": "Schmidt-O-T",
"name": {
"family": "Schmidt",
"given": "Oliver T."
},
"orcid": "0000-0002-7097-0235"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Jordan-P",
"name": {
"family": "Jordan",
"given": "Peter"
},
"orcid": "0000-0001-8576-5587"
},
{
"id": "Towne-A",
"name": {
"family": "Towne",
"given": "Aaron"
},
"orcid": "0000-0002-7315-5375"
},
{
"id": "Br\u00e8s-G-A",
"name": {
"family": "Br\u00e8s",
"given": "Guillaume A."
},
"orcid": "0000-0003-2507-8659"
}
]
},
"title": "Amplitude scaling of turbulent-jet wavepackets",
"ispublished": "unpub",
"full_text_status": "restricted",
"note": "\u00a9 2018 American Institute of Aeronautics and Astronautics.\n\nPublished Online: 24 Jun 2018.",
"abstract": "Wavepackets modelling large-scale coherent structures are related to the peak noise radiation by subsonic jets. Such wavepacket models are well developed in the literature, and are often based on a linearization of the Navier-Stokes system; solutions of the resulting linear problem have a free amplitude, which can be obtained by comparison with experiments or simulations. In this work we determine amplitudes of turbulent-jet wavepackets by comparing large-eddy simulation (LES) data from Br`es et al. of a Mach 0.9 jet and fluctuation fields using the parabolized stability equations (PSE) model (Sasaki et al.). Projection of the leading mode from spectral proper orthogonal decomposition (SPOD), applied to the LES data, onto the PSE model solutions is a way to determine the free amplitude, and by analyzing such amplitudes for different Strouhal numbers and azimuthal modes of the turbulent jet, it is possible to notice a clear pattern of the scaling factor with varying St. Azimuthal wavenumbers m = 0, 1 and 2 show an exponential dependence of wavepacket amplitude with Strouhal number. This sheds light on how wavepackets amplitudes behave and how they are excited upstream.",
"date": "2018-06-24",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics (AIAA)",
"id_number": "CaltechAUTHORS:20190709-092058323",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092058323",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"other_numbering_system": {
"items": [
{
"id": "2018-2978",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2018-2978",
"resource_type": "conference_item",
"pub_year": "2018",
"author_list": "Antonialli, Luigi A.; Cavalieri, Andr\u00e9 V. G.; et el."
},
{
"id": "https://authors.library.caltech.edu/records/vwchx-gez79",
"eprint_id": 96962,
"eprint_status": "archive",
"datestamp": "2023-08-19 09:53:37",
"lastmod": "2023-10-20 21:46:41",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Br\u00e8s-G-A",
"name": {
"family": "Br\u00e8s",
"given": "Guillaume A."
},
"orcid": "0000-0003-2507-8659"
},
{
"id": "Bose-S-T",
"name": {
"family": "Bose",
"given": "Sanjeeb T."
}
},
{
"id": "Emory-Michael",
"name": {
"family": "Emory",
"given": "Michael"
}
},
{
"id": "Ham-Frank-E",
"name": {
"family": "Ham",
"given": "Frank E."
}
},
{
"id": "Schmidt-O-T",
"name": {
"family": "Schmidt",
"given": "Oliver T."
},
"orcid": "0000-0002-7097-0235"
},
{
"id": "Rigas-G",
"name": {
"family": "Rigas",
"given": "Georgios"
},
"orcid": "0000-0001-6692-6437"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Large-eddy simulations of co-annular turbulent jet using a Voronoi-based mesh generation framework",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 2018 by The Authors. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 24 Jun 2018. \n\nThe LES studies are supported in part by NAVAIR SBIR projects, under the supervision of Dr. John T. Spyropoulos and by ONR grant N00014-16-1-2445. The main calculations were carried out at DoD HPCMP supercomputer system \"Onyx\" in ERDC DSRC. The authors would like to thanks Prof. Kris Ahuja, Aharon Karon & Nick Breen of Georgia Institute of Technology, for providing the nozzle geometry and experimental data for the co-annular jet.\n\nPublished - BresBoseEmoryEtAl2018.pdf
",
"abstract": "Large eddy simulations are performed for a cold ideally-expanded dual-stream jet issued from cylindrical co-axial nozzles, with supersonic primary stream (Mach number M_1 = 1.55) and subsonic secondary stream (M_2 = 0.9). The geometry includes the internal screw holes used to fasten the two nozzles together and to the plenum chamber. These slanted cylindrical holes over which the secondary stream flows were not covered in the experiment and were seamlessly captured in the computational mesh thanks to a novel grid generation paradigm based on the computation of Voronoi diagrams. A simulation with the screw holes covered is also performed and the preliminary results tends to indicate that these features have minimal impact on the flow and acoustic fields for the present operating conditions. As expected, the present dual-stream configuration with subsonic annular stream surrounding the primary supersonic stream features a reduced shear-layer growth, a longer potential core and a lack of strong Mach wave radiation. A long LES database is currently being collected for analysis and modeling of wavepackets and noise sources in such complex turbulent jets.",
"date": "2018-06-24",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics (AIAA)",
"id_number": "CaltechAUTHORS:20190709-092059954",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092059954",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Office of Naval Research (ONR)",
"grant_number": "N00014-16-1-2445"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2018-3302",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2018-3302",
"primary_object": {
"basename": "BresBoseEmoryEtAl2018.pdf",
"url": "https://authors.library.caltech.edu/records/vwchx-gez79/files/BresBoseEmoryEtAl2018.pdf"
},
"resource_type": "conference_item",
"pub_year": "2018",
"author_list": "Br\u00e8s, Guillaume A.; Bose, Sanjeeb T.; et el."
},
{
"id": "https://authors.library.caltech.edu/records/wxgfm-r6z29",
"eprint_id": 96979,
"eprint_status": "archive",
"datestamp": "2023-08-19 08:48:55",
"lastmod": "2023-10-20 21:53:08",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Pishchalnikov-Y-A",
"name": {
"family": "Pishchalnikov",
"given": "Yuri A."
}
},
{
"id": "Behnke-Parks-W",
"name": {
"family": "Behnke-Parks",
"given": "William"
}
},
{
"id": "Mellema-M",
"name": {
"family": "Mellema",
"given": "Matt"
}
},
{
"id": "Hopcroft-M",
"name": {
"family": "Hopcroft",
"given": "Matt"
}
},
{
"id": "Luong-Alice",
"name": {
"family": "Luong",
"given": "Alice"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Maeda-Kazuki",
"name": {
"family": "Maeda",
"given": "Kazuki"
},
"orcid": "0000-0002-5729-6194"
},
{
"id": "Morrison-Kyle",
"name": {
"family": "Morrison",
"given": "Kyle"
}
},
{
"id": "Laser-D",
"name": {
"family": "Laser",
"given": "Daniel"
}
}
]
},
"title": "Urinary stone erosion and fragmentation under low-intensity quasi-collimated ultrasound using gas-filled microbubbles with stone-targeting lipid shells",
"ispublished": "unpub",
"full_text_status": "public",
"note": "\u00a9 2018 Acoustical Society of America. \n\nPublished Online: 17 April 2018.",
"abstract": "Urinary stone lithotripsy critically depends on the presence of cavitation nuclei at the stone surface. We hypothesized that introduction of stone-targeting microbubbles could increase cavitation activity at a stone surface sufficiently to allow stone erosion and fragmentation at peak negative pressures much lower than in acoustic energy-based urinary stone interventions with induced cavitation nuclei alone. Gas-filled microbubbles were produced with calcium-binding moieties incorporated into an encapsulating lipid shell. Stone surface coverage with these targeting microbubbles was found to approach an optimal (considering microbubble expansion during insonation) range of 5\u201315% with incubation times of three minutes or less. Using high-speed photomicroscopy, we observe bound microbubbles expanding 10- to 30-fold under insonation with quasi-collimated sources at mechanical indexes below 1.9. For observed stand-off parameters in the range of 0.2\u20130.6, the modeled collapse-generated shockwaves exceed 100 MPa. In swine model studies with these targeting microbubbles, stone fragmentation into passable fragments occurs with treatment times around 30 minutes, while post-treatment examination of ureters and kidneys shows no evidence of urothelium damage or renal parenchymal hemorrhage. The stone-targeting microbubbles reported on here have formed the basis for a new non-invasive urinary stone treatment which recently entered human clinical trials.",
"date": "2018-04-17",
"date_type": "published",
"id_number": "CaltechAUTHORS:20190709-092102360",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092102360",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"doi": "10.1121/1.5036106",
"resource_type": "conference_item",
"pub_year": "2018",
"author_list": "Pishchalnikov, Yuri A.; Behnke-Parks, William; et el."
},
{
"id": "https://authors.library.caltech.edu/records/4bwxh-z4k62",
"eprint_id": 96955,
"eprint_status": "archive",
"datestamp": "2023-08-19 07:18:46",
"lastmod": "2023-10-20 21:46:22",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Darakananda-D",
"name": {
"family": "Darakananda",
"given": "Darwin"
}
},
{
"id": "Eldredge-J-D",
"name": {
"family": "Eldredge",
"given": "Jeff"
}
},
{
"id": "da-Silva-A-F-C",
"name": {
"family": "da Silva",
"given": "Andre"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Williams-D-R",
"name": {
"family": "Williams",
"given": "David R."
}
}
]
},
"title": "EnKF-Based Dynamic Estimation of Separated Flows with a Low-Order Vortex Model",
"ispublished": "unpub",
"full_text_status": "restricted",
"note": "\u00a9 2018 American Institute of Aeronautics and Astronautics. \n\nPublished Online: 7 Jan 2018. \n\nSupport by the U.S. Air Force Office of Scientific Research (FA9550-14-1-0328) with program manager Dr. Douglas Smith is gratefully acknowledged.",
"abstract": "A data-driven vortex model of the unsteady aerodynamics of a two-dimensional separated flow is constructed. The vortex model relies on a standard collection of regularized vortex elements that interact mutually and with an infinitely-thin flat plate. In order to maintain a low-dimensional representation, with fewer than O(100) degrees of freedom, a novel aggregation procedure is developed and utilized in which vortex elements are coalesced at each time step. A flow state vector, composed of vortex elements properties as well as the critical leading-edge suction parameter of Ramesh and Gopalarathnam (J. Fluid Mech., 2014), is advanced within an ensemble Kalman filter (EnKF) framework. In this framework, surface pressure measurements, sampled from a truth case, are used to correct the states of an ensemble of randomly-initiated vortex element models. The estimation algorithm is applied to several scenarios of a flat plate impulsively started at 20 degrees angle of attack at Reynolds number 500, in which the truth case comprises a high-fidelity Navier\u2013Stokes simulation. The algorithm provides a good estimate of the flow as well as the aerodynamic force in both the baseline undisturbed case (a separated flow) as well as in the presence of one or more incident gusts, despite lack of a priori knowledge of the incident gust character.",
"date": "2018-01-07",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics (AIAA)",
"id_number": "CaltechAUTHORS:20190709-092059362",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092059362",
"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": "FA9550-14-1-0328"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2018-0811",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2018-0811",
"resource_type": "conference_item",
"pub_year": "2018",
"author_list": "Darakananda, Darwin; Eldredge, Jeff; et el."
},
{
"id": "https://authors.library.caltech.edu/records/7agx4-byg45",
"eprint_id": 96953,
"eprint_status": "archive",
"datestamp": "2023-08-19 04:01:17",
"lastmod": "2023-10-23 15:10:00",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Goza-A",
"name": {
"family": "Goza",
"given": "Andres"
},
"orcid": "0000-0002-9372-7713"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "A global mode analysis of flapping flags",
"ispublished": "unpub",
"full_text_status": "public",
"note": "This research was partially supported by a grant from the Jet Propulsion Laboratory (Grant No. 1492185) and by a grant from the Air Force Office of Scientific Research (AFOSR FA9550-14-1-0328). The first author gratefully acknowledges funding from the National Science Foundation Graduate Research Fellowship Program (Grant No. DGE-1144469). We gratefully acknowledge Professor John Sader for helpful discussions on inverted flags.\n\nPublished - 333.pdf
",
"abstract": "We perform a global stability analysis of a flapping flag in the conventional configuration, in which the flag is pinned or clamped at its leading edge, and in the inverted configuration, in which the flag is clamped at its trailing edge. Specifically, we consider fully coupled fluid-structure interaction for two-dimensional flags at low Reynolds numbers. For the conventional configuration, we show that the unstable global modes accurately predict the onset of flapping for a wide range of mass and stiffness ratios. For the inverted configuration, we identify a stable deformed equilibrium state and demonstrate that as the flag becomes less stiff, this equilibrium undergoes a supercritical Hopf bifurcation in which the least damped mode transitions to instability. Previous stability analyses of inverted flags computed the leading mode of the undeformed equilibrium state and found it to be a zero-frequency (non-flapping) mode, which does not reflect the inherent flapping behavior. We show that the leading mode of the deformed equilibrium is associated with a non-zero frequency, and therefore offers a mechanism for flapping. We emphasize that for both configurations the global modes are obtained from the fully-coupled flow-flag system, and therefore reveal both the most dominant flag shapes and the corresponding flow structures that are pivotal to flag flapping behavior.",
"date": "2017-07",
"date_type": "published",
"publisher": "Begel House Inc.",
"id_number": "CaltechAUTHORS:20190709-092059193",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092059193",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "JPL",
"grant_number": "1492185"
},
{
"agency": "Air Force Office of Scientific Research (AFOSR)",
"grant_number": "FA9550-14-1-0328"
},
{
"agency": "NSF",
"grant_number": "DGE-1144469"
}
]
},
"primary_object": {
"basename": "333.pdf",
"url": "https://authors.library.caltech.edu/records/7agx4-byg45/files/333.pdf"
},
"resource_type": "conference_item",
"pub_year": "2017",
"author_list": "Goza, Andres and Colonius, Tim"
},
{
"id": "https://authors.library.caltech.edu/records/7abkv-d0937",
"eprint_id": 96985,
"eprint_status": "archive",
"datestamp": "2023-08-21 21:14:31",
"lastmod": "2023-10-23 16:04:33",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "McAteer-J-A",
"name": {
"family": "McAteer",
"given": "James"
}
},
{
"id": "Evan-A-P",
"name": {
"family": "Evan",
"given": "Andrew P."
}
},
{
"id": "Lingeman-J-E",
"name": {
"family": "Lingeman",
"given": "James E."
}
},
{
"id": "Willis-L-R",
"name": {
"family": "Willis",
"given": "Lynn R."
}
},
{
"id": "Blomgren-P-M",
"name": {
"family": "Blomgren",
"given": "Philip M."
}
},
{
"id": "Williams-J-C-Jr",
"name": {
"family": "Williams",
"given": "James C."
}
},
{
"id": "Handa-Rajash",
"name": {
"family": "Handa",
"given": "Rajash"
}
},
{
"id": "Connors-B-A",
"name": {
"family": "Connors",
"given": "Bret A."
}
},
{
"id": "Crum-L-A",
"name": {
"family": "Crum",
"given": "Lawrence"
}
},
{
"id": "Bailey-M-R",
"name": {
"family": "Bailey",
"given": "Michael"
}
},
{
"id": "Matula-Tom",
"name": {
"family": "Matula",
"given": "Tom"
}
},
{
"id": "Khokhlova-Vera",
"name": {
"family": "Khokhlova",
"given": "Vera A."
}
},
{
"id": "Sapozhnikov-O-A",
"name": {
"family": "Sapozhnikov",
"given": "Oleg A."
}
},
{
"id": "Cleveland-R-O",
"name": {
"family": "Cleveland",
"given": "Robin"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Pishchalnikov-Y-A",
"name": {
"family": "Pishchalnikov",
"given": "Yuri A."
}
}
]
},
"title": "Ed Carstensen, advisor and mentor to the shockwave lithotripsy program project group",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Diseases and conditions; Organs; Physical acoustics; Ultrasound; Shock waves; Animal model; Medical diagnosis",
"note": "\u00a9 Acoustical Society of America. \n\nPublished Online: 10 June 2017. \n\nWork supported by NIH-DK43881.",
"abstract": "In the 1980s shockwave lithotripsy emerged as a revolutionary advancement for the treatment of kidney stones. Initial studies with patients showed SWL to be highly effective. The technology was elegant, outcomes exceptionally positive and early tests suggested treatment was safe. As experience with SWL grew, limitations surfaced. A key finding was that SWs have the potential to induce significant trauma to the kidney. Our group convinced the NIH it was time to conduct a rigorous assessment to characterize the adverse effects of SWL and determine the mechanisms of SW action in stone breakage and tissue injury. The NIH Program Project Grant mechanism mandated we establish a panel of external advisors to help guide our work. We needed expertise in physical acoustics, cavitation and animal models of ultrasound exposure. We wanted a leading expert. We were extremely fortunate to land Ed Carstensen. Ed worked with us for nearly 15 years, well into our third renewal cycle. He was a brilliant scientist, a man dedicated to the highest standards of conduct in research. Ed taught us a great deal, he inspired by example and had an exceptional influence on our work and on the greater field of lithotripsy research.",
"date": "2017-06-10",
"date_type": "published",
"publisher": "ASA",
"id_number": "CaltechAUTHORS:20190709-092102823",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092102823",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "NIH",
"grant_number": "DK43881"
}
]
},
"doi": "10.1121/1.4988642",
"resource_type": "conference_item",
"pub_year": "2017",
"author_list": "McAteer, James; Evan, Andrew P.; et el."
},
{
"id": "https://authors.library.caltech.edu/records/qrbvv-tcw85",
"eprint_id": 96949,
"eprint_status": "archive",
"datestamp": "2023-08-21 21:13:44",
"lastmod": "2023-10-23 16:06:25",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Maeda-Kazuki",
"name": {
"family": "Maeda",
"given": "Kazuki"
},
"orcid": "0000-0002-5729-6194"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Kreider-W",
"name": {
"family": "Kreider",
"given": "Wayne"
}
},
{
"id": "Maxwell-A-D",
"name": {
"family": "Maxwell",
"given": "Adam D."
}
},
{
"id": "Bailey-M-R",
"name": {
"family": "Bailey",
"given": "Michael"
}
}
]
},
"title": "Quantification of the shielding of kidney stones by bubble clouds during burst wave lithotripsy",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Acoustical properties; Acoustic signal processing; Energy flux; Organs; Hydrophone; Ultrasound; Medical diagnosis",
"note": "\u00a9 2017 Acoustical Society of America. \n\nPublished Online: 09 June 2017. \n\nWork supported by NIH 2P01-DK043881.",
"abstract": "Bubble clouds can shield kidney stones from insonification, and limit stone breakage during burst-wave lithotripsy (BWL), a recently proposed technique that uses focused ultrasound pulses with an amplitude of O(1-10) MPa and frequency of O(0.1) MHz. We use numerical simulations to quantify the magnitude of such shielding. In the simulations, we solve for the radial evolution of Lagrangian bubbles coupled to a compressible fluid using volume-averaging techniques. The resulting equations are discretized on an Eulerian grid. In particular, we quantify the reduction in acoustic energy flux incident on a rigid, plane wall that models the stone surface. We consider a burst wave with an amplitude of 6 MPa and a bubble cloud of diameter O(1) mm. The size distribution of nuclei, the number density of bubbles, and the distance of the cloud from the wall are varied, We show that a cloud containing O(10) bubbles with a diameter of O(10) um can reduce the total energy flux by more than 50%, largely independent of distribution of nuclei. Finally, we compare the simulation results with high-speed images and hydrophone measurements of bubble clouds from companion experiments.",
"date": "2017-06-09",
"date_type": "published",
"publisher": "Acoustical Society of America",
"id_number": "CaltechAUTHORS:20190709-092058839",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092058839",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "NIH",
"grant_number": "2P01-DK043881"
}
]
},
"doi": "10.1121/1.4987968",
"resource_type": "conference_item",
"pub_year": "2017",
"author_list": "Maeda, Kazuki; Colonius, Tim; et el."
},
{
"id": "https://authors.library.caltech.edu/records/a9827-z2533",
"eprint_id": 96968,
"eprint_status": "archive",
"datestamp": "2023-08-19 03:36:51",
"lastmod": "2023-10-20 21:46:55",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "da-Silva-A-F-C",
"name": {
"family": "da Silva",
"given": "Andre F. C."
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "An EnKF-Based Flow State Estimator for Aerodynamic Flows",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Theoretical Fluid Mechanics",
"note": "\u00a9 2017 American Institute of Aeronautics and Astronautics. \n\nPublished Online: 2 Jun 2017. \n\nThis work has been supported in part by a grant from AFOSR (FA9550-14-1-0328) with Dr. Douglas Smith as program manager. A.F.C. da Silva would like to thank the Ministry of Education of Brazil (Capes Foundation) for its support through a Science without Borders scholarship (Grant number BEX 12966/13-4). The authors also acknowledge Prof. Andrew Stuart, Prof. David Williams and Prof. Jeff Eldredge for helpful discussions of this work.\n\nSubmitted - SilvaColonius2017.pdf
",
"abstract": "Regardless of plant model, robust flow estimation based on limited measurements remains a major obstacle to successful flow control applications. Aiming to combine the robustness of a high-dimensional representation of the dynamics with the cost efficiency of a low-order approximation of the state covariance matrix, a flow state estimator based on the Ensemble Kalman Filter (EnKF) is applied to two-dimensional flow past a cylinder and an airfoil at high angle of attack and low Reynolds number. For the development purposes, we use the numerical algorithm as both the estimator and as a surrogate for the measurements. Estimation is successful using a reduced number of either pressure sensors on the surface of the body or sparsely placed velocity probes in the wake. Because the most relevant features of these flows is restricted to a low-dimensional subspace/manifold of the state space, asymptotic behavior of the estimator is shown to be achieved with a small ensemble size. The relative importance of each sensor location is evaluated by analyzing how they influence the estimated flow field. Covariance inflation is used to enhance the estimator performance in the presence of unmodeled free stream perturbations. A combination of parametric modeling and augmented state methodology is used to successfully estimate the forces on immersed bodies.",
"date": "2017-06-07",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190709-092100532",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092100532",
"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": "FA9550-14-1-0328"
},
{
"agency": "Coordena\u00e7\u00e3o de Aperfei\u00e7oamento de Pessoal de N\u00edvel Superior (CAPES)",
"grant_number": "BEX 12966/13-4"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2017-3483",
"name": "AIAA"
}
]
},
"doi": "10.2514/6.2017-3483",
"primary_object": {
"basename": "SilvaColonius2017.pdf",
"url": "https://authors.library.caltech.edu/records/a9827-z2533/files/SilvaColonius2017.pdf"
},
"resource_type": "conference_item",
"pub_year": "2017",
"author_list": "da Silva, Andre F. C. and Colonius, Tim"
},
{
"id": "https://authors.library.caltech.edu/records/9wndm-trf85",
"eprint_id": 96951,
"eprint_status": "archive",
"datestamp": "2023-08-19 03:35:08",
"lastmod": "2023-10-20 21:38:49",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Kleine-V-G",
"name": {
"family": "Kleine",
"given": "Vitor G."
}
},
{
"id": "Sasaki-Kenzo",
"name": {
"family": "Sasaki",
"given": "Kenzo"
},
"orcid": "0000-0002-3347-4996"
},
{
"id": "Cavalieri-A-V-G",
"name": {
"family": "Cavalieri",
"given": "Andr\u00e9 V. G."
},
"orcid": "0000-0003-4283-0232"
},
{
"id": "Br\u00e8s-G-A",
"name": {
"family": "Br\u00e8s",
"given": "Guillaume A."
},
"orcid": "0000-0003-2507-8659"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Evaluation of PSE as a Model for Supersonic Jet Using Transfer Functions",
"ispublished": "unpub",
"full_text_status": "public",
"note": "\u00a9 2017 by Andr\u00e9 Valdetaro Gomes Cavalieri. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 2 Jun 2017. \n\nThis work has been funded by CNPq (grant number 444796/2014-2). A. Cavalieri was supported by a CNPq research scholarship. Kenzo Sasaki acknowledges the financial support from Capes via a PhD scholarship.\n\nPublished - KleineSasakiCavalieriEtAl2017.pdf
",
"abstract": "Parabolized Stability Equations (PSE) have been shown to model wavepackets and, consequently, the near field of turbulent jets with reasonable accuracy. Because of these capabilities, PSE is a promising reduced-order model to derive control laws that could be employed to reduce the sound generation of a jet. The purpose of this work is to apply PSE to obtain time-domain transfer functions that could estimate both the fluid-dynamic and the acoustic fields of a supersonic jet. The results of this model were compared to results obtained from a database of a well-validated large-eddy simulation of a supersonic jet.\n\nBased on the unsteady pressure data at a input position, the time-domain pressure field was estimated using transfer functions obtained using PSE and an empirical method based on the LES data. The prediction scheme employed is a single-input-single-output (SISO), linear model. The unsteady pressure predicted by PSE showed good agreement with the LES results, especially if the input position is outside the mixing layer. For this region, the prediction capabilities of PSE are comparable to those of empirical transfer functions. The agreement is good even for output points taken in the acoustic field, showing that it is possible to estimate the time-domain behaviour of Mach-wave radiation using transfer functions.\n\nThis indicates that PSE could not only be used to predict the sound generation, but also to open up new potentialities to attenuate noise by means of closed-loop control of the flow. The exploration of the regions where the method displayed good agreement, presented in this work, can guide the positioning of sensors and actuators for experimental implementation of closed-loop control in a jet.",
"date": "2017-06-02",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190709-092059023",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092059023",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Conselho Nacional de Desenvolvimento Cient\u00edfico e Tecnol\u00f3gico (CNPq)",
"grant_number": "444796/2014-2"
},
{
"agency": "Coordena\u00e7\u00e3o de Aperfei\u00e7oamento de Pessoal de N\u00edvel Superior (CAPES)"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2017-4194",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2017-4194",
"primary_object": {
"basename": "KleineSasakiCavalieriEtAl2017.pdf",
"url": "https://authors.library.caltech.edu/records/9wndm-trf85/files/KleineSasakiCavalieriEtAl2017.pdf"
},
"resource_type": "conference_item",
"pub_year": "2017",
"author_list": "Kleine, Vitor G.; Sasaki, Kenzo; et el."
},
{
"id": "https://authors.library.caltech.edu/records/dsj7w-7kr08",
"eprint_id": 96984,
"eprint_status": "archive",
"datestamp": "2023-08-19 03:35:18",
"lastmod": "2023-10-20 21:49:01",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Mengaldo-Gianmarco",
"name": {
"family": "Mengaldo",
"given": "Gianmarco"
},
"orcid": "0000-0002-0157-5477"
},
{
"id": "Liska-Sebastian",
"name": {
"family": "Liska",
"given": "Sebastian"
},
"orcid": "0000-0003-4139-9364"
},
{
"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": "Jardin-Thierry",
"name": {
"family": "Jardin",
"given": "Thierry"
}
}
]
},
"title": "Immersed Boundary Lattice Green Function methods for External Aerodynamics",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Computational Fluid Dynamics",
"note": "\u00a9 2017 American Institute of Aeronautics and Astronautics. \n\nPublished Online: 2 Jun 2017. \n\nThis research was supported in part by a grant from ONR (N00014-16-1-2734) under the direction of Mr. Ken Iwanski.\n\nSubmitted - MengaldoLiskaYuEtAl2017.pdf
",
"abstract": "In this paper, we document the capabilities of a novel numerical approach \u2014 the immersed boundary lattice Green's function (IBLGF) method \u2014 to simulate external incompressible flows over complex geometries. This new approach is built upon the immersed boundary method and lattice Green's functions to solve the incompressible Navier-Stokes equations. We show that the combination of these two concepts allows the construction of an efficient and robust numerical framework for the direct numerical and large-eddy simulation of external aerodynamic problems at moderate to high-Reynolds numbers.",
"date": "2017-06-02",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190709-092102731",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092102731",
"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"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2017-3621",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2017-3621",
"primary_object": {
"basename": "MengaldoLiskaYuEtAl2017.pdf",
"url": "https://authors.library.caltech.edu/records/dsj7w-7kr08/files/MengaldoLiskaYuEtAl2017.pdf"
},
"resource_type": "conference_item",
"pub_year": "2017",
"author_list": "Mengaldo, Gianmarco; Liska, Sebastian; et el."
},
{
"id": "https://authors.library.caltech.edu/records/kw7v0-nn045",
"eprint_id": 96974,
"eprint_status": "archive",
"datestamp": "2023-08-19 03:35:13",
"lastmod": "2023-10-20 21:48:05",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Rigas-G",
"name": {
"family": "Rigas",
"given": "Georgios"
},
"orcid": "0000-0001-6692-6437"
},
{
"id": "Schmidt-O-T",
"name": {
"family": "Schmidt",
"given": "Oliver T."
},
"orcid": "0000-0002-7097-0235"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Br\u00e8s-G-A",
"name": {
"family": "Br\u00e8s",
"given": "Guillaume A."
},
"orcid": "0000-0003-2507-8659"
}
]
},
"title": "One Way Navier-Stokes and resolvent analysis for modeling coherent structures in a supersonic turbulent jet",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 2017 American Institute of Aeronautics and Astronautics. \n\nPublished Online: 2 Jun 2017. \n\nThis research was supported in part by a grant from the Office of Naval Research (grant No. N00014-16-1-2445) with Dr. Knox Millsaps as program manager. The LES study was performed at Cascade Technologies, with support from ONR and NAVAIR SBIR project, under the supervision of Dr. John T. Spyropoulos. The main LES calculations were carried out on DoD HPC systems in ERDC DSRC. O.S. was also supported in part by DFG grant No. SCHM 3114/1-1. G.R. and T.C. also acknowledge the support of the Boeing Company through a Strategic Research and Development Relationship Agreement CT-BA-GTA-1.\n\nSubmitted - RigasSchmidtColoniusEtAl2017.pdf
",
"abstract": "A linear analysis of the mean flow of an isothermal ideally-expanded Mach 1.5 turbulent jet is conducted. Optimal response modes describing the fluctuating hydrodynamic and acoustic fields are obtained in a computationally efficient way by spatially marching the linearized One-Way Navier-Stokes equations. For this purpose, an adjoint-based optimization framework is proposed and demonstrated for calculating optimal boundary conditions and optimal volumetric forcing. The optimal modes are validated against modes obtained in terms of global resolvent analysis. Two scenarios are considered in the present analysis. In the first case, no restrictions are applied to the spatial forcing distribution. In the second scenario, the forcing is restricted to the nozzle plane. The resulting optimal and suboptimal modes are compared to spectral proper orthogonal modes obtained from a high-fidelity large eddy simulation. The implications of these observations are discussed in detail.",
"date": "2017-06-02",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190709-092101985",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092101985",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Office of Naval Research (ONR)",
"grant_number": "N00014-16-1-2445"
},
{
"agency": "Naval Air Systems Command (NAVAIR)"
},
{
"agency": "Deutsche Forschungsgemeinschaft (DFG)",
"grant_number": "SCHM 3114/1-1"
},
{
"agency": "Boeing Company Strategic Research and Development Relationship",
"grant_number": "CT-BA-GTA-1"
}
]
},
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"id": "2017-4046",
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"items": [
{
"id": "An-Xuanhong",
"name": {
"family": "An",
"given": "Xuanhong"
}
},
{
"id": "Williams-D-R",
"name": {
"family": "Williams",
"given": "David R."
}
},
{
"id": "de-Castro-da-Silva-A-F",
"name": {
"family": "de Castro da Silva",
"given": "Andr\u00e9 Fernando"
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{
"id": "Colonius-T",
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},
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},
{
"id": "Eldredge-J-D",
"name": {
"family": "Eldredge",
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}
}
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},
"title": "Response of the Separated Flow over an Airfoil to a Short-Time Actuator Burst",
"ispublished": "unpub",
"full_text_status": "public",
"note": "\u00a9 2017 American Institute of Aeronautics and Astronautics.\n\nPublished Online: 2 Jun 2017.\n\nSupport by the U.S. Air Force Office of Scientific Research (FA9550-14-1-0328) with program manager Dr. Douglas Smith is gratefully acknowledged.\n\nSubmitted - AnWilliamsSilvaEtAl2017.pdf
",
"abstract": "Experimental measurements of the flow structure evolving in the separated flow over an NACA 0009 wing at 12\u00b0 angle of attack were obtained with particle image velocimetry, surface pressures, and force transducer measurements of the lift coefficient and pitching moment coefficient. Phase-averaged two-dimensional velocity field measurements provide details of the separated shear layer evolution following a four-pulse burst sequence from a synthetic jet actuator. The flow field development is quite similar to the observations made by Brzozowski, et al. (2010), who used a pulsed-combustion actuator that is orders of magnitude stronger than the synthetic jet. Proper orthogonal decomposition of the PIV data sets showed that the combination of the time-varying coefficients modes 1 and 2 correlate with the negative of the lift coefficient response. The surface pressure signals were correlated with the roll up and convection of the large-scale vortex structure that follows the actuator burst input. A spatially localized region of high pressure occurs below and slightly behind a \"kink\" that forms in the shear layer. A localized region of high surface pressure that follows the kinked region correlates with the lift reversal that occurs within 2.0t^+ after the burst signal was triggered.",
"date": "2017-06-02",
"date_type": "published",
"publisher": "american institute of aeronautics and astronautics",
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"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
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"items": [
{
"agency": "Air Force Office of Scientific Research (AFOSR)",
"grant_number": "FA9550-14-1-0328"
}
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"creators": {
"items": [
{
"id": "Bailey-M-R",
"name": {
"family": "Bailey",
"given": "Michael"
}
},
{
"id": "Simon-Julianna-C",
"name": {
"family": "Simon",
"given": "Julianna C."
}
},
{
"id": "Kreider-W",
"name": {
"family": "Kreider",
"given": "Wayne"
}
},
{
"id": "Dunmire-Barbrina",
"name": {
"family": "Dunmire",
"given": "Barbrina"
}
},
{
"id": "Crum-L-A",
"name": {
"family": "Crum",
"given": "Lawrence"
}
},
{
"id": "Maxwell-A-D",
"name": {
"family": "Maxwell",
"given": "Adam D."
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{
"id": "Khokhlova-Vera",
"name": {
"family": "Khokhlova",
"given": "Vera"
}
},
{
"id": "Sapozhnikov-O-A",
"name": {
"family": "Sapozhnikov",
"given": "Oleg A."
}
},
{
"id": "Cleveland-R-O",
"name": {
"family": "Cleveland",
"given": "Robin"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Lingeman-J-E",
"name": {
"family": "Lingeman",
"given": "James E."
}
},
{
"id": "McAteer-J-A",
"name": {
"family": "McAteer",
"given": "James"
}
},
{
"id": "Williams-J-C-Jr",
"name": {
"family": "Williams",
"given": "James C."
}
},
{
"id": "Freund-J-B",
"name": {
"family": "Freund",
"given": "Jonathan"
}
}
]
},
"title": "Innovative strategies for improved outcomes in nephrolithiasis",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Metrology; Chemical compounds and components; Ultrasound; Computer simulation; Medical diagnosis",
"note": "\u00a9 2017 Acoustical Society of America. \n\nPublished Online: 10 June 2017. \n\nWork supported by NIH P01DK043881, K01DK104854, R01EB007643, and NSBRI through NASA NCC 9-58.",
"abstract": "Edwin Carstensen, Ph.D., was an advisor of NIH NIDDK Program Project Grant DK043881, created to investigate shock wave lithotripsy (SWL). We now develop solutions to improve all aspects of the management of stone disease. Our goal in this paper is to report progress built on Dr. Cartsensen's advice and inspiration. The work ranges from numerical simulation to clinical trials and from device development to bioeffects and metrology. Much of our work involves bubbles and cavitation. This work has contributed to the body of knowledge defining limits for the safe use of ultrasound which Dr. Carstensen worked hard to establish. Specifically, an update will be given on the development of ultrasound to image, fragment, trap, and reposition stones. In particular, we demonstrated bubbles contribute to the twinkling artifact used by NASA and others to image stones, and we drew on Dr. Carstensen's paper [UMB, 19(2) 147-165 1993] to demonstrate that breathing the elevated carbon dioxide levels present in NASA vehicles suppresses this signal making stone imaging more difficult. We have since developed imaging countermeasures and pushing and breaking technologies that appear less dependent on cavitation than SWL.",
"date": "2017-05",
"date_type": "published",
"publisher": "Acoustical Society of America",
"id_number": "CaltechAUTHORS:20190708-164305356",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190708-164305356",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "NIH",
"grant_number": "P01DK043881"
},
{
"agency": "NIH",
"grant_number": "K01DK104854"
},
{
"agency": "NIH",
"grant_number": "R01EB007643"
},
{
"agency": "NASA",
"grant_number": "NCC 9-58"
}
]
},
"doi": "10.1121/1.4988643",
"resource_type": "conference_item",
"pub_year": "2017",
"author_list": "Bailey, Michael; Simon, Julianna C.; et el."
},
{
"id": "https://authors.library.caltech.edu/records/bdn51-6zc33",
"eprint_id": 96976,
"eprint_status": "archive",
"datestamp": "2023-08-19 01:00:12",
"lastmod": "2023-10-20 21:48:16",
"type": "conference_item",
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"creators": {
"items": [
{
"id": "Rigas-G",
"name": {
"family": "Rigas",
"given": "Georgios"
},
"orcid": "0000-0001-6692-6437"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Beyar-Michael",
"name": {
"family": "Beyar",
"given": "Michael"
}
}
]
},
"title": "Stability of wall-bounded flows using one-way spatial integration of Navier-Stokes equations",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Fluid Dynamics",
"note": "\u00a9 2017 American Institute of Aeronautics and Astronautics. \n\nPublished Online: 5 Jan 2017. \n\nG.R. and T.C. acknowledge the support of the Boeing Company through a Strategic Research and Development Relationship Agreement CT-BA-GTA-1.\n\nSubmitted - RigasColoniusBeyar2017.pdf
",
"abstract": "A method for constructing well-posed one-way equations for calculating disturbances of slowly-varying flows was recently introduced (Towne & Colonius, JCP, Vol. 300, 2015). The linearized Navier-Stokes equations are modified such that all upstream propagating modes are removed from the operator. The resulting equations, termed one-way Navier-Stokes equations, are stable and can be solved efficiently in the frequency domain as a spatial initial value problem in which initial perturbations are specified at the domain inlet and propagated downstream by spatial integration. To date, the method has been used to predict large-scale wavepacket structures and their acoustic radiation in turbulent jets. In this paper, the method is extended and applied to wall-bounded flows. Specifically, we examine the spatial stability of two- and three-dimensional boundary layers, corresponding to the Blasius and the Falkner-Skan-Cooke flows, and predict the evolution of unstable Tollmien-Schlichting waves and crossflow vortices, respectively. The method is validated against well-known results from the literature.",
"date": "2017-01-05",
"date_type": "published",
"id_number": "CaltechAUTHORS:20190709-092102122",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092102122",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Boeing Company Strategic Research and Development Relationship",
"grant_number": "CT-BA-GTA-1"
}
]
},
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{
"id": "2017-1881",
"name": "AIAA Paper"
}
]
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"pub_year": "2017",
"author_list": "Rigas, Georgios; Colonius, Tim; et el."
},
{
"id": "https://authors.library.caltech.edu/records/58rt9-3vt66",
"eprint_id": 96971,
"eprint_status": "archive",
"datestamp": "2023-08-19 01:00:07",
"lastmod": "2023-10-20 21:47:01",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Schmidt-O-T",
"name": {
"family": "Schmidt",
"given": "Oliver T."
},
"orcid": "0000-0002-7097-0235"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Br\u00e8s-G-A",
"name": {
"family": "Br\u00e8s",
"given": "Guillaume A."
},
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}
]
},
"title": "Wavepacket intermittency and its role in turbulent jet noise",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 2017 by Oliver T. Schmidt, Tim Colonius, Guillaume A. Bres. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 5 Jan 2017. \n\nThis research was supported in part by a grant from the Office of Naval Research (grant No. N00014-16-1-2445) with Dr. Knox Millsaps as program manager. Oliver Schmidt was supported by DFG grant No. SCHM 3114/1-1. The LES study was performed at Cascade Technologies, with support from NAVAIR SBIR project, under the supervision of Dr. John T. Spyropoulos. The main LES calculations were carried out on DoD HPC systems in ERDC DSRC.\n\nPublished - SchmidtColoniusBres2017.pdf
",
"abstract": "The intermittent behavior of large-scale coherent structures in turbulent jets is studied. These structures are the primary source of jet noise, and their emitted sound is in turn characterized by rapid amplitude modulations of the pressure field. These high-energy bursts are well portrayed in the frequency-time domain by means of time-local analysis techniques. Scaleograms obtained from wavelet transforms of a single-point pressure signals, for example, enable the identification of such loud events at specific locations. Our interest, however, is in the time-local behavior of the coherent structures as a whole to gain a physical understanding of jet noise generation. For that purpose, a time series of large-eddy simulation snapshots is projected onto two sets of modal basis functions that describe the large-scale structures in the frequency-domain. The first modal basis consists of frequency-domain, or spectral, POD modes that are empirically deduced from the data. The second basis is comprised of resolvent response modes that are obtained from a linear frequency-response analysis of the mean flow. The proposed method allows us to visualize the intermittent behavior of the modal solutions in the frequency-time domain in terms of magnitude contours of the projection coefficient. The results can then be interpreted in an analogous way to wavelet scaleograms. The limitations, benefits and the potential of the method to yield a low-order representation of the flow in the time domain are discussed.",
"date": "2017-01-05",
"date_type": "published",
"id_number": "CaltechAUTHORS:20190709-092100791",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092100791",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Office of Naval Research (ONR)",
"grant_number": "N00014-16-1-2445"
},
{
"agency": "Deutsche Forschungsgemeinschaft (DFG)",
"grant_number": "SCHM 3114/1-1"
},
{
"agency": "Naval Air Systems Command (NAVAIR)"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2017-0686",
"name": "AIAA Paper"
}
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"doi": "10.2514/6.2017-0686",
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"pub_year": "2017",
"author_list": "Schmidt, Oliver T.; Colonius, Tim; et el."
},
{
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"eprint_status": "archive",
"datestamp": "2023-08-22 19:08:13",
"lastmod": "2023-10-23 20:20:42",
"type": "conference_item",
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"creators": {
"items": [
{
"id": "Maeda-Kazuki",
"name": {
"family": "Maeda",
"given": "Kazuki"
},
"orcid": "0000-0002-5729-6194"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Kreider-W",
"name": {
"family": "Kreider",
"given": "Wayne"
}
},
{
"id": "Maxwell-A-D",
"name": {
"family": "Maxwell",
"given": "Adam"
}
},
{
"id": "Bailey-M-R",
"name": {
"family": "Bailey",
"given": "Michael"
}
}
]
},
"title": "Modeling and experimental analysis of acoustic cavitation bubble clouds for burst-wave lithotripsy",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Acoustic signal processing; Fluid flows; Cavitation bubbles; Acoustic field; Acoustical effects; Optical imaging; Organs; Hydrophone; Ultrasound; Medical diagnosis",
"note": "\u00a9 Acoustical Society of America. \n\nPublished Online: 18 November 2016. \n\nFunding supported by NIH 2P01-DK043881.",
"abstract": "Understanding the dynamics of cavitation bubble clouds formed inside a human body is critical for the design of burst-wave lithotripsy (BWL), a newly proposed method that uses focused ultrasound pulses with amplitude of O(10) MPa and frequency of O(0.1) MHz to fragment kidney stones. We present modeling and three-dimensional direct numerical simulations of interactions between bubble clouds and ultrasound pulses in water. We study two configurations: isolated clouds in a free field, and clouds near a rigid surface. In the modeling, we solve for the bubble radius evolution and continuous flow field using a WENO-based compressible flow solver. In the solver, Lagrangian bubbles are coupled with the continuous phase, defined on an Eulerian grid, at the sub-grid scale using volume averaging techniques. Correlations between the initial void fraction and the maximum collapse pressure in the cloud are discussed. We demonstrate acoustic imaging of the bubbles by post-processing simulated pressure signals at particular sensor locations indicating waves scattered by the clouds. Finally, we compare the simulation results with experimental results including high-speed imaging and hydrophone measurements. The time evolution of the cloud void fraction and the scattered acoustic field in the simulation agree with the experimental results.",
"date": "2016-11-18",
"date_type": "published",
"id_number": "CaltechAUTHORS:20190709-092102986",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092102986",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "NIH",
"grant_number": "2P01-DK043881"
}
]
},
"doi": "10.1121/1.4970532",
"resource_type": "conference_item",
"pub_year": "2016",
"author_list": "Maeda, Kazuki; Colonius, Tim; et el."
},
{
"id": "https://authors.library.caltech.edu/records/tt3ht-99f41",
"eprint_id": 96970,
"eprint_status": "archive",
"datestamp": "2023-08-22 19:08:10",
"lastmod": "2023-10-23 20:20:44",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Schmidt-O-T",
"name": {
"family": "Schmidt",
"given": "Oliver T."
},
"orcid": "0000-0002-7097-0235"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Br\u00e8s-G-A",
"name": {
"family": "Br\u00e8s",
"given": "Guillaume"
},
"orcid": "0000-0003-2507-8659"
}
]
},
"title": "Modeling the Generation of Supersonic Turbulent Jet Noise by Large-Scale Coherent Structures",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Fluid jets; Stochastic processes; Operator theory; Fluid dynamics; Acoustic waves; Supersonics",
"note": "\u00a9 2016 Acoustical Society of America. \n\nPublished Online: 18 November 2016.",
"abstract": "Large-scale coherent structures, or wavepackets, are a salient feature of turbulent jets, and the main source of jet mixing noise at aft angles. They are extracted from a high-fidelity Mach 1.5 LES database as spectral POD mode estimates. These most energetic wavepackets obtained via POD and their acoustic far-field radiation patterns are compared to solution to the one-way Euler (OWE) equations recently introduced by Towne & Colonius (AIAA Paper 2013-2171, 2013; AIAA Paper 2014-2903, 2014). Within the OWE framework, the linearized Euler equations are modified such that all upstream propagating acoustic wave components are removed from the solution. The resulting spatial initial value problem can be solved in a stable and computationally efficient manner by downstream marching the solution. Additionally, the scenario of stochastic forcing of wavepackets by the surrounding turbulence is considered in a resolvent analysis. The resolvent analysis allows for the computation of optimal forcing distributions and corresponding responses. It is based on a singular value decomposition of the transfer function of the governing linear operator. The results of the both methods, OWE and resolvent analysis, are compared to the most energetic POD modes with a special focus on far-field radiation patterns and computational efficiency.",
"date": "2016-11-18",
"date_type": "published",
"id_number": "CaltechAUTHORS:20190709-092100696",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092100696",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"doi": "10.1121/1.4969657",
"resource_type": "conference_item",
"pub_year": "2016",
"author_list": "Schmidt, Oliver T.; Colonius, Tim; et el."
},
{
"id": "https://authors.library.caltech.edu/records/485bj-er132",
"eprint_id": 96965,
"eprint_status": "archive",
"datestamp": "2023-09-15 06:20:03",
"lastmod": "2023-10-23 21:25:26",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Tsai-Hsieh-Chen",
"name": {
"family": "Tsai",
"given": "Hsieh-Chen"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Numerical Investigation of Self-Starting Capability of Vertical-Axis Wind Turbines at Low Reynolds Numbers",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Applied Aerodynamics",
"note": "\u00a9 2016 by Hsieh-Chen Tsai. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 10 Jun 2016. \n\nThis project is sponsored by the Caltech Field Laboratory for Optimized Wind Energy with Prof. John Dabiri as PI under the support of the Gordon and Betty Moore Foundation. We would like to thank Prof. John Dabiri and Dr. Daniel Araya for providing the experimental data and their advice on this research. We would also like to thank Prof. Beverley McKeon and Dr. Reeve Dunne for their helpful comments on our work.\n\nPublished - TsaiColonius2016a.pdf
",
"abstract": "The self-starting capability of a NACA 0018 multi-bladed vertical-axis wind turbine is numerically investigated. The immersed boundary method is used to simulate the flow around a two-dimensional cross section of the wind turbine and the predictor-corrector method is used to couple the equation of motion of the turbine. A simple load model, which is linearly proportional to turbine angular velocity, is used for the load of the turbine. The angular velocity is characterized as a function of Reynolds number, density ratio, and viscous coefficient of the proposed load model. The power outputs and moment coefficients of motor-driven and flow-driven vertical-axis wind turbine are compared. For a particular Reynolds number, as the load on the flow-driven turbine is increased, the tip speed is reduced until the turbine fails to coherently rotate. The flow-driven and motor-driven moment coefficients in the computation have good agreement between each other and are qualitatively similar to the torque measured in experiments. These computations suggest that the load of a flow-driven turbine can be well-represented by the proposed load model and a motor-driven turbine can reproduce the physics of a flow-driven turbine within the range of tip-speed ratio examined. A simple model is proposed in order to analyze the starting torque. By assuming that the inertia of the blade is much larger than the fluid, the turbine can be considered stationary in the flow. The starting torque distribution of a multi-bladed turbine indicates the important orientations corresponding to maximum torque generation, at which a self-starting turbine always starts, and a stable equilibrium, where a non-self-starting turbine oscillates. These features agree with observations from the full simulations of the starting process. We further model the starting torque distribution by considering a single blade at different orientations, and construct starting torque distributions for multi-bladed turbines by linearly combining the torques at the respective positions of the blades. We show that this approximation is valid for a sufficiently low turbine solidity of about 0.5. Using this model, we find optimal starting configuration for a multi-bladed low-solidity vertical-axis wind turbine.",
"date": "2016-06-10",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics (AIAA)",
"id_number": "CaltechAUTHORS:20190709-092100223",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092100223",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Gordon and Betty Moore Foundation"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2016-3731",
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"author_list": "Tsai, Hsieh-Chen and Colonius, Tim"
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"lastmod": "2023-10-20 21:46:35",
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"items": [
{
"id": "Cavalieri-A-V-G",
"name": {
"family": "Cavalieri",
"given": "Andr\u00e9 V. G."
},
"orcid": "0000-0003-4283-0232"
},
{
"id": "Sasaki-Kenzo",
"name": {
"family": "Sasaki",
"given": "Kenzo"
},
"orcid": "0000-0002-3347-4996"
},
{
"id": "Schmidt-O-T",
"name": {
"family": "Schmidt",
"given": "Oliver"
},
"orcid": "0000-0002-7097-0235"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Jordan-P",
"name": {
"family": "Jordan",
"given": "Peter"
},
"orcid": "0000-0001-8576-5587"
},
{
"id": "Br\u00e8s-G-A",
"name": {
"family": "Br\u00e8s",
"given": "Guillaume A."
},
"orcid": "0000-0003-2507-8659"
}
]
},
"title": "High-frequency wavepackets in turbulent jets",
"ispublished": "unpub",
"full_text_status": "public",
"note": "\u00a9 2016 by Andr\u00e9 V. G. Cavalieri. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 27 May 2016. \n\nAVGC and PJ acknowledge support from the Science Without Borders program (project number A073/2013). AVGC was supported by a CNPq research scholarship, and by CNPq grant 444796/2014-2. AT and TC gratefully acknowledge support from the Office of Naval Research under contract N0014-11-1-0753. The LES studies are supported by NAVAIR SBIR project, under the supervision of Dr. John T. Spyropoulos. The main calculations were carried out on CRAY XE6 machines at DoD supercomputer facilities in ERDC DSRC\n\nPublished - CavalieriSasakiJordanEtAl2016.pdf
",
"abstract": "Wavepackets obtained as solutions of the flow equations linearised around the mean flow have been shown in recent work to yield good agreement with the amplitudes and phases of turbulent fluctuations in jets. Compelling agreement has been demonstrated up to Strouhal numbers, St \u2248 1. We extend the range of validity of wavepacket models to higher values, 1.0 < St < 4.0, by comparing Parabolised Stability Equation solutions with well resolved large-eddy simulation data. The initial growth rates of the high-frequency fluctuations continue to be well predicted, but saturation occurs earlier and agreement with simulation begins to deteriorate upstream of the end of the potential core of the jet. Results show that near-nozzle dynamics for a broad range of frequencies can be modelled using linearised models, which capture well the spatial growth of Kelvin-Helmholtz wavepackets for all the studied Strouhal numbers.",
"date": "2016-05-27",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics (AIAA)",
"id_number": "CaltechAUTHORS:20190709-092059776",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092059776",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Science Without Borders",
"grant_number": "A073/2013"
},
{
"agency": "Conselho Nacional de Desenvolvimento Cient\u00edfico e Tecnol\u00f3gico (CNPq)",
"grant_number": "444796/2014-2"
},
{
"agency": "Office of Naval Research (ONR)",
"grant_number": "N0014-11-1-0753"
},
{
"agency": "Navy Naval Air Systems (NAVAIR)"
}
]
},
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{
"id": "2016-3056",
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"author_list": "Cavalieri, Andr\u00e9 V. G.; Sasaki, Kenzo; et el."
},
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"eprint_status": "archive",
"datestamp": "2023-08-20 11:45:50",
"lastmod": "2023-10-20 21:57:16",
"type": "conference_item",
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"creators": {
"items": [
{
"id": "Br\u00e8s-G-A",
"name": {
"family": "Br\u00e8s",
"given": "Guillaume A."
},
"orcid": "0000-0003-2507-8659"
},
{
"id": "Jaunet-V",
"name": {
"family": "Jaunet",
"given": "Vincent"
}
},
{
"id": "Le-Rallic-M",
"name": {
"family": "Le Rallic",
"given": "Maxime"
}
},
{
"id": "Jordan-P",
"name": {
"family": "Jordan",
"given": "Peter"
},
"orcid": "0000-0001-8576-5587"
},
{
"id": "Towne-A",
"name": {
"family": "Towne",
"given": "Aaron"
},
"orcid": "0000-0002-7315-5375"
},
{
"id": "Schmidt-O-T",
"name": {
"family": "Schmidt",
"given": "Oliver T."
},
"orcid": "0000-0002-7097-0235"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Cavalieri-A-V-G",
"name": {
"family": "Cavalieri",
"given": "Andr\u00e9 V. G."
},
"orcid": "0000-0003-4283-0232"
},
{
"id": "Lele-S-K",
"name": {
"family": "Lele",
"given": "Sanjiva K."
}
}
]
},
"title": "Large eddy simulation for jet noise: azimuthal decomposition and intermittency of the radiated sound",
"ispublished": "unpub",
"full_text_status": "public",
"note": "\u00a9 2016 by the authors. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 27 May 2016. \n\nThe LES studies are supported by NAVAIR SBIR project, under the supervision of Dr. John T. Spyropoulos. The main calculations were carried out on CRAY XE6 machines at DoD supercomputer facilities in ERDC DSRC. P. Jordan acknowledges the support of the French National Research Agency (ANR) through the project COOLJAZZ.\n\nPublished - BresJaunetRallicEtAl2016.pdf
",
"abstract": "To improve understanding and modeling of jet-noise source mechanisms, extensive experimental and numerical databases are generated for an isothermal Mach 0.9 turbulent jet at Reynolds number Re = 10^6. The large eddy simulations (LES) feature localized adaptive mesh refinement, synthetic turbulence and wall modeling inside the nozzle to match the fully turbulent nozzle-exit boundary layers in the experiments. Long LES databases are collected for two grids with different mesh resolutions in the jet plume. Comparisons with the experimental measurements show good agreement for the flow and sound predictions, with the far-field noise spectra matching microphone data to within 0.5 dB for most relevant angles and frequencies. Preliminary results on the radiated noise azimuthal decomposition and temporal intermittency are also discussed. The azimuthal analysis shows that the axisymmetric mode is dominant at the peak radiation angles and that the first 3 Fourier azimuthal modes of the LES data recover more than 97% of the total acoustic energy at these angles. The temporal analysis highlights the presence of recurring intermittency in the radiated sound for the low-frequency range and main downstream angles. At these frequencies and angles, temporally-localized bursts of noise can reach levels up to 3 or 4 dB higher (or lower) than the long-time average.",
"date": "2016-05-27",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics (AIAA)",
"id_number": "CaltechAUTHORS:20190712-112321549",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190712-112321549",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Naval Air Systems Command (NAVAIR)"
},
{
"agency": "Agence Nationale pour la Recherche (ANR)",
"grant_number": "COOLJAZZ"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2016-3050",
"name": "AIAA Paper"
}
]
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"doi": "10.2514/6.2016-3050",
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"pub_year": "2016",
"author_list": "Br\u00e8s, Guillaume A.; Jaunet, Vincent; et el."
},
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"eprint_id": 96969,
"eprint_status": "archive",
"datestamp": "2023-08-20 11:45:45",
"lastmod": "2023-10-20 21:46:57",
"type": "conference_item",
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"creators": {
"items": [
{
"id": "Schmidt-O-T",
"name": {
"family": "Schmidt",
"given": "Oliver T."
},
"orcid": "0000-0002-7097-0235"
},
{
"id": "Towne-A",
"name": {
"family": "Towne",
"given": "Aaron"
},
"orcid": "0000-0002-7315-5375"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Jordan-P",
"name": {
"family": "Jordan",
"given": "Peter"
},
"orcid": "0000-0001-8576-5587"
},
{
"id": "Jaunet-V",
"name": {
"family": "Jaunet",
"given": "Vincent"
}
},
{
"id": "Cavalieri-A-V-G",
"name": {
"family": "Cavalieri",
"given": "Andr\u00e9 V. G."
},
"orcid": "0000-0003-4283-0232"
},
{
"id": "Br\u00e8s-G-A",
"name": {
"family": "Br\u00e8s",
"given": "Guillaume A."
},
"orcid": "0000-0003-2507-8659"
}
]
},
"title": "Super- and multi-directive acoustic radiation by linear global modes of a turbulent jet",
"ispublished": "unpub",
"full_text_status": "public",
"note": "\u00a9 2016 by Oliver T. Schmidt. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 27 May 2016. \n\nOTS gratefully acknowledges support by DFG grant no. 3114/1-1. AT and TC gratefully acknowledge support from the Office of Naval Research under contract N0014-11-1-0753. AVGC and PJ acknowledge support from the Science Without Borders program (project number A073/2013). The LES study was supported by NAVAIR SBIR project, under the supervision of Dr. John T. Spyropoulos. The main LES calculations were carried out on CRAY XE6 machines at DoD HPC facilities in ERDC DSRC.\n\nPublished - SchmidtTowneColoniusEtAl2016.pdf
",
"abstract": "The mean flow stability of a Mach 0.9 turbulent jet is investigated by means of global linear theory with a focus on acoustic effects. A novel class of resonant acoustic modes that are trapped within the potential core, and whose eigenvalues appear as discrete branches in the global stability spectrum, is studied in detail. A dispersion relation is reconstructed from the global modes, and shown to accurately predict energy bands observed in the PSD of a high-fidelity LES. Similarly, the acoustic far-field radiation patterns of the trapped modes are compared to the LES. A favorable agreement between the global mode waveforms and coherent structures educed from the LES is found for both the trapped acoustic wave component inside the core and the far-field radiation.",
"date": "2016-05-27",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics (AIAA)",
"id_number": "CaltechAUTHORS:20190709-092100617",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092100617",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Deutsche Forschungsgemeinschaft (DFG)",
"grant_number": "3114/1-1"
},
{
"agency": "Office of Naval Research (ONR)",
"grant_number": "N0014-11-1-0753"
},
{
"agency": "Science Without Borders",
"grant_number": "A073/2013"
},
{
"agency": "Naval Air Systems Command (NAVAIR)"
}
]
},
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{
"id": "2016-2808",
"name": "AIAA Paper"
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"doi": "10.2514/6.2016-2808",
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"author_list": "Schmidt, Oliver T.; Towne, Aaron; et el."
},
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"id": "https://authors.library.caltech.edu/records/e3rqf-bjg58",
"eprint_id": 96952,
"eprint_status": "archive",
"datestamp": "2023-08-20 11:45:30",
"lastmod": "2023-10-20 21:38:51",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Jaunet-V",
"name": {
"family": "Jaunet",
"given": "Vincent"
}
},
{
"id": "Jordan-P",
"name": {
"family": "Jordan",
"given": "Peter"
},
"orcid": "0000-0001-8576-5587"
},
{
"id": "Cavalieri-A-V-G",
"name": {
"family": "Cavalieri",
"given": "Andr\u00e9 V."
},
"orcid": "0000-0003-4283-0232"
},
{
"id": "Towne-A",
"name": {
"family": "Towne",
"given": "Aaron"
},
"orcid": "0000-0002-7315-5375"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Schmidt-O-T",
"name": {
"family": "Schmidt",
"given": "Oliver"
},
"orcid": "0000-0002-7097-0235"
},
{
"id": "Br\u00e8s-G-A",
"name": {
"family": "Br\u00e8s",
"given": "Guillaume A."
},
"orcid": "0000-0003-2507-8659"
}
]
},
"title": "Tonal dynamics and sound in subsonic turbulent jets",
"ispublished": "unpub",
"full_text_status": "public",
"note": "\u00a9 2016 by P. Jordan, CNRS. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 27 May 2016.\n\nPublished - JaunetJordanCavalieriEtAl2016.pdf
",
"abstract": "Acoustic waves trapped in the potential core of subsonic turbulent jets have recently been observed and explained by Towne et al. We show that these waves also radiate outside the jet, primarily into the upstream arc. We provide an experimental identification of the Mach-number dependence of the phenomenon, which indicates that the modes are active even when evanescent, probably due to turbulent forcing. Finally, we show that for Mach numbers lower than about 0.8, the strong tonal dynamics and sound radiation (up to 170dB) that occur when a sharp edge is placed close to the jet are related to a resonance mechanism involving convective hydrodynamic wavepackets and a 'slow', upstreampropagating, trapped acoustic mode. A Helmholtz scaling of the resonance at higher Mach number suggests involvement of the 'fast' trapped modes in the range 0.8 \u2264 M \u2264 1.",
"date": "2016-05-27",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics (AIAA)",
"id_number": "CaltechAUTHORS:20190709-092059115",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092059115",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"other_numbering_system": {
"items": [
{
"id": "2016-3016",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2016-3016",
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},
"resource_type": "conference_item",
"pub_year": "2016",
"author_list": "Jaunet, Vincent; Jordan, Peter; et el."
},
{
"id": "https://authors.library.caltech.edu/records/jc7tm-gme66",
"eprint_id": 96966,
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"datestamp": "2023-08-20 11:45:39",
"lastmod": "2023-10-20 21:46:49",
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"creators": {
"items": [
{
"id": "Towne-A",
"name": {
"family": "Towne",
"given": "Aaron"
},
"orcid": "0000-0002-7315-5375"
},
{
"id": "Cavalieri-A-V-G",
"name": {
"family": "Cavalieri",
"given": "Andr\u00e9 V. G."
},
"orcid": "0000-0003-4283-0232"
},
{
"id": "Jordan-P",
"name": {
"family": "Jordan",
"given": "Peter"
},
"orcid": "0000-0001-8576-5587"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Jaunet-V",
"name": {
"family": "Jaunet",
"given": "Vincent"
}
},
{
"id": "Schmidt-O-T",
"name": {
"family": "Schmidt",
"given": "Oliver T."
},
"orcid": "0000-0002-7097-0235"
},
{
"id": "Br\u00e8s-G-A",
"name": {
"family": "Br\u00e8s",
"given": "Guillaume A."
},
"orcid": "0000-0003-2507-8659"
}
]
},
"title": "Trapped acoustic waves in the potential core of subsonic jets",
"ispublished": "unpub",
"full_text_status": "public",
"note": "\u00a9 2016 by Aaron Towne, Andr\u00e9 V. G. Cavalieri, Peter Jordan, Tim Colonius, Vincent Jaunet, Oliver T. Schmidt, and Guillaume A. Br\u00e8s. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 27 May 2016. \n\nAT and TC gratefully acknowledge support from the Office of Naval Research under contract N0014-11-1-0753. AVGC and PJ acknowledge support from the Science Without Borders program (project number A073/2013). OTS was supported by DFG grant no. 3114/1-1. The LES study was supported by NAVAIR SBIR project, under the supervision of Dr. John T. Spyropoulos. The main LES calculations were carried out on CRAY XE6 machines at DoD HPC facilities in ERDC DSRC.\n\nPublished - TowneCavalieriJordanEtAl2016.pdf
",
"abstract": "The purpose of this paper is to characterize and model waves that are observed within the potential core of subsonic jets and that have been previously detected as tones in the near-nozzle region. Using three models (the linearized Euler equations, a cylindrical vortex sheet, and a cylindrical duct with pressure release boundary conditions), we show that these waves can be described by linear modes of the jet and correspond to acoustic waves that are trapped within the potential core. At certain frequencies, these trapped waves resonate due to repeated reflection between end conditions provided by the nozzle and the streamwise contraction of the potential core. Our models accurately capture numerous aspects the potential core waves that are extracted from large-eddy-simulation data of a Mach 0.9 isothermal jet. Furthermore, the vortex sheet model indicates that this behavior is possible for only a limited range of Mach numbers that is consistent with previous experimental observations.",
"date": "2016-05-27",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics (AIAA)",
"id_number": "CaltechAUTHORS:20190709-092100372",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092100372",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Office of Naval Research (ONR)",
"grant_number": "N0014-11-1-0753"
},
{
"agency": "Science Without Borders",
"grant_number": "A073/2013"
},
{
"agency": "Deutsche Forschungsgemeinschaft (DFG)",
"grant_number": "3114/1-1"
},
{
"agency": "Naval Air Systems Command (NAVAIR)"
}
]
},
"other_numbering_system": {
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{
"id": "2016-2809",
"name": "AIAA Paper"
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]
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"doi": "10.2514/6.2016-2809",
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},
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"author_list": "Towne, Aaron; Cavalieri, Andr\u00e9 V. G.; et el."
},
{
"id": "https://authors.library.caltech.edu/records/zbn65-cqg97",
"eprint_id": 96956,
"eprint_status": "archive",
"datestamp": "2023-08-20 09:51:10",
"lastmod": "2023-10-20 21:46:24",
"type": "conference_item",
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"creators": {
"items": [
{
"id": "Darakananda-D",
"name": {
"family": "Darakananda",
"given": "Darwin"
}
},
{
"id": "Eldredge-J-D",
"name": {
"family": "Eldredge",
"given": "Jeff D."
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Williams-D-R",
"name": {
"family": "Williams",
"given": "David R."
}
}
]
},
"title": "A Vortex Sheet/Point Vortex Dynamical Model For Unsteady Separated Flows",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Fluid Dynamics",
"note": "\u00a9 2015 by the authors. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 2 Jan 2016. \n\nSupport by the U.S. Air Force Office of Scientific Research (FA9550-14-1-0328) with program manager Dr. Douglas Smith is gratefully acknowledged.\n\nPublished - DarakanandaEldredgeColoniusEtAl2016.pdf
",
"abstract": "This paper presents a hybrid vortex sheet/point vortex method for modeling unsteady separated flows. We use vortex sheets to capture the dynamics of the shear layers immediately behind a wing in motion. The sheets provide a natural way of capturing vortex shedding, a feature missing from many point vortex models. We overcome the high computational cost traditionally associated with vortex sheet methods by approximating the spiraling cores of the sheets using point vortices with time-varying circulation. Circulation is continuously truncated from the tips of the vortex sheets and fed into their associated point vortices. To compensate for the discontinuous force response that results from this redistribution of vorticity, we adjust the velocity of the variable strength point vortices. We demonstrate the viability of the method by modeling the impulsive translation of a wing at a fixed angle of attack. We show that the proposed model correctly predicts the dynamics of large-scale vortical structures in the flow by comparing the distribution of vorticity from results of high-fidelity simulation, a model using only vortex sheets, and the proposed model. For the test cases attempted, the hybrid model predicts similar force responses to those of the sheet-only model, while being orders of magnitude faster.",
"date": "2016-01-02",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics (AIAA)",
"id_number": "CaltechAUTHORS:20190709-092059444",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092059444",
"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": "FA9550-14-1-0328"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2016-2072",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2016-2072",
"primary_object": {
"basename": "DarakanandaEldredgeColoniusEtAl2016.pdf",
"url": "https://authors.library.caltech.edu/records/zbn65-cqg97/files/DarakanandaEldredgeColoniusEtAl2016.pdf"
},
"resource_type": "conference_item",
"pub_year": "2016",
"author_list": "Darakananda, Darwin; Eldredge, Jeff D.; et el."
},
{
"id": "https://authors.library.caltech.edu/records/tk21n-wap73",
"eprint_id": 97095,
"eprint_status": "archive",
"datestamp": "2023-08-20 09:51:14",
"lastmod": "2023-10-20 21:56:26",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "An-Xuanhong",
"name": {
"family": "An",
"given": "Xuanhong"
}
},
{
"id": "Williams-D-R",
"name": {
"family": "Williams",
"given": "David R."
}
},
{
"id": "Eldredge-J-D",
"name": {
"family": "Eldredge",
"given": "Jeff"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Modeling Dynamic Lift Response to Actuation",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Fluid Dynamics",
"note": "\u00a9 2016 American Institute of Aeronautics and Astronautics. \n\nPublished Online: 2 Jan 2016. \n\nSupport by the U.S. Air Force Office of Scientific Research (FA9550-14-1-0328) with program manager Dr. Douglas Smith is gratefully acknowledged.\n\nSubmitted - AnWilliamsEldredgeEtAl2016.pdf
",
"abstract": "The dynamic lift response of an airfoil to sinusoidal amplitude variations from a synthetic jet actuator was studied. The wing was at a fixed angle of attack, and the actuator operated in a 'burst-mode' with a fixed duty cycle. The actuator burst mplitude was used as a control signal, which was varied between an 'off ' condition and the actuator saturation voltage. Three dimensionless frequencies were examined, corresponding to k = [(\u03c0fc)/(U\u221e)] = 0.064, 0.128, and 0.25. Hysteresis loops in the lift increment were observed, whose shapes were dependent on the control frequency. Three different approaches to modeling the lift increment response were explored: a linear convolution approach, a nonlinear time delay and decay model, and a combination of those two. The linear convolution captures the high frequency content of the lift response, but becomes inaccurate when the actuator burst period is less than 3.5 convective times. The time delay and decay model reproduces the low frequency component of the lift response, but not the high frequency. When the control frequency becomes large, (k = 0.25), then the largest time-varying lift increment is produced near the minimum of the actuator voltage.",
"date": "2016-01-02",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics (AIAA)",
"id_number": "CaltechAUTHORS:20190712-112320249",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190712-112320249",
"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": "FA9550-14-1-0328"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2016-0058",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2016-0058",
"primary_object": {
"basename": "AnWilliamsEldredgeEtAl2016.pdf",
"url": "https://authors.library.caltech.edu/records/tk21n-wap73/files/AnWilliamsEldredgeEtAl2016.pdf"
},
"resource_type": "conference_item",
"pub_year": "2016",
"author_list": "An, Xuanhong; Williams, David R.; et el."
},
{
"id": "https://authors.library.caltech.edu/records/b5g4h-7dg30",
"eprint_id": 97111,
"eprint_status": "archive",
"datestamp": "2023-08-20 06:57:13",
"lastmod": "2023-10-20 21:57:20",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Br\u00e8s-G-A",
"name": {
"family": "Br\u00e8s",
"given": "Guillaume A."
},
"orcid": "0000-0003-2507-8659"
},
{
"id": "Jaunet-V",
"name": {
"family": "Jaunet",
"given": "Vincent"
}
},
{
"id": "Le-Rallic-M",
"name": {
"family": "Le Rallic",
"given": "Maxime"
}
},
{
"id": "Jordan-P",
"name": {
"family": "Jordan",
"given": "Peter"
},
"orcid": "0000-0001-8576-5587"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Lele-S-K",
"name": {
"family": "Lele",
"given": "Sanjiva K."
}
}
]
},
"title": "Large eddy simulation for jet noise: the importance of getting the boundary layer right",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 2015 by the authors. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 18 Jun 2015. \n\nThe preliminary LES studies were supported by NAVAIR SBIR project, under the supervision of Dr. John T. Spyropoulos. The main calculations were carried out on CRAY XE6 machines at DoD supercomputer facilities in ERDC DSRC. P. Jordan acknowledges the support of the French National Research Agency (ANR) through the project COOLJAZZ. Part of this work was performed during the Center for Turbulence Research Summer Program 2014 at Stanford University.\n\nPublished - BresJaunetLeRallicEtAl2015.pdf
",
"abstract": "Large eddy simulations of an isothermal Mach 0.9 jet issued from a convergent-straight nozzle are performed at Reynolds number 1 \u00d7 10^6. The flow configuration and operating conditions match the companion experiment conducted at the PPRIME Institute, Poitiers. To replicate the effects of the boundary layer trip present in the experiment and to ensure a turbulent jet, localized adaptive mesh refinement, synthetic turbulence, and wall modeling are used inside the nozzle. This leads to fully turbulent nozzle-exit boundary layers and results in significant improvements for the flow field and sound predictions, compared to those obtained from the typical approach based on laminar flow assumption in the nozzle. The far-field noise spectra now match the experimental measurements to within 0.5 dB for relevant angles and frequencies. As a next step toward better understanding of turbulent jet noise, the large database collected during the simulation is currently being used for reduced order modeling and wavepacket analysis.",
"date": "2015-06-18",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190712-112322014",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190712-112322014",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Naval Air Systems Command (NAVAIR)"
},
{
"agency": "Agence Nationale pour la Recherche (ANR)",
"grant_number": "COOLJAZZ"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2015-2535",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2015-2535",
"primary_object": {
"basename": "BresJaunetLeRallicEtAl2015.pdf",
"url": "https://authors.library.caltech.edu/records/b5g4h-7dg30/files/BresJaunetLeRallicEtAl2015.pdf"
},
"resource_type": "conference_item",
"pub_year": "2015",
"author_list": "Br\u00e8s, Guillaume A.; Jaunet, Vincent; et el."
},
{
"id": "https://authors.library.caltech.edu/records/0kwpw-jvy14",
"eprint_id": 97121,
"eprint_status": "archive",
"datestamp": "2023-08-20 06:57:30",
"lastmod": "2023-10-20 21:57:59",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Sinha-A",
"name": {
"family": "Sinha",
"given": "Aniruddha"
},
"orcid": "0000-0002-7122-3549"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Linear Stability Implications of Mean Flow Variations in Turbulent Jets Issuing from Serrated Nozzles",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 2015 by Aniruddha Sinha and Tim Colonius. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 18 Jun 2015. \n\nAS acknowledges support from Industrial Research and Consultancy Center of Indian Institute of Technology Bombay, via the seed grant program. The authors benefited from interactions with Andr\u00e9 Cavalieri, Francisco Laj\u00fas Jr. and Peter Jordan.\n\nPublished - SinhaColonius2015.pdf
",
"abstract": "Nozzle serrations or chevrons are being deployed for reducing the noise from jet engines. The turbulent mean flow field of such jets takes on a serrated character, and the linear stability eigenspectrum for such serrated mean flows determines the evolution of the coherent wavepackets that are linked to the aft angle noise radiated. In particular, the lower the growth rate and phase speed of the instability, the lower is the expected noise radiation. Here we identify four parameters of the mean flow serrations \u2013 viz. number of lobes, their protrusion, their width relative of overall circumference, and the average thickness of the shear layer. These four parameters are systematically varied to synthesize a family of mean flow profiles. The corresponding stability analyses indicate the following trends. As expected from results for round jets, the average shear layer thickness has an inverse effect on both growth rate and phase speed. Deeper penetration and higher number of lobes reduce the growth rate of the relevant instability while mildly enhancing its phase speed. The relative width of the lobes do not appear to be a relevant parameter. These theoretical trends are supported by noise measurements in the parametric study on chevron nozzles performed at NASA.",
"date": "2015-06-18",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190712-112322917",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190712-112322917",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Indian Institute of Technology Bombay"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2015-3125",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2015-3125",
"primary_object": {
"basename": "SinhaColonius2015.pdf",
"url": "https://authors.library.caltech.edu/records/0kwpw-jvy14/files/SinhaColonius2015.pdf"
},
"resource_type": "conference_item",
"pub_year": "2015",
"author_list": "Sinha, Aniruddha and Colonius, Tim"
},
{
"id": "https://authors.library.caltech.edu/records/8r1qg-kbh77",
"eprint_id": 97118,
"eprint_status": "archive",
"datestamp": "2023-08-20 06:57:25",
"lastmod": "2023-10-20 21:57:44",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Tissot-Gilles",
"name": {
"family": "Tissot",
"given": "Gilles"
}
},
{
"id": "Zhang-Mengqi",
"name": {
"family": "Zhang",
"given": "Mengqi"
}
},
{
"id": "Laj\u00fas-Francisco-C-Jr",
"name": {
"family": "Laj\u00fas",
"given": "Francisco C., Jr."
}
},
{
"id": "Cavalieri-A-V-G",
"name": {
"family": "Cavalieri",
"given": "Andr\u00e9 V. G."
},
"orcid": "0000-0003-4283-0232"
},
{
"id": "Jordan-P",
"name": {
"family": "Jordan",
"given": "Peter"
},
"orcid": "0000-0001-8576-5587"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Sensitivity of wavepackets in jets to non-linear effects: the role of the critical layer",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 2012 by the authors. Published by the American Institute of Aeronautics and Astronautics, Inc. with permission. \n\nPublished Online: 18 Jun 2015. \n\nThis work was supported by the program Science Without Borders (project A073/2013), the ANR project COOLJAZZ and through fundings from the Fondation Universit\u00e9 de Poitiers.\n\nSubmitted - TissotZhangLajusEtAl2015.pdf
",
"abstract": "Linear instability waves, wavepackets, are key building blocks for the jet-noise problem. It has been shown in previous work that linear models correctly predict the evolution of axisymmetric wavepackets up to the end of the potential core. Beyond this station linear models fail to predict single-point statistics; they fail more broadly in the prediction of two-point properties such as coherence; and their underprediction of the radiated noise is believed to be associated with these errors. Non-linearity is the likely missing piece. But how might it be incorporated? What are the essential underlying mechanisms? Might it be amenable to a reduced-order modelling methodology? The work described in this paper is concerned with these questions. The non-linear interactions are considered as an \"external\" harmonic forcing of the standard linear model; the forcing can be viewed as comprising those Fourier components of the non-linear term of the Navier-Stokes equations which are most amplified by the linear wavepackets. \n\nThis modelling framework is explored using three complementary problems in which we try to understand the relationship between \"external\" forcing, linear system and flow response. The response of an incompressible, two-dimensional, locally parallel, shear-flow to direct, spatially localised, harmonic forcing is first considered. A resolvant analysis is then performed, again in a locally parallel context, both for the incompressible, 2D problem and for a compressible axisymmetric shear-flow where the mean flow is taken from experiments. Finally, in order to incorporate the slow axial variation of the real jet, a novel approach is considered where 4D-Var data assimilation is applied using experimental data and the Parabolised Stability Equations (PSE-4D-Var). The objective of this third, data-driven, approach is to search for an optimal forcing that might improve the match between wavepaket solutions and measurements. \n\nIn all of the problems considered the critical layer, where the phase speed of the wave is equal to the local mean velocity, is found to be relevant. It is at this point that the sensitivity of the linear waves to non-linearity is greatest. In the 2D, incompressible, problem the largest response is produced when the flow is forced in the vicinity of the critical layer. The resolvant analyses show optimal forcing modes that peak on the critical layer and the optimal response modes have a critical-layer structure. The PSE-4D-Var approach shows highest sensitivity near the critical layer. Furthermore, the structure of the forced perturbations are tilted in a manner that suggests an Orr-like mechanism.\n\nThe ensemble of results suggest that the critical layer may play a central role in the modelling of wavepackets in subsonic turbulent jets, and indeed may be the key to remedying the deficiencies evoked above.",
"date": "2015-06-18",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190712-112322634",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190712-112322634",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Science Without Borders",
"grant_number": "A073/2013"
},
{
"agency": "Agence Nationale pour la Recherche (ANR)",
"grant_number": "COOLJAZZ"
},
{
"agency": "Fondation Universit\u00e9 Poitiers"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2015-2218",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2015-2218",
"primary_object": {
"basename": "TissotZhangLajusEtAl2015.pdf",
"url": "https://authors.library.caltech.edu/records/8r1qg-kbh77/files/TissotZhangLajusEtAl2015.pdf"
},
"resource_type": "conference_item",
"pub_year": "2015",
"author_list": "Tissot, Gilles; Zhang, Mengqi; et el."
},
{
"id": "https://authors.library.caltech.edu/records/nc2tg-bc569",
"eprint_id": 97113,
"eprint_status": "archive",
"datestamp": "2023-08-20 06:57:20",
"lastmod": "2023-10-20 21:57:27",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Towne-A",
"name": {
"family": "Towne",
"given": "Aaron"
},
"orcid": "0000-0002-7315-5375"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Jordan-P",
"name": {
"family": "Jordan",
"given": "Peter"
},
"orcid": "0000-0001-8576-5587"
},
{
"id": "Cavalieri-A-V-G",
"name": {
"family": "Cavalieri",
"given": "Andr\u00e9"
},
"orcid": "0000-0003-4283-0232"
},
{
"id": "Br\u00e8s-G-A",
"name": {
"family": "Br\u00e8s",
"given": "Guillaume A."
},
"orcid": "0000-0003-2507-8659"
}
]
},
"title": "Stochastic and nonlinear forcing of wavepackets in a Mach 0.9 jet",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 2015 American Institute of Aeronautics and Astronautics. \n\nPublished Online: 18 Jun 2015. \n\nWe are grateful for support from the Center for Turbulence Research at Stanford University where a preliminary version of this analysis was performed during the 2014 Summer Program. TC and AT acknowledge earlier support of our jet noise work by the Office of Naval Research under contract N0014-11-1-0753. We would also like to thank Profs. Sanjiva Lele and Joseph Nichols for helpful discussions on this research.\n\nSubmitted - TowneColoniusJordanEtAl2015.pdf
Erratum - TowneColoniusJordanEtAl2015-correction.pdf
",
"abstract": "Recent studies have shown that while linear wavepacket models accurately reproduce experimentally observed, low azimuthal-wavenumber pressure fluctuations in the near field of turbulent jets, they significantly under-predict the intensity of the acoustic radiation produced in the subsonic case. In a linear context, \"jittering\" of the wavepackets, which can arise due to both stochastic and nonlinear interactions that force the wavepackets, has been hypothesized as a mechanism by which the radiation efficiency of wavepackets is greatly increased. We use data from a carefully validated large-eddy-simulation of a Mach 0.9 turbulent jet to explore this hypothesis. We analyze the LES data in frequency space using windowed segments of a set of snapshots spanning two thousand acoustic time units. We apply the linearized Navier-Stokes operator to this data in order to compute the non-linear forcing field that occurred in the LES simulations, and propose several techniques for educing the relation between the forcing and the observed flow fields. In particular, we employ empirical techniques to identify high energy modes (via proper orthogonal decomposition) in both the flow and acoustic fields, as well as a set of empirical resolvent modes that maximize either the gain between the forcing and flow fields, or the gain between the forcing and acoustic fields. The high gain modes are similar to the high energy modes in both cases, suggesting that the forcing fields are nearly uncorrelated in each realization. Both flow and acoustic fields appear to be driven by largely incoherent forcing corresponding to turbulence in the region of strong shear and, in particular, close to the critical layer. With the caveat that we have thus far only analyzed the axisymmetric mode of the disturbance fields, the results suggest that accurate linear wavepacket models that capture both the coherent flow and acoustic fields can be constructed if appropriate parameterizations of the stochastic forcing can be found, i.e. such forcings will excite the high gain modes to produce the observed coherent structures in both the near and far field.",
"date": "2015-06-18",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190712-112322227",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190712-112322227",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Office of Naval Research (ONR)",
"grant_number": "N0014-11-1-0753"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2015-2217",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2015-2217",
"primary_object": {
"basename": "TowneColoniusJordanEtAl2015-correction.pdf",
"url": "https://authors.library.caltech.edu/records/nc2tg-bc569/files/TowneColoniusJordanEtAl2015-correction.pdf"
},
"related_objects": [
{
"basename": "TowneColoniusJordanEtAl2015.pdf",
"url": "https://authors.library.caltech.edu/records/nc2tg-bc569/files/TowneColoniusJordanEtAl2015.pdf"
}
],
"resource_type": "conference_item",
"pub_year": "2015",
"author_list": "Towne, Aaron; Colonius, Tim; et el."
},
{
"id": "https://authors.library.caltech.edu/records/52fdt-nh656",
"eprint_id": 97117,
"eprint_status": "archive",
"datestamp": "2023-08-22 14:00:04",
"lastmod": "2023-10-23 19:09:54",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Towne-A",
"name": {
"family": "Towne",
"given": "Aaron"
},
"orcid": "0000-0002-7315-5375"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Efficient jet noise models using the one-way Euler equations",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Fluid jets; Auditory system; Fluid dynamics; Acoustic phenomena; Acoustic noise; Supersonic jets; Acoustics; Turbulence simulations; Sound generation; Acoustic field",
"note": "\u00a9 2014 Acoustical Society of America. \n\nPublished Online: 23 October 2014.",
"abstract": "Experimental and numerical investigations have correlated large-scale coherent structures in turbulent jets with acoustic radiation to downstream angles, where sound is most intense. These structures can be modeled as linear instability modes of the turbulent mean flow. The parabolized stability equations have been successfully used to estimate the near-field evolution of these modes, but are unable to properly capture the acoustic field. We have recently developed an efficient method for calculating these linear modes that properly captures the acoustic field. The linearized Euler equations are modified such that all upstream propagating acoustic modes are removed from the operator. The resulting equations, called one-way Euler equations, can be stably and efficiently solved in the frequency domain as a spatial initial value problem in which initial perturbations are specified at the flow inlet and propagated downstream by integrating the equations. We demonstrate the accuracy and efficiency of the method by using it to model sound generation and propagation in jets. The results are compared to accurate large-eddy-simulation data for both subsonic and supersonic jets.",
"date": "2014-10-23",
"date_type": "published",
"id_number": "CaltechAUTHORS:20190712-112322554",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190712-112322554",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"doi": "10.1121/1.4899470",
"resource_type": "conference_item",
"pub_year": "2014",
"author_list": "Towne, Aaron and Colonius, Tim"
},
{
"id": "https://authors.library.caltech.edu/records/fzs7a-c7b95",
"eprint_id": 97103,
"eprint_status": "archive",
"datestamp": "2023-08-22 14:00:00",
"lastmod": "2023-10-23 19:11:06",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Coralic-V",
"name": {
"family": "Coralic",
"given": "Vedran"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Modeling vascular injury due to shock-induced bubble collapse in lithotripsy",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Diseases and conditions; Fluid dynamics; Shock waves; Bubble dynamics; Viscoelastic effect; Medical diagnosis",
"note": "\u00a9 2014 Acoustical Society of America. \n\nPublished Online: 23 October 2014.",
"abstract": "Shock-induced collapse (SIC) of preexisting bubbles is investigated as a potential mechanism for vascular injury in shockwave lithotripsy (SWL). Preexisting bubbles exist under normal physiological conditions and grow larger and more numerous with ongoing treatment. We compute the three-dimensional SIC of a bubble using the multi-component Euler equations, and determine the resulting three-dimensional finite-strain deformation field in the material surrounding the collapsing bubble. We propose a criterion for vessel rupture and estimate the minimum bubble size, across clinical SWL pressures, which could result in rupture of microvasculature. Post-processing of the results and comparison to viscoelastic models for spherical bubble dynamics demonstrate that our results are insensitive to a wide range of estimated viscoelastic tissue properties during the collapse phase. During the jetting phase, however, viscoelastic effects are non-negligible. The minimum bubble size required to rupture a vessel is then estimated by adapting a previous model for the jet's penetration depth as a function of tissue viscosity.",
"date": "2014-10-23",
"date_type": "published",
"id_number": "CaltechAUTHORS:20190712-112321008",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190712-112321008",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"doi": "10.1121/1.4899946",
"resource_type": "conference_item",
"pub_year": "2014",
"author_list": "Coralic, Vedran and Colonius, Tim"
},
{
"id": "https://authors.library.caltech.edu/records/nb9qk-zbh59",
"eprint_id": 97102,
"eprint_status": "archive",
"datestamp": "2023-08-22 13:56:43",
"lastmod": "2023-10-23 19:11:57",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Towne-A",
"name": {
"family": "Towne",
"given": "Aaron"
},
"orcid": "0000-0002-7315-5375"
},
{
"id": "Schlinker-R-H",
"name": {
"family": "Schlinker",
"given": "Robert H."
}
},
{
"id": "Reba-R-A",
"name": {
"family": "Reba",
"given": "Ramons A."
}
},
{
"id": "Shannon-D-W",
"name": {
"family": "Shannon",
"given": "Dan"
}
}
]
},
"title": "Active control of noise from hot, supersonic turbulent jets",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Supersonics; Spin valves; Fluid jets; Signal processing; Microphone array; Flow boundary effects; Aircraft",
"note": "\u00a9 2014 Society of America.\n\nPublished Online: 23 October 2014.",
"abstract": "We report on an experimental and reduced-order modeling study aimed at reducing mixing noise in hot supersonic jets relevant to military aircraft. A spinning valve is used to modulate four injection nozzles near the main jet nozzle lip over a range of frequencies and mass flow rates. Diagnostics include near-, mid-, and far-field microphone arrays aimed at measuring the effect of actuation on the near-field turbulent wavepacket structures and their correlation with mixing noise. The actuators provide more than 4 dB noise reduction at peak frequencies in the aft arc, and up to 2 dB reduction in OASPL. Experiments are performed to contrast the performance of steady and unsteady blowing with different amplitudes. The results to date suggest that the noise reduction is primarily associated with attenuated wave packet activity associated with the rapidly thickened shear layers that occur with both steady and unsteady blowing. Mean flow surveys are also preformed and serve as inputs to reduced-order models for the wave packets based on parabolized stability equations. These models are in turn used to corroborate the experimental evidence suggesting mechanisms of noise suppression in the actuated flow.",
"date": "2014-10-14",
"date_type": "published",
"id_number": "CaltechAUTHORS:20190712-112320906",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190712-112320906",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"doi": "10.1121/1.4899469",
"resource_type": "conference_item",
"pub_year": "2014",
"author_list": "Colonius, Tim; Towne, Aaron; et el."
},
{
"id": "https://authors.library.caltech.edu/records/p0qx6-atn77",
"eprint_id": 97115,
"eprint_status": "archive",
"datestamp": "2023-08-20 01:25:40",
"lastmod": "2023-10-20 21:57:35",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Towne-A",
"name": {
"family": "Towne",
"given": "Aaron"
},
"orcid": "0000-0002-7315-5375"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Continued development of the one-way Euler equations: application to jets",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Environmental Impact of Aerospace Systems",
"note": "\u00a9 2014 American Institute of Aeronautics and Astronautics. \n\nPublished Online: 13 Jun 2014. \n\nThe authors gratefully acknowledge support from the Office of Naval Research under contract N0014-11-1-0753 with Dr. Brenda Henderson as technical monitor. Additionally, the authors would like to thank Professor Thomas Hagstrom, Southern Methodist University for helpful input on this work.\n\nSubmitted - TowneColonius2014.pdf
",
"abstract": "An efficient method for calculating linearized disturbances to shear flows that accurately captures their acoustic radiation was recently introduced (Towne & Colonius, AIAA Paper 2013-2171, 2013). The linearized Euler equations are modified such that all upstream propagating acoustic modes are removed from the operator. The resulting equations, called one-way Euler equations, can be stably and efficiently solved in the frequency domain as a spatial initial value problem in which initial perturbations are specified at the flow inlet and propagated downstream by integration of the equations. In this paper, we continue the development of this method with the aim of using it to model wavepackets and their acoustic radiation in turbulent jets. Before turning attention to jets, two dimensional mixing layer noise results computed using the one-way Euler equations are shown to be in excellent agreement with a direct solution of the full Euler equations. The one-way Euler operator is then shown to accurately represent all downstream modes that exist in supersonic and subsonic parallel jets, while properly eliminating the upstream acoustic modes. Finally, the method is applied to a turbulent Mach 0.5 jet mean flow obtained from experimental measurements. The near-field one-way Euler results are similar to those obtained using a previous spatial marching technique called the parabolized stability equations. However, the one-way Euler solutions also include the acoustic fields. With further development, the results suggest that the one-way Euler equation could be used to obtain improved accuracy over the parabolized stability equations as a low-order jet noise model.",
"date": "2014-06-13",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190712-112322396",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190712-112322396",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Office of Naval Research (ONR)",
"grant_number": "N0014-11-1-0753"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2014-2903",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2014-2903",
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"pub_year": "2014",
"author_list": "Towne, Aaron and Colonius, Tim"
},
{
"id": "https://authors.library.caltech.edu/records/zgg2x-nbk43",
"eprint_id": 97114,
"eprint_status": "archive",
"datestamp": "2023-08-20 01:25:35",
"lastmod": "2023-10-20 21:57:31",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Tsai-Hsieh-Chen",
"name": {
"family": "Tsai",
"given": "Hsieh-Chen"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Coriolis Effect on Dynamic Stall in a Vertical Axis Wind Turbine at Moderate Reynolds Number",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aerodynamics, Fluids and Thermal Sciences",
"note": "\u00a9 2014 by Hsieh-Chen Tsai. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 13 Jun 2014. \n\nThis project is sponsored by the Caltech Field Laboratory for Optimized Wind Energy with Prof. John Dabiri as PI under the support of the Gordon and Betty Moore Foundation. We would like to thank Profs. John Dabiri and Beverley McKeon and Mr. Reeve Dunne for their helpful comments on our work.\n\nPublished - TsaiColonius2014.pdf
",
"abstract": "The immersed boundary method is used to simulate the flow around a two-dimensional rotating NACA 0018 airfoil at sub-scale Reynolds number in order to investigate the separated flow occurring on a vertical-axis wind turbine. The influence of dynamic stall on the forces is characterized as a function of tip-speed ratio. The influence of the Coriolis effect is also investigated by comparing the rotating airfoil to one undergoing a equivalent planar motion, which is composed of surging and pitching motions that produce an equivalent speed and angle-of-attack variation over the cycle. When the angle of attack of a rotating airfoil starts to decrease in the upwind half cycle, the Coriolis force leads to a wake-capturing phenomenon of a vortex pair at low tip-speed ratio. This effects occurs at a slightly different phase in each cycle and leads to a significant decrease in the average lift during the downstroke phase. Moreover, the wake-capturing is only observed when the combination of surging, pitching, and Coriolis force are present. Finally, an actuator model is placed at an appropriate location on the suction side of the airfoil surface to control the wake-capturing phenomenon. Based on preliminary simulations, a momentum coefficient above 0.02 was able to increase the average lift by more than 70% over the upwind-half cycle.",
"date": "2014-06-13",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190712-112322314",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190712-112322314",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Gordon and Betty Moore Foundation"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2014-3140",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2014-3140",
"primary_object": {
"basename": "TsaiColonius2014.pdf",
"url": "https://authors.library.caltech.edu/records/zgg2x-nbk43/files/TsaiColonius2014.pdf"
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"pub_year": "2014",
"author_list": "Tsai, Hsieh-Chen and Colonius, Tim"
},
{
"id": "https://authors.library.caltech.edu/records/143xf-j0g84",
"eprint_id": 67395,
"eprint_status": "archive",
"datestamp": "2023-08-19 20:03:04",
"lastmod": "2023-10-18 21:09:00",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Meng-Jomela-Chen-Chen",
"name": {
"family": "Meng",
"given": "Jomela C."
},
"orcid": "0000-0002-8966-2291"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Droplet Breakup in High-Speed Gas Flows",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "breakup, deformation, droplet, shock-cylinder interaction, stripping, unsteady drag coefficient",
"note": "Presented at the \"8th International Conference on Multiphase Flow, ICMF 2013, Jeju, Korea, May 26\u201331, 2013. #2013-488.\n\nAcknowledgments: We are grateful to Vedran Coralic who developed the flow solver and graciously shared the source code with us. Also, thanks to Guillaume Blanquart for his insight and guidance in many useful discussions.\n\nPublished - MengColonius2013-488.pdf
",
"abstract": "Numerical simulations are performed to study the breakup of water cylinders in the flow behind normal shocks. The computational setup is similar to previous experiments (Igra and Takayama, 2001, 2003). We examine the qualitative features of the so-called stripping breakup observed in the numerical results. Two interesting flow features are discussed: the existence of recirculation regions and an upstream jet in the wake. Various integral quantities associated with the cylinder's deformation and acceleration are computed and compared with the experimental results, with generally good agreement. Furthermore, calculations of the velocity and acceleration of the cylinder's center of mass provide an estimate of the unsteady drag coefficient which is approximately constant over the initial breakup period.",
"date": "2013-05-26",
"date_type": "published",
"publisher": "Caltech Library",
"id_number": "CaltechAUTHORS:20160526-114025207",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160526-114025207",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"primary_object": {
"basename": "MengColonius2013-488.pdf",
"url": "https://authors.library.caltech.edu/records/143xf-j0g84/files/MengColonius2013-488.pdf"
},
"resource_type": "conference_item",
"pub_year": "2013",
"author_list": "Meng, Jomela C. and Colonius, Tim"
},
{
"id": "https://authors.library.caltech.edu/records/2mnxf-1rc73",
"eprint_id": 97116,
"eprint_status": "archive",
"datestamp": "2023-08-19 20:02:46",
"lastmod": "2023-10-20 21:57:39",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Towne-A",
"name": {
"family": "Towne",
"given": "Aaron"
},
"orcid": "0000-0002-7315-5375"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Improved Parabolization of the Euler Equations",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 2013 by Aaron Towne and Tim Colonius. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 24 May 2013. \n\nThe authors gratefully acknowledge support from the Office of Naval Research under contract N0014-11-1-0753 with Dr. Brenda Henderson as technical monitor, and from NAVAIR under STTR contract N68335-11-C-0026 with Dr. John Spyropoulos as technical monitor. Additionally, the authors would like to thank Professor Thomas Hagstrom, Southern Methodist University and Professor Peter Schmid, \u00c9cole Polytechnique, for their helpful input on this work.\n\nPublished - TowneColonius2013.pdf
",
"abstract": "We present a new method for stability and modal analysis of shear flows and their acoustic radiation. The Euler equations are modified and solved as a spatial initial value problem in which initial perturbations are specified at the flow inlet and propagated downstream by integration of the equations. The modified equations, which we call one-way Euler equations, differ from the usual Euler equations in that they do not support upstream acoustic waves. It is necessary to remove these modes from the Euler operator because, if retained, they cause instability in the spatial marching procedure. These modes are removed using a two-step process. First, the upstream modes are partially decoupled from the downstream modes using a linear similarity transformation. Second, the error in the first step is eliminated using a convergent recursive filtering technique. A previous spatial marching method called the parabolized stability equations uses numerical damping to stabilize the march, but this has the unintended consequence of heavily damping the downstream acoustic waves. Therefore, the one-way Euler equation could be used to obtain improved accuracy over the parabolized stability equations as a low-order model for noise simulation of mixing layers and jets.",
"date": "2013-05-24",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190712-112322471",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190712-112322471",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Office of Naval Research (ONR)",
"grant_number": "N0014-11-1-0753"
},
{
"agency": "Naval Air Systems Command (NAVAIR)",
"grant_number": "N68335-11-C-0026"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2013-2171",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2013-2171",
"primary_object": {
"basename": "TowneColonius2013.pdf",
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"pub_year": "2013",
"author_list": "Towne, Aaron and Colonius, Tim"
},
{
"id": "https://authors.library.caltech.edu/records/0xxzs-2by21",
"eprint_id": 97112,
"eprint_status": "archive",
"datestamp": "2023-08-19 20:02:40",
"lastmod": "2023-10-20 21:57:24",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Breakey-D-E-S",
"name": {
"family": "Breakey",
"given": "David E. S."
}
},
{
"id": "Jordan-P",
"name": {
"family": "Jordan",
"given": "Peter"
},
"orcid": "0000-0001-8576-5587"
},
{
"id": "Cavalieri-A-V-G",
"name": {
"family": "Cavalieri",
"given": "Andr\u00e9 V. G."
},
"orcid": "0000-0003-4283-0232"
},
{
"id": "Olivier-L\u00e9on",
"name": {
"family": "Olivier",
"given": "L\u00e9on"
}
},
{
"id": "Zhang-Mengqi",
"name": {
"family": "Zhang",
"given": "Mengqi"
}
},
{
"id": "Lehnasch-Guillaume",
"name": {
"family": "Lehnasch",
"given": "Guillaume"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Rodr\u00edguez-D",
"name": {
"family": "Rodr\u00edguez",
"given": "Daniel"
}
}
]
},
"title": "Near-field wavepackets and the far-field sound of a subsonic jet",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 2013 by the author(s). Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 24 May 2013. \n\nD. E. S. Breakey thanks Dr. Craig Meskell for his discussions concerning the analysis of the data. Science Foundation Ireland supported this work under contract 09/RFP/ENM2469. This work was partially supported through the EU\u2013Russian program ORINOCO (FP7-AAT-2010-RTD-Russia; project number 266103) and by the Agence Nationale de la Recherche (ANR) through the project Cool Jazz (COntrol Oriented Linear and non-linear models for Jet AeroacousticZZ).\n\nPublished - BreakeyJordanCavalieriEtAl2013.pdf
",
"abstract": "This paper details the analysis of the relationship between the near-field pressure fluctuations of an unforced, subsonic free jet (0.4 \u2264 M \u2264 0.6) and its low-angle, far-field sound emissions. Azimuthal rings of six microphones recorded pressure fluctuations on a conical surface in the jet near field while an azimuthal ring of three microphones recorded fluctuations in the far field at \u03b8 = 20\u00b0 and R/D = 47.1. Recent measurements have shown close agreement between the velocity fluctuations up to the end of the potential core of the currently studied jet and predictions from the linear Parabolised Stability Equations (PSE), indicating the presence of linear wavepackets in the jet velocity field. Solutions of the Linearised Euler Equations (LEE) reported in the present paper also show good agreement with measurements, and provide a first step toward a time-domain description of the said wavepackets. Though the agreement for PSE in the velocity field breaks down downstream of the potential core, Proper Orthogonal Decomposition (POD) of the current results shows that the wavepackets do persist in this region and are clearly apparent in the near pressure field. Attention is then turned to establishing a relationship between these wavepackets and the radiated sound by comparing simultaneously-obtained measurements of the far-field pressure both directly to the near-field signature as well as to numerical predictions of the far-field emissions available from a recent technique using a tailored Green's function. The direct comparisons are made by correlations between the POD modes and the far-field sound. The first POD mode captures most of the flow energy for the frequency range studied, and the correlation between this mode and the far field is nearly identical to the correlation using the full near-field signal. Higher POD modes also show significant correlation to the far field with a different space\u2013time structure than the first mode. The Green's function predictions are performed both statistically and in the time domain, and though they are shown to be valid for a near-field array with a long axial extent, the experimental limitation of a shorter array (0.5 \u2264 x/D \u2264 8.9), which truncates the wavepacket source in the calculations, causes inaccurate predictions for the experimental data. This error is thought to be the result of a spurious source introduced by the truncation that interferes both constructively and destructively with the wavepacket source. A validation problem shows that this error would be smaller for a higher-M jet.",
"date": "2013-05-24",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190712-112322147",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190712-112322147",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Science Foundation, Ireland",
"grant_number": "09/RFP/ENM2469"
},
{
"agency": "European Research Council (ERC)",
"grant_number": "266103"
},
{
"agency": "Agence Nationale pour la Recherche (ANR)",
"grant_number": "COOLJAZZ"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2013-2083",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2013-2083",
"primary_object": {
"basename": "BreakeyJordanCavalieriEtAl2013.pdf",
"url": "https://authors.library.caltech.edu/records/0xxzs-2by21/files/BreakeyJordanCavalieriEtAl2013.pdf"
},
"resource_type": "conference_item",
"pub_year": "2013",
"author_list": "Breakey, David E. S.; Jordan, Peter; et el."
},
{
"id": "https://authors.library.caltech.edu/records/r38hz-1fy26",
"eprint_id": 97120,
"eprint_status": "archive",
"datestamp": "2023-08-19 20:02:55",
"lastmod": "2023-10-20 21:57:51",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Sinha-A",
"name": {
"family": "Sinha",
"given": "A."
},
"orcid": "0000-0002-7122-3549"
},
{
"id": "Schlinker-R-H",
"name": {
"family": "Schlinker",
"given": "R. H."
}
},
{
"id": "Simonich-J-S",
"name": {
"family": "Simonich",
"given": "J. S."
}
},
{
"id": "Reba-R-A",
"name": {
"family": "Reba",
"given": "R. A."
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "T."
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Toward Active Control of Noise from Hot Supersonic Jets",
"ispublished": "unpub",
"full_text_status": "restricted",
"keywords": "Aeroacoustics",
"note": "\u00a9 2013 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. \n\nPublished Online: 24 May 2013. \n\nThe authors gratefully acknowledge support from the Office of Naval Research under contract N0014-11-1-0753 with Dr. Brenda Henderson as technical monitor, and from NAVAIR under STTR contract N68335-11-C-0026 with Dr. John Spyropoulos as technical monitor.",
"abstract": "We present diagnostic experiments and reduced-order models aimed at understanding and mitigating supersonic jet noise from coherent wavepackets in the turbulent shear layer, generally accepted to be the source of peak aft-angle mixing noise. The work builds on a successful Caltech/UTRC modeling approach that predicts the evolution of the wavepackets as instability waves of the turbulent mean flow, as well as the noise radiated from their near field. The models are experimentally assessed for unforced and forced supersonic isothermal and heated Mach 1.5 jets from ideal expansion nozzles. A spinning valve device is used to inject air near the nozzle lip at frequencies up to a Strouhal number of about 0.25. Results indicate a 2-3 dB benefit near peak frequencies of the spectrum and a 2 dB OASPL reduction at a mass flow percentage of 3.2. For the same injection plenum pressure, steady blowing yields more noise benefit than the unsteady actuation schemes explored until now. However, this may be explained by the slight decrease in injection velocity incurred in going from steady to unsteady operation. The reduced-order models, based on parabolized stability equations (PSE), are found to be in good agreement, in terms of envelope and phase, with those educed from the experimental data of the unforced jet. For the actuation schemes we have considered to date, the model and experimental data support a tentative explanation for the observed noise reduction in terms of attenuation of the wavepacket amplitudes by the thickened shear layer. Wavepackets induced by the harmonic component of the actuation are linearly superposed on those produced by broadband turbulence, without significant interaction, such that they lead to the addition of tones to the far-field noise that are counterproductive as far as noise reduction is concerned.",
"date": "2013-05-24",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190712-112322809",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190712-112322809",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Office of Naval Research (ONR)",
"grant_number": "N0014-11-1-0753"
},
{
"agency": "Naval Air Systems Command (NAVAIR)",
"grant_number": "N68335-11-C-0026"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2013-2234",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2013-2234",
"resource_type": "conference_item",
"pub_year": "2013",
"author_list": "Sinha, A.; Schlinker, R. H.; et el."
},
{
"id": "https://authors.library.caltech.edu/records/a6nxm-dhj24",
"eprint_id": 97127,
"eprint_status": "archive",
"datestamp": "2023-08-19 20:02:59",
"lastmod": "2023-10-20 21:58:27",
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"creators": {
"items": [
{
"id": "Rodr\u00edguez-D",
"name": {
"family": "Rodr\u00edguez",
"given": "Daniel"
}
},
{
"id": "Cavalieri-A-V-G",
"name": {
"family": "Cavalieri",
"given": "Andr\u00e9 V. G."
},
"orcid": "0000-0003-4283-0232"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Jordan-P",
"name": {
"family": "Jordan",
"given": "Peter"
},
"orcid": "0000-0001-8576-5587"
}
]
},
"title": "Wavepacket eduction in turbulent jets based on eigenmode decomposition of PIV data",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 2013 American Institute of Aeronautics and Astronautics. \n\nPublished Online: 24 May 2013. \n\nWe thank Drs. Kristjan Gudmundsson, Arnab Samanta and Aniruddha Sinha for their contributions on the development of the PSE code and Carine Fourment-Cazenave, Patrick Braud and Dr. Jo\u00ebl Delville for their work during the experiments. The work of D. Rodr\u00edguez was supported by the EU Marie Curie COFUND program.\n\nPublished - RodriguezCavalieriColoniusEtAl2013.pdf
",
"abstract": "The dynamics of large scale structures in unforced turbulent jets at subsonic speeds have been related to the generation of the peak noise radiated the aft direction. The utility of instability wavepackets computed by linear stability theory or parabolised stability equations (PSE) have been demonstrated for the modeling of the near-field pressure fluctuations associated with the coherent structures. In this paper, we investigate whether the velocity field corresponding to the wavepackets also represents adequately that of the coherent structures. Previous research showed remarkable agreement in the velocity field up to the end of the potential core, but the agreement is lost gradually downstream.\n\nLocally-parallel linear stability theory (LST) of jet velocity profiles is revisited to further study the evolution of the wavepackets and the manner in which PSE models them. An adjoint-based eigenmode decomposition technique is used to project cross-sectional velocity profiles measured using time-resolved particle image velocimetry (PIV) on the Kelvin-Helmholtz eigenmode responsible for the wavepacket amplification. The instability wave thus extracted is then compared, both in amplification and shape, to the PSE wavepacket and to the dominant coherent structures obtained from the proper orthogonal decomposition of the PIV measurements. The comparisons between PSE models and POD-filtered fluctuations define three spatial regions along the streamwise direction that are explained in terms of changes in the LST eigenspectrum.",
"date": "2013-05-24",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190712-112323422",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190712-112323422",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Marie Curie Fellowship"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2013-2084",
"name": "AIAA Paper"
}
]
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"doi": "10.2514/6.2013-2084",
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"basename": "RodriguezCavalieriColoniusEtAl2013.pdf",
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"author_list": "Rodr\u00edguez, Daniel; Cavalieri, Andr\u00e9 V. G.; et el."
},
{
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"datestamp": "2023-08-19 20:00:23",
"lastmod": "2023-10-20 21:58:11",
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"items": [
{
"id": "Rodr\u00edguez-D",
"name": {
"family": "Rodr\u00edguez",
"given": "Daniel"
}
},
{
"id": "Sinha-A",
"name": {
"family": "Sinha",
"given": "Aniruddha"
},
"orcid": "0000-0002-7122-3549"
},
{
"id": "Br\u00e8s-G-A",
"name": {
"family": "Br\u00e8s",
"given": "Guillaume A."
},
"orcid": "0000-0003-2507-8659"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Acoustic field associated with parabolized stability equation models in turbulent jets",
"ispublished": "unpub",
"full_text_status": "restricted",
"keywords": "Aeroacoustics",
"note": "\u00a9 2013 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. \n\nPublished Online: 24 May 2013. \n\nThis work was sponsored in part by the U.S. Navy Naval Air Systems Command (Contract N68335-11-C0026) and by the Office of Naval Research (Grant N0014-11-1-0753). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the sponsoring agencies. The LES calculations were carried out on CRAY XE6 machines at DoD supercomputer facilities in ERDC and AFRL. D. Rodr\u00edguez acknowledges funding from the Marie Curie - COFUND-UNITE programme.",
"abstract": "Wavepackets are large-scale turbulent structures that are correlated and advected over distances that are large compared to the integral scales of turbulence, and have been shown to be responsible for the peak noise radiated at aft angles to the jet axis. The present paper discusses linear models of these wavepackets for supersonic turbulent jets based on Parabolized Stability Equations (PSE). In the past, results of this approach were shown to be in excellent agreement with coherent structures extracted from experimental near-field pressure and velocity data in subsonic jets. Here, we make use of a Large Eddy Simulation (LES) database for an isothermal and a moderately heated Mach 1.5 turbulent jets. Careful comparisons of the PSE models with near-field pressure fields from LES, filtered by means of Proper Orthogonal Decomposition (POD), demonstrate acceptable fidelity of the model. Finally, the acoustic far-field associated with the PSE wavepackets is computed using a Kirchhoff surface method, capturing reasonably well the far-field pressure at angles close to the peak.",
"date": "2013-05-23",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190712-112323164",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190712-112323164",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Naval Air Systems Command (NAVAIR)",
"grant_number": "N68335-11-C0026"
},
{
"agency": "Office of Naval Research (ONR)",
"grant_number": "N0014-11-1-0753"
},
{
"agency": "Marie Curie Fellowship"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2013-2279",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2013-2279",
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"pub_year": "2013",
"author_list": "Rodr\u00edguez, Daniel; Sinha, Aniruddha; et el."
},
{
"id": "https://authors.library.caltech.edu/records/d9vec-4a623",
"eprint_id": 97107,
"eprint_status": "archive",
"datestamp": "2023-08-19 14:18:07",
"lastmod": "2023-10-20 21:57:05",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Choi-Jeesoon",
"name": {
"family": "Choi",
"given": "Jeesoon"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Williams-D",
"name": {
"family": "Williams",
"given": "David"
}
}
]
},
"title": "Dynamics and Energy Extraction of a Surging and Plunging Airfoil at Low Reynolds Number",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aerospace Systems, Operations and Life Cycle",
"note": "\u00a9 2013 American Institute of Aeronautics and Astronautics. \n\nPublished Online: 5 Jan 2013. \n\nThis work was supported by the Air Force Office of Scientific Research (FA950-09-1-0189).\n\nSubmitted - ChoiColoniusWilliams2013.pdf
",
"abstract": "We investigate the unsteady aerodynamic forces and energy transfer associated with harmonic surging (streamwise) and plunging (transverse) motion of a thin airfoil at low Reynolds number. Two-dimensional unsteady flows are simulated over a large range of amplitude and reduced-frequency of the oscillatory motion using the immersed boundary projection method, and the computational results are compared to inviscid flow models and experiments. At low angle of attack there is reasonable agreement with inviscid theory for the amplitude and phase of lift fluctuations, despite the low Reynolds number. At high angle of attack, the separated flow leads to larger lift and drag fluctuations not captured by inviscid models. At frequencies below the vortex shedding frequency, lift fluctuations are first enhanced and then attenuated depending on the phase between the freestream velocity and the forming leading-edge vortex. Resonance with the vortex shedding frequency also occurs. The time-averaged forces and power supplied by the oscillating airfoil are also evaluated to find frequency ranges that are favorable for the airfoil.",
"date": "2013-01-05",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190712-112321331",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190712-112321331",
"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": "FA950-09-1-0189"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2013-0672",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2013-672",
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"basename": "ChoiColoniusWilliams2013.pdf",
"url": "https://authors.library.caltech.edu/records/d9vec-4a623/files/ChoiColoniusWilliams2013.pdf"
},
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"pub_year": "2013",
"author_list": "Choi, Jeesoon; Colonius, Tim; et el."
},
{
"id": "https://authors.library.caltech.edu/records/vwpsz-ree22",
"eprint_id": 97098,
"eprint_status": "archive",
"datestamp": "2023-08-19 13:27:55",
"lastmod": "2023-10-20 21:56:40",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Jang-Chang-Young",
"name": {
"family": "Jang",
"given": "Chang Young"
}
},
{
"id": "Appel\u00f6-D",
"name": {
"family": "Appel\u00f6",
"given": "Daniel"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Hagstrom-T",
"name": {
"family": "Hagstrom",
"given": "Thomas"
}
},
{
"id": "Inkman-M",
"name": {
"family": "Inkman",
"given": "Matthew"
}
}
]
},
"title": "An Analysis of Dispersion and Dissipation Properties of Hermite Methods and Its Application to Direct Numerical Simulation of Jet Noise",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 2012 by Daniel Appel\u00f6. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 11 Nov 2012. \n\nThis material is based upon work supported, in part, by the National Science Foundation under Grants OCI-0905045 and OCI-0904773 and, in part, by ARO grant W911NF-09-1-0344. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.\n\nSubmitted - JangAppeloeColoniusEtAl2012.pdf
",
"abstract": "The dissipative and dispersive properties of Hermite methods are analyzed by a modified equation approach and by direct computation of the dispersion relations for the discrete modes of the scheme. The two approaches lead to the same results for well-resolved modes but are quantitatively different at the finest scales. The resolution requirements, obtained from the analysis, for Hermite schemes are compared to those of typical high-resolution difference formulas. The results from the analysis are also used to predict the resolution requirements for a simulation at Re \u223c 3600. The validity of the prediction is confirmed by numerical experiments.",
"date": "2012-11-11",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190712-112320535",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190712-112320535",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "NSF",
"grant_number": "OCI-0905045"
},
{
"agency": "NSF",
"grant_number": "OCI-0904773"
},
{
"agency": "Army Research Office (ARO)",
"grant_number": "W911NF-09-1-0344"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2012-2240",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2012-2240",
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"basename": "JangAppeloeColoniusEtAl2012.pdf",
"url": "https://authors.library.caltech.edu/records/vwpsz-ree22/files/JangAppeloeColoniusEtAl2012.pdf"
},
"resource_type": "conference_item",
"pub_year": "2012",
"author_list": "Jang, Chang Young; Appel\u00f6, Daniel; et el."
},
{
"id": "https://authors.library.caltech.edu/records/62n9f-7f238",
"eprint_id": 97106,
"eprint_status": "archive",
"datestamp": "2023-08-19 13:28:00",
"lastmod": "2023-10-20 21:57:01",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Cavalieri-A-V-G",
"name": {
"family": "Cavalieri",
"given": "Andr\u00e9 V. G."
},
"orcid": "0000-0003-4283-0232"
},
{
"id": "Violato-D",
"name": {
"family": "Violato",
"given": "Daniele"
}
},
{
"id": "Rodr\u00edguez-D",
"name": {
"family": "Rodr\u00edguez",
"given": "Daniel"
}
},
{
"id": "Jordan-P",
"name": {
"family": "Jordan",
"given": "Peter"
},
"orcid": "0000-0001-8576-5587"
},
{
"id": "Scarano-F",
"name": {
"family": "Scarano",
"given": "Fulvio"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Gervais-Y",
"name": {
"family": "Gervais",
"given": "Yves"
}
}
]
},
"title": "Low-speed jet dynamics and sound radiation",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 2012 by Peter Jordan. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 11 Nov 2012. \n\nThe authors kindly acknowledge LaVision GmbH and Piero Colonna for providing the CMOS cameras used in the TOMO-PIV experiments. \n\nThis work was conducted as part of the FLOVIST project (Flow Visualization Inspired Aeroacoustics with Time Resolved Tomographic Particle Image Velocimetry), funded by the European Research Council (ERC), grant no 202887. This present work was partially supported by CNPq, National Council of Scientific and Technological Development \u2013 Brazil, and through the EU-Russian program ORINOCO (FP7-AAT-2010-RTD-Russia; project number 266103).\n\nSubmitted - CavalieriViolatoRodriguezEtAl2012.pdf
",
"abstract": "Experimental velocity measurements of a low-speed jet, performed using time-resolved tomographic PIV, are used to study the dynamics of large-scale structures and their sound radiation. The experimental results show the roll-up of axisymmetric vortices that pair downstream, and subsequently lose their azimuthal coherence. Models of linear instability waves using both steady laminar and mean-field base flows flow are applied. While good agreement can be obtained for the vortex roll-up frequency in the near-nozzle region using the laminar base flow, non-linear effects must be included, via the mean field, in order to capture the downstream evolution of both the fundamental and subharmonic (vortex pairing). The velocity fluctuations for both frequencies have a wave-packet structure with some jitter in the form of modulations of the spatial extent and amplitude of the envelope. The sound radiation is modelled using a jittering wave-packet model, an shows agreement with the exponential directivity shape of Laufer and Yen (J. Fluid Mech. 134, 1983).",
"date": "2012-11-11",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190712-112321277",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190712-112321277",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "European Research Council (ERC)",
"grant_number": "202887"
},
{
"agency": "Conselho Nacional de Desenvolvimento Cient\u00edfico e Tecnol\u00f3gico (CNPq)"
},
{
"agency": "European Research Council (ERC)",
"grant_number": "266103"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2012-2080",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2012-2080",
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"basename": "CavalieriViolatoRodriguezEtAl2012.pdf",
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},
"resource_type": "conference_item",
"pub_year": "2012",
"author_list": "Cavalieri, Andr\u00e9 V. G.; Violato, Daniele; et el."
},
{
"id": "https://authors.library.caltech.edu/records/3err5-ynj11",
"eprint_id": 97125,
"eprint_status": "archive",
"datestamp": "2023-08-19 13:28:09",
"lastmod": "2023-10-20 21:58:19",
"type": "conference_item",
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"creators": {
"items": [
{
"id": "Rodr\u00edguez-D",
"name": {
"family": "Rodr\u00edguez",
"given": "Daniel"
}
},
{
"id": "Sinha-A",
"name": {
"family": "Sinha",
"given": "Aniruddha"
},
"orcid": "0000-0002-7122-3549"
},
{
"id": "Br\u00e8s-G-A",
"name": {
"family": "Br\u00e8s",
"given": "Guillaume A."
},
"orcid": "0000-0003-2507-8659"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Parabolized stability equation models in turbulent supersonic jets",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 2012 American Institute of Aeronautics and Astronautics. \n\nPublished Online: 11 Nov 2012. \n\nThis work was supported by NAVAIR through an STTR grant N68335-11-C-0026 to Cascade Technologies, Inc. and by ONR Grant N00014-11-1-0753. The authors would like to thank Dr. Joseph W. Nichols and Prof. Sanjiva K. Lele, of Stanford University, for their contributions to the LES efforts and their inputs on global modes. The LES calculations were carried out on CRAY XE6 machines at DoD supercomputer facilities in ERDC and AFRL.\n\nSubmitted - RodriguezSinhaBresEtAl2012.pdf
",
"abstract": "The peak noise radiation in the aft direction of high-speed, turbulent jets has been linked to the dynamics of the large-scale structures. We use the parabolized stability equations (PSE) to model these structures as wavepackets associated with instability of the turbulent mean flow. Our past work has demonstrated the utility of these models for subsonic jets; in the present work we extend these methods to supersonic jets. A large eddy simulation database corresponding to an unheated, ideally-expanded Mach 1.5 jet with Reynolds number of 300,000 is employed to extract the necessary input for the PSE (the mean flow and initial conditions) and also to perform comparisons and validations of the computed wavepackets.\n\nBy contrast with subsonic jets, when the jet exit velocity is supersonic with respect to the ambient speed of sound, linear stability theory predicts that multiple instability modes, related to resonance of pressure waves within the potential core, can be present in addition to the inflectional instability. The possible coexistence of different instability mechanisms, the determination of adequate inlet conditions, and their effect on the wavepackets computed are investigated here.\n\nWe compare the wavepackets predicted by PSE with fluctuations extracted from the LES data. When performing comparisons, filtering techniques need to be employed in order to extract the coherent, low frequency structures associated with wavepackets. Largescale fluctuations educed using cross-correlation techniques, such as the proper orthogonal decomposition, are shown to compare reasonably well with the PSE wavepackets, but by contrast with subsonic jets, it appears that several POD modes are required to represent the PSE-predicted wavepacket.",
"date": "2012-11-11",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190712-112323257",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190712-112323257",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Naval Air Systems Command (NAVAIR)",
"grant_number": "N68335-11-C-0026"
},
{
"agency": "Office of Naval Research (ONR)",
"grant_number": "N00014-11-1-0753"
}
]
},
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"id": "2012-2117",
"name": "AIAA Paper"
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"doi": "10.2514/6.2012-2117",
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"basename": "RodriguezSinhaBresEtAl2012.pdf",
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},
"resource_type": "conference_item",
"pub_year": "2012",
"author_list": "Rodr\u00edguez, Daniel; Sinha, Aniruddha; et el."
},
{
"id": "https://authors.library.caltech.edu/records/vpge7-w5b95",
"eprint_id": 97108,
"eprint_status": "archive",
"datestamp": "2023-08-19 13:28:05",
"lastmod": "2023-10-20 21:57:09",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Cavalieri-A-V-G",
"name": {
"family": "Cavalieri",
"given": "Andr\u00e9 V. G."
},
"orcid": "0000-0003-4283-0232"
},
{
"id": "Rodr\u00edguez-D",
"name": {
"family": "Rodr\u00edguez",
"given": "Daniel"
}
},
{
"id": "Jordan-P",
"name": {
"family": "Jordan",
"given": "Peter"
},
"orcid": "0000-0001-8576-5587"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Gervais-Y",
"name": {
"family": "Gervais",
"given": "Yves"
}
}
]
},
"title": "Wavepackets in the velocity field of turbulent jets",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 2012 by Peter Jordan. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 11 Nov 2012. \n\nWe thank Carine Fourment-Cazenave, Patrick Braud and Jo\u00ebl Delville for their work during the experiments. This work was supported by CNPq, National Council of Scientific and Technological Development \u2013 Brazil, and through the EU-Russian program ORINOCO (FP7-AAT-2010-RTD-Russia; project number 266103).\n\nSubmitted - CavalieriRodriguezJordanEtAl2012.pdf
",
"abstract": "We study the velocity field of unforced, high Reynolds number, subsonic jets, issuing from round nozzles with turbulent boundary layers. The objective of the study is to discern the presence of instability waves in such flows and to explore their relationship with the radiated sound. The velocity field is measured using a hot-wire anemometer and a stereoscopic, time-resolved, PIV system, the latter being setup so as to measure three components of velocity in cross-stream planes; the field can thereby be decomposed into frequency and azimuthal Fourier modes. The low-angle sound radiation is measured, synchronously with the PIV acquisition, using a microphone ring array at polar angle, \u03b8 = 20\u00b0 (measured with respect to the downstream jet axis).\n\nConsistent with previous observations, the azimuthal wavenumber spectra of the velocity and acoustic pressure fields are quite different. The velocity spectrum exhibits a peak at higher azimuthal wavenumber and the peak is found to scale with the local momentum thickness of the mixing layer. The acoustic pressure field is, on the other hand, predominantly axisymmetric, suggesting an increased relative acoustic efficiency of the axisymmetric mode of the velocity field, a characteristic that can be shown, theoretically, to be due to the radial compactness of the flow. This is confirmed by significant correlations, around 10%, between the axisymmetric modes of the velocity and acoustic pressure fields, these values being significantly higher than those previously reported for two-point flow-acoustic correlations in subsonic jets. The axisymmetric and first helical modes of the velocity field are then compared with solutions of linear Parabolised Stability Equations (PSE) (where the experimental mean velocity field is used as the base flow) to ascertain if these modes correspond to linear instability waves. For all but the lowest frequencies close agreement is obtained for the spatial amplification, up to the end of the potential core. The radial shapes of the linear PSE results also agree with the experimental results over the same region. The results suggests that, despite the broadband character of the turbulence of these unforced jets, the evolution of a certain range of frequencies and azimuthal modes can be modelled as linear instabilities of the mean velocity profile, and that these instabilities are associated with the sound radiated at low polar angles.",
"date": "2012-11-11",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190712-112321414",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190712-112321414",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Conselho Nacional de Desenvolvimento Cient\u00edfico e Tecnol\u00f3gico (CNPq)"
},
{
"agency": "European Research Council (ERC)",
"grant_number": "266103"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2012-2115",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2012-2115",
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"basename": "CavalieriRodriguezJordanEtAl2012.pdf",
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"pub_year": "2012",
"author_list": "Cavalieri, Andr\u00e9 V. G.; Rodr\u00edguez, Daniel; et el."
},
{
"id": "https://authors.library.caltech.edu/records/hne5z-85q52",
"eprint_id": 97128,
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"datestamp": "2023-08-19 12:39:24",
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"type": "conference_item",
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"creators": {
"items": [
{
"id": "Regele-J-D",
"name": {
"family": "Regele",
"given": "J. D."
}
},
{
"id": "Rabinovitch-J",
"name": {
"family": "Rabinovitch",
"given": "J."
},
"orcid": "0000-0002-1914-7964"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "T."
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Blanquart-G",
"name": {
"family": "Blanquart",
"given": "G."
},
"orcid": "0000-0002-5074-9728"
}
]
},
"title": "Numerical Modeling and Analysis of Early Shock Wave Interactions with a Dense Particle Cloud",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Fluid Dynamics",
"note": "\u00a9 2012 by Jonathan Regele. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 6 Sep 2012. \n\nThe authors would like to thank Karen Oren for her contribution to this work.\n\nPublished - RegeleRabinovitchColoniusEtAl2012.pdf
",
"abstract": "Dense compressible multiphase flows exist in variable phase turbines, explosions, and fluidized beds, where the particle volume fraction is in the range 0.001 < \u03b1_d < 0.5. A simple model problem that can be used to study modeling issues related to these types of flows is a shock wave impacting a particle cloud. In order to characterize the initial shock-particle interactions when there is little particle movement, a two-dimensional (2-D) model problem is created where the particles are frozen in place. Qualitative comparison with experimental data indicates that the 2-D model captures the essential flow physics. Volume-averaging of the 2-D data is used to reduce the data to one dimension, and x-t diagrams are used to characterize the flow behavior. An equivalent one-dimensional (1-D) model problem is developed for direct comparison with the 2-D model. While the 1-D model characterizes the overall steady-state flow behavior well, it fails to capture aspects of the unsteady behavior. As might be expected, it is found that neglecting the unclosed fluctuation terms inherent in the volume-averaged equations is not appropriate for dense gas-particle flows.",
"date": "2012-09-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190712-112323497",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190712-112323497",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"other_numbering_system": {
"items": [
{
"id": "2012-3161",
"name": "AIAA Paper"
}
]
},
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}
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"doi": "10.2514/6.2012-3161",
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},
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"pub_year": "2012",
"author_list": "Regele, J. D.; Rabinovitch, J.; et el."
},
{
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"datestamp": "2023-08-22 05:27:19",
"lastmod": "2023-10-23 16:20:10",
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"creators": {
"items": [
{
"id": "Hagstrom-T",
"name": {
"family": "Hagstrom",
"given": "Thomas"
}
},
{
"id": "Appel\u00f6-D",
"name": {
"family": "Appel\u00f6",
"given": "Daniel"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Inkman-M",
"name": {
"family": "Inkman",
"given": "Matthew"
}
},
{
"id": "Jang-Chang-Young",
"name": {
"family": "Jang",
"given": "Chang Young"
}
}
]
},
"title": "Simulation of compressible flows using Hermite methods",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics; Fluid flows; Numerical methods; Computational fluid dynamics",
"note": "\u00a9 Acoustical Society of America. \n\nPublished Online: 12 April 2012.",
"abstract": "Spectral element methods based on Hermite interpolation have a number of unique properties. First of all, the stabilization inherent in the interpolation process is sufficient to suppress nonlinear instabilities observed with other discretization schemes and leads to accurate linear transport of nonsmooth solutions. Second, and most important, they allow purely local time-stepping procedures limited only by geometric domain-of-dependence requirements. Thus high-order Hermite methods maximize the computation-to-communication ratio and therefore they admit highly efficient implementations on multicore processors. In this talk we focus on the application of Hermite methods to simulate unsteady compressible flows. Examples will include the direct simulation of the aeroacoustics of a low Reynolds number subsonic jet, as well as studies of more basic sound radiating flows. The latter will illustrate the coupling of Hermite methods with more standard discontinuous Galerkin discretizations to handle physical boundaries.",
"date": "2012-04-12",
"date_type": "published",
"id_number": "CaltechAUTHORS:20190712-112320617",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190712-112320617",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"doi": "10.1121/1.4708863",
"resource_type": "conference_item",
"pub_year": "2012",
"author_list": "Hagstrom, Thomas; Appel\u00f6, Daniel; et el."
},
{
"id": "https://authors.library.caltech.edu/records/9mnz8-y5059",
"eprint_id": 28549,
"eprint_status": "archive",
"datestamp": "2023-08-19 02:24:44",
"lastmod": "2023-10-24 17:58:44",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Ando-Keita",
"name": {
"family": "Ando",
"given": "K."
}
},
{
"id": "Sanada-T",
"name": {
"family": "Sanada",
"given": "T."
}
},
{
"id": "Inaba-Kazuaki",
"name": {
"family": "Inaba",
"given": "K."
}
},
{
"id": "Shepherd-J-E",
"name": {
"family": "Shepherd",
"given": "J. E."
},
"orcid": "0000-0003-3181-9310"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "T."
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Brennen-C-E",
"name": {
"family": "Brennen",
"given": "C. E."
}
}
]
},
"title": "Shock Theory of a Bubbly Liquid in a Deformable Tube",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Fluid-structure interaction, bubbly water hammer",
"note": "The authors would like to express their thanks to\nT. Nishiyama for his help with the experimentation, J. S.\nDamazo and R. Porowski for the bubble images, and\nS. Hori for his observations about the experimental data.\nThis work was supported by ONR Grant No. N00014-06-1-0730.\n\nAccepted Version - AndoSISCB-ICMF2010.pdf
",
"abstract": "Shock propagation through a bubbly liquid filled in a deformable cylindrical tube is considered. Quasi-one-dimensional\nbubbly flow equations that include fluid-structure interaction are formulated, and the steady shock\nrelations are derived. Experiments are conducted in which a free-falling steel projectile impacts the top of an air/water\nmixture in a polycarbonate tube, and stress waves in the tube material are measured. The experimental data indicate\nthat the linear theory cannot properly predict the propagation speeds of shock waves in mixture-filled tubes; the shock\ntheory is found to more accurately estimate the measured wave speeds.",
"date": "2011-12-21",
"date_type": "published",
"publisher": "Caltech Library",
"id_number": "CaltechAUTHORS:20111221-123516479",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20111221-123516479",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Office of Naval Research (ONR)",
"grant_number": "N00014-06-1-0730"
}
]
},
"local_group": {
"items": [
{
"id": "GALCIT"
}
]
},
"primary_object": {
"basename": "AndoSISCB-ICMF2010.pdf",
"url": "https://authors.library.caltech.edu/records/9mnz8-y5059/files/AndoSISCB-ICMF2010.pdf"
},
"resource_type": "conference_item",
"pub_year": "2011",
"author_list": "Ando, K.; Sanada, T.; et el."
},
{
"id": "https://authors.library.caltech.edu/records/f8vna-mxz22",
"eprint_id": 28453,
"eprint_status": "archive",
"datestamp": "2023-08-20 02:26:39",
"lastmod": "2023-10-24 17:54:38",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Ando-Keita",
"name": {
"family": "Ando",
"given": "Keita"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Brennen-C-E",
"name": {
"family": "Brennen",
"given": "Christopher E."
}
}
]
},
"title": "Shock propagation in polydisperse bubbly flows",
"ispublished": "unpub",
"full_text_status": "public",
"note": "Copyright \u00a9 2009 by ASME. \n\nCAV2009 \u2013 Paper No. 172\n\nSubmitted - AND245.pdf
",
"abstract": "The effect of distributed bubble size on shock propagation\nin homogeneous bubbly liquids is computed using a continuum\ntwo-phase model. An ensemble-averaging technique is employed\nto derive the statistically averaged equations and a finite-volume\nmethod is used to solve the model equations. The bubble\ndynamics are incorporated using a Rayleigh-Plesset-type equation\nwhich includes the effects of heat transfer, liquid viscosity\nand compressibility. For the case of monodisperse bubbles, it is\nknown that relaxation oscillations occur behind the shock due to\nthe bubble dynamics. The present computations for the case of\npolydisperse bubbles show that bubble size distributions lead to\nadditional damping of the shock dynamics. If the distribution is\nsufficiently broad, the statistical effect dominates over the physical\ndamping associated with the single bubble dynamics. This\nsmooths out the oscillatory shock structure.",
"date": "2011-12-13",
"date_type": "published",
"publisher": "Caltech Library",
"id_number": "CaltechAUTHORS:20111213-124427981",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20111213-124427981",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"other_numbering_system": {
"items": [
{
"id": "172",
"name": "CAV2009"
}
]
},
"primary_object": {
"basename": "AND245.pdf",
"url": "https://authors.library.caltech.edu/records/f8vna-mxz22/files/AND245.pdf"
},
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"pub_year": "2011",
"author_list": "Ando, Keita; Colonius, Tim; et el."
},
{
"id": "https://authors.library.caltech.edu/records/0bwnw-d3f06",
"eprint_id": 97201,
"eprint_status": "archive",
"datestamp": "2023-08-19 07:58:23",
"lastmod": "2023-10-20 22:03:12",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Feldman-Yu",
"name": {
"family": "Feldman",
"given": "Yu."
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "T."
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Pauken-M-T",
"name": {
"family": "Pauken",
"given": "M."
},
"orcid": "0000-0002-3993-675X"
},
{
"id": "Hall-J-L",
"name": {
"family": "Hall",
"given": "J. L."
}
},
{
"id": "Jones-J-A",
"name": {
"family": "Jones",
"given": "J. A."
}
}
]
},
"title": "Numerical and Experimental Modeling of Natural Convection for a Cryogenic Prototype of a Titan Montgolfiere",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aviation Technology, Integration, and Operations",
"note": "\u00a9 2011 by the American Institute of Aeronautics and Astronautics, Inc. \n\nPublished Online: 4 Jun 2012. \n\nPart of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. The help and support of the engineering and technical staff of Wyle Labs in El Segundo and their cryogenic chamber facility during the experiment is greatly acknowledged.\n\nSubmitted - FeldmanSamantaColoniusEtAl2011.pdf
",
"abstract": "Natural convection in a spherical geometry is considered for prediction of the buoyancy characteristics of one meter diameter single- and double-walled balloons in a cryogenic environment. The steady-state flow characteristics obtained by solving the Reynolds-Averaged Navier Stokes equations (RANS) with a standard k-\u03b5 model are used to determine the balloon performance in terms of net buoyancy as a function of heat input. Thermal radiation effects on the overall balloon performance are also investigated. The results obtained compared favorably with the corresponding cryogenic experiments conducted at the same scale in a cryogenic facility. In addition, both numerical and experimental results were compared with engineering heat transfer correlations used in system-level models of the Titan Montgolfiere. Finally, we examine scaling issues for the full-scale Titan Montgolfieres.",
"date": "2011-09",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190717-102319028",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190717-102319028",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "JPL/Caltech/NASA"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2011-6869",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2011-6869",
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"basename": "FeldmanSamantaColoniusEtAl2011.pdf",
"url": "https://authors.library.caltech.edu/records/0bwnw-d3f06/files/FeldmanSamantaColoniusEtAl2011.pdf"
},
"resource_type": "conference_item",
"pub_year": "2011",
"author_list": "Feldman, Yu.; Colonius, T.; et el."
},
{
"id": "https://authors.library.caltech.edu/records/pgrpf-cnv25",
"eprint_id": 97100,
"eprint_status": "archive",
"datestamp": "2023-08-19 07:03:23",
"lastmod": "2023-10-20 21:56:44",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Hartmann-D",
"name": {
"family": "Hartmann",
"given": "Daniel"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "A projection method for multiphase flows",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Computational Fluid Dynamics",
"note": "\u00a9 2011 by Daniel Hartmann. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 14 Jun 2012. \n\nD.H. is sponsored by the German Research Association (Deutsche Forschungsgemeinschaft (DFG)) under grant HA 5535/2-1. The support is gratefully acknowledged.\n\nSubmitted - HartmannColonius2011.pdf
",
"abstract": "An Eulerian projection approach for incompressible variable-density two-phase flows is presented. The Navier-Stokes equations governing these flows are reformulated to take the form of the corresponding equations for the lighter phase with a constant density, which can be efficiently solved using standard numerical methods. The effect of the additional mass in the heavier phase is accounted for by a forcing term, which is determined from the solution of an artificial velocity field. This artificial field is subjected solely to inertial and gravity forces as well as the force coupling the flow field and the artificial field. The phase interface in this purely Eulerian approach is described using the level-set method. Results for two-dimensional simulations of the Rayleigh-Taylor instability are presented to validate the new method.",
"date": "2011-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190712-112320713",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190712-112320713",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Deutsche Forschungsgemeinschaft (DFG)",
"grant_number": "HA 5535/2-1"
}
]
},
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"id": "2011-3831",
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}
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"url": "https://authors.library.caltech.edu/records/pgrpf-cnv25/files/HartmannColonius2011.pdf"
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"pub_year": "2011",
"author_list": "Hartmann, Daniel and Colonius, Tim"
},
{
"id": "https://authors.library.caltech.edu/records/s1mnq-rnw88",
"eprint_id": 97203,
"eprint_status": "archive",
"datestamp": "2023-08-19 07:03:38",
"lastmod": "2023-10-20 22:03:19",
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"creators": {
"items": [
{
"id": "Cavalieri-A-V-G",
"name": {
"family": "Cavalieri",
"given": "Andr\u00e9 V. G."
},
"orcid": "0000-0003-4283-0232"
},
{
"id": "Jordan-P",
"name": {
"family": "Jordan",
"given": "Peter"
},
"orcid": "0000-0001-8576-5587"
},
{
"id": "Gervais-Y",
"name": {
"family": "Gervais",
"given": "Yves"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Axisymmetric superdirectivity in subsonic jets",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 2011 by the author(s). Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 4 Nov 2012. \n\nThe present work is partially supported by CNPq, National Council of Scientific and Technological Development \u2013 Brazil, and by the European-Russian program ORINOCO (FP7-AAT-2010-RTD-Russia; project number 266103).\n\nPublished - CavalieriJordanColoniusEtAl2011.pdf
",
"abstract": "We present experimental results for the acoustic field of jets in the Mach number range 0.35 \u2264 M \u2264 0.6. Data acquired by means of an azimuthal ring of six microphones, whose polar angle, \u03b8, was progressively varied, is decomposed into azimuthal Fourier modes. In agreement with past observations, the sound field for low polar angles (measured with respect to the jet axis) is found to be dominated by the axisymmetric mode, particularly at the peak Strouhal number. As \u03b8 is increased, modes 1 and 2 become increasingly important and dominate at angles greater than \u03b8 \u2248 30\u00b0. A number of features of the axisymmetric mode of the acoustic field suggest that it can be associated with an axially non-compact source, in the form of a convected wave comprising amplification, saturation and decay, and whose axial extension is of the order of several jet diameters: (a) the sound pressure level for peak frequencies is shown be superdirective for all Mach numbers considered, with exponential decay as a function of (1 \u2212 M_c cos \u03b8)^2, in agreement with wavepacket models for an axially non-compact axisymmetric source; (b) while the mode m = 1 spectrum scales with Strouhal number, suggesting that its energy content is associated with turbulence scales, the axisymmetric mode scales with Helmholtz number\u2014the ratio between source length scale and acoustic wavelength; (c) the axisymmetric radiation has a stronger velocity dependence than the higher order azimuthal modes, again in agreement with predictions of the said wave-packet models. We use such a wave-packet model to estimate that the axial extension of the source structure underpinning the axisymmetric component of the sound field is of the order of 6\u20138 jet diameters, and that the source comprises a convected wave with three spatial oscillations, weighted by a Gaussian envelope; such a source structure is in good agreement with past observations based on coherent structure eduction techniques. The present results show that the narrow-band spectrum of the axisymmetric mode contributes to the appearance of the characteristic jet-noise spectrum at low angles, an effect that becomes more marked as the Mach number is increased.",
"date": "2011-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190717-102319217",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190717-102319217",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Conselho Nacional de Desenvolvimento Cient\u00edfico e Tecnol\u00f3gico (CNPq)"
},
{
"agency": "European Research Council (ERC)",
"grant_number": "266103"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2011-2743",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2011-2743",
"primary_object": {
"basename": "CavalieriJordanColoniusEtAl2011.pdf",
"url": "https://authors.library.caltech.edu/records/s1mnq-rnw88/files/CavalieriJordanColoniusEtAl2011.pdf"
},
"resource_type": "conference_item",
"pub_year": "2011",
"author_list": "Cavalieri, Andr\u00e9 V. G.; Jordan, Peter; et el."
},
{
"id": "https://authors.library.caltech.edu/records/938e3-cka41",
"eprint_id": 97188,
"eprint_status": "archive",
"datestamp": "2023-08-19 07:03:33",
"lastmod": "2023-10-20 22:02:21",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Appel\u00f6-D",
"name": {
"family": "Appel\u00f6",
"given": "Daniel"
}
},
{
"id": "Inkman-M",
"name": {
"family": "Inkman",
"given": "Matthew"
}
},
{
"id": "Hagstrom-T",
"name": {
"family": "Hagstrom",
"given": "Thomas"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Hermite Methods for Aeroacoustics: Recent Progress",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 2011 by the author(s). Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 4 Nov 2012. \n\nThis material is based upon work supported, in part, by the National Science Foundation under Grants OCI-0905045 and OCI-0904773 and, in part, by ARO grant W911NF-09-1-0344. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.\n\nPublished - AppeloeInkmanHagstromEtAl2011.pdf
",
"abstract": "We present recent developments on Hermite methods for aeroacoustic simulations including time-stepping methods, hybridization with discontinuous Galerkin methods for handling of boundary conditions and adaptive implementations. By scaling studies reported below we show that the features unique to Hermite methods have promise to enable efficient exploitation of modern petascale architectures. We also present preliminary computations of turbulent jet noise obtained with the current implementation of our compressible Navier-Stokes solver.",
"date": "2011-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190717-102317504",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190717-102317504",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "NSF",
"grant_number": "OCI-0905045"
},
{
"agency": "NSF",
"grant_number": "OCI-0904773"
},
{
"agency": "Army Research Office (ARO)",
"grant_number": "W911NF-09-1-0344"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2011-2757",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2011-2757",
"primary_object": {
"basename": "AppeloeInkmanHagstromEtAl2011.pdf",
"url": "https://authors.library.caltech.edu/records/938e3-cka41/files/AppeloeInkmanHagstromEtAl2011.pdf"
},
"resource_type": "conference_item",
"pub_year": "2011",
"author_list": "Appel\u00f6, Daniel; Inkman, Matthew; et el."
},
{
"id": "https://authors.library.caltech.edu/records/2n6sp-51960",
"eprint_id": 97206,
"eprint_status": "archive",
"datestamp": "2023-08-19 07:03:43",
"lastmod": "2023-10-20 22:03:30",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Br\u00e8s-G-A",
"name": {
"family": "Br\u00e8s",
"given": "Guillaume A."
},
"orcid": "0000-0003-2507-8659"
},
{
"id": "Fares-Ehab",
"name": {
"family": "Fares",
"given": "Ehab"
}
},
{
"id": "Williams-D-R",
"name": {
"family": "Williams",
"given": "David R."
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Numerical Simulations of the Transient Flow Response of a 3D, Low-Aspect-Ratio Wing to Pulsed Actuation",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Fluid Dynamics",
"note": "\u00a9 2011 by G. A. Br\u00e8s, E. Fares, D. R. Williams & T. Colonius. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 14 Jun 2012.\n\nPublished - BresFaresWilliamsEtAl2011.pdf
",
"abstract": "Numerical simulations of the natural and actuated unsteady flow over a three-dimensional low-aspect ratio wing are performed using Lattice Boltzmann method. The LBM simulations match the flow conditions and the detailed wing geometry from previous experiments, including the actuators that are installed internally along the leading edge of the wing. The present study focuses on the transient lift response to short-duration square-wave actuation, for the wing in a uniform flow at five different angles of attack. Overall, both mean and unsteady numerical results show good agreement with the experimental data, in particular at the post-stall angle of attack 19\u00b0, where the maximum lift enhancement occurs. At that angle of attack, the effects of the actuation strength and duration are investigated. In general, the lift response to a single pulse increases with increasing actuator mass-flow rate and pulse duration.",
"date": "2011-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190717-102319521",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190717-102319521",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"other_numbering_system": {
"items": [
{
"id": "2011-3440",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2011-3440",
"primary_object": {
"basename": "BresFaresWilliamsEtAl2011.pdf",
"url": "https://authors.library.caltech.edu/records/2n6sp-51960/files/BresFaresWilliamsEtAl2011.pdf"
},
"resource_type": "conference_item",
"pub_year": "2011",
"author_list": "Br\u00e8s, Guillaume A.; Fares, Ehab; et el."
},
{
"id": "https://authors.library.caltech.edu/records/yy99d-9ep15",
"eprint_id": 97126,
"eprint_status": "archive",
"datestamp": "2023-08-19 07:03:28",
"lastmod": "2023-10-20 21:58:23",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Rodr\u00edguez-D",
"name": {
"family": "Rodr\u00edguez",
"given": "D."
}
},
{
"id": "Samanta-A",
"name": {
"family": "Samanta",
"given": "A."
}
},
{
"id": "Cavalieri-A-V-G",
"name": {
"family": "Cavalieri",
"given": "A. V. G."
},
"orcid": "0000-0003-4283-0232"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "T."
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Jordan-P",
"name": {
"family": "Jordan",
"given": "P."
},
"orcid": "0000-0001-8576-5587"
}
]
},
"title": "Parabolized stability equation models for predicting large-scale mixing noise of turbulent round jets",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 2011 by the author(s). Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 4 Nov 2012. \n\nThis work was supported in part by NAVAIR through an SBIR contract to TTC Technologies, Inc. The technical monitor was Dr. John Spyropoulos. Andr\u00e9 Cavalieri is founded by CNPq, Brazil. The authors would like to thank Dr. Kristjan Gudmundsson, and Drs. Robert Schlinker and Ramons Reba of United Technologies Research Center for their input on this work.\n\nPublished - RodriguezSamantaCavalieriEtAl2011.pdf
",
"abstract": "Parabolized stability equation (PSE) models are being developed to predict the evolution of low-frequency, large-scale wavepacket structures and their radiated sound in highspeed turbulent round jets. Linear PSE wavepacket models were previously shown to be in reasonably good agreement with the amplitude envelope and phase measured using a microphone array placed just outside the jet shear layer. Here we show they also in very good agreement with hot-wire measurements at the jet centerline in the potential core, for a different set of experiments. When used as a model source for acoustic analogy, the predicted far field noise radiation is in reasonably good agreement with microphone measurements for aft angles where contributions from large-scale structures dominate the acoustic field. Nonlinear PSE is then employed in order to determine the relative importance of the mode interactions on the wavepackets. A series of nonlinear computations with randomized initial conditions are use in order to obtain bounds for the evolution of the modes in the natural turbulent jet flow. It was found that nonlinearity has a very limited impact on the evolution of the wavepackets for St \u2265 0.3. Finally, the nonlinear mechanism for the generation of a low-frequency mode as the difference-frequency mode of two forced frequencies is investigated in the scope of the high Reynolds number jets considered in this paper.",
"date": "2011-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190712-112323337",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190712-112323337",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Naval Air Systems Command (NAVAIR)"
},
{
"agency": "Conselho Nacional de Desenvolvimento Cient\u00edfico e Tecnol\u00f3gico (CNPq)"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2011-2838",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2011-2838",
"primary_object": {
"basename": "RodriguezSamantaCavalieriEtAl2011.pdf",
"url": "https://authors.library.caltech.edu/records/yy99d-9ep15/files/RodriguezSamantaCavalieriEtAl2011.pdf"
},
"resource_type": "conference_item",
"pub_year": "2011",
"author_list": "Rodr\u00edguez, D.; Samanta, A.; et el."
},
{
"id": "https://authors.library.caltech.edu/records/zq6nz-fw005",
"eprint_id": 97202,
"eprint_status": "archive",
"datestamp": "2023-08-22 02:29:44",
"lastmod": "2023-10-20 22:03:16",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Coralic-V",
"name": {
"family": "Coralic",
"given": "Vedran"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Numerical simulation of bubble dynamics in deformable vessels",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Cardiovascular system; Computer simulation; Shock waves; Cavitation bubbles; Bubble dynamics; Medical diagnosis",
"note": "\u00a9 2011 Acoustical Society of America. \n\nPublished Online: 08 April 2011. \n\nThis research was supported by the NIH (Grant No. 2PO1DK043881.",
"abstract": "The growth and collapse of cavitation bubbles has been implicated as a potential damage mechanism leading to the rupture of blood vessels in shock wave lithotripsy (SWL) [Bailey et al., in The Fifth International Symposium on Cavitation, Osaka, Japan (2003)]. While this phenomenon has been investigated numerically, the resulting simulations have often assumed some degree of symmetry and have often failed to include a large number of influential physics, such as viscosity, compressibility, surface tension, phase change, and fluid\u2010structure interactions (FSI). We present here our efforts to explore the role that cavitation bubbles play in the rupture of blood vessels in SWL and to improve upon the current state of the numerical approach. We have developed a 3\u2010D, high\u2010order accurate, shock\u2010 and interface\u2010capturing, multicomponent flow algorithm that accounts for the effects of surface tension and FSI. The preliminary results for the case of a bubble collapse, induced by a shock wave lithotripter pulse and occurring inside a deformable vessel, are presented.",
"date": "2011-04-08",
"date_type": "published",
"id_number": "CaltechAUTHORS:20190717-102319126",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190717-102319126",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "NIH",
"grant_number": "2PO1DK043881"
}
]
},
"doi": "10.1121/1.3587690",
"resource_type": "conference_item",
"pub_year": "2011",
"author_list": "Coralic, Vedran and Colonius, Tim"
},
{
"id": "https://authors.library.caltech.edu/records/snj3z-8ba33",
"eprint_id": 97200,
"eprint_status": "archive",
"datestamp": "2023-08-19 05:11:36",
"lastmod": "2023-10-20 22:03:08",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Fedorov-A-V",
"name": {
"family": "Fedorov",
"given": "Alexander V."
}
},
{
"id": "Br\u00e8s-G-A",
"name": {
"family": "Br\u00e8s",
"given": "Guillaume A."
},
"orcid": "0000-0003-2507-8659"
},
{
"id": "Inkman-M",
"name": {
"family": "Inkman",
"given": "Matthew"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Instability of Hypersonic Boundary Layer on a Wall with Resonating Micro-Cavities",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aerospace Systems, Operations and Life Cycle",
"note": "\u00a9 2011 by Alexander V. Fedorov. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 14 Jun 2012. \n\nThis work is supported partially (Fedorov) by the AFOSR/NASA National Center for Hypersonic Research in Laminar-Turbulent Transition. Computer time was provided in part by the Department of Defense High Performance Computing centers.\n\nPublished - FedorovBresInkmanEtAl2011.pdf
",
"abstract": "Ultrasonically absorptive coatings (UAC) can stabilize the Mack second mode and thereby increase the laminar run on configurations where laminar-turbulent transition is second-mode dominated. Theory indicates that the stabilization effect can be essentially enhanced by increasing the UAC porosity. However, direct numerical simulations (DNS) showed that coatings having closely spaced grooves can trigger a new instability whose growth rate can be larger than that of Mack' second mode. The nature of the new instability is investigated theoretically and numerically. 2D linear DNS and stability analysis are performed for the temporally evolving boundary layer on a flat wall at the outer-flow Mach number 6. The wall is covered by UAC comprising equally-spaced spanwise grooves. It is shown that the new mode is associated with acoustic resonances in the grooves. Disturbance fields near mouths of resonating cavities are coupled such that the boundary-layer disturbance is decelerated and becomes unstable. To avoid this detrimental effect the coating should have sufficiently small porosity and/or narrow pores of sufficiently small aspect ratio. Restrictions on these parameters can be estimated using the linear stability theory with the impedance boundary conditions.",
"date": "2011-01",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190717-102318931",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190717-102318931",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Air Force Office of Scientific Research (AFOSR)"
},
{
"agency": "NASA"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2011-373",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2011-373",
"primary_object": {
"basename": "FedorovBresInkmanEtAl2011.pdf",
"url": "https://authors.library.caltech.edu/records/snj3z-8ba33/files/FedorovBresInkmanEtAl2011.pdf"
},
"resource_type": "conference_item",
"pub_year": "2011",
"author_list": "Fedorov, Alexander V.; Br\u00e8s, Guillaume A.; et el."
},
{
"id": "https://authors.library.caltech.edu/records/2y36w-k9688",
"eprint_id": 97191,
"eprint_status": "archive",
"datestamp": "2023-08-19 02:45:28",
"lastmod": "2023-10-20 22:02:35",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Ladeinde-F",
"name": {
"family": "Ladeinde",
"given": "Foluso"
}
},
{
"id": "Alabi-Ken",
"name": {
"family": "Alabi",
"given": "Ken"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Gudmundsson-K",
"name": {
"family": "Gudmundsson",
"given": "Kristjan"
}
},
{
"id": "Schlinker-R-H",
"name": {
"family": "Schlinker",
"given": "Robert H."
}
},
{
"id": "Reba-R-A",
"name": {
"family": "Reba",
"given": "Ramons A."
}
}
]
},
"title": "An Integrated RANS-PSE-Wave Packet Tool for the Prediction of Subsonic and Supersonic Jet Noise",
"ispublished": "unpub",
"full_text_status": "restricted",
"keywords": "Aeroacoustics",
"note": "\u00a9 2010 by TTC Technologies, Inc. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 4 Nov 2012. \n\nThis work is supported by the US Naval Air Command (NAVAIR) Propulsion and Power Division. We would like to acknowledge Drs. James Bridges and Sang Soo Lee for performing the experiments at Glenn. The first author would like to express his appreciation to Dr. Daniel Bodony for the useful discussions on near-field simulation.",
"abstract": "Few engineering tools are suitable for predicting supersonic jet noise, and the development of engine exhaust noise reduction technology for tactical aircraft continues to rely heavily on laboratory scale parametric testing. Aside from intuition and experience with the generally subtle issues involved in low-noise design, there is currently no way to rapidly and cheaply assess whether proposed designs will be effective, and no way to determine whether such designs are optimal. Arguably, this gap in jet noise modeling capability is an impediment toward achieving significant noise reduction for tactical aircraft. The objective of the on-going research program presented in this paper is to develop and demonstrate innovative, highly-efficient computational methodologies for simultaneous nozzle acoustic and aerodynamic design applicable to subsonic and supersonic jet exhaust noise reduction in tactical aircraft. The approach comprises of three major elements: (1) Reynolds-averaged NavierStokes (RANS)-CFD for computing the jet turbulent mean flow, (2) pressure wave packet-based methods for predicting near-field sound generation from the largest scales, based on the Linear Parabolized Stability Equations (LPSE) and the aforementioned RANS solutions, and (3) a method based on the solution of the linear wave equation for determining the acoustic radiation field from the LPSE solution. While these three procedures have received significant attention in the literature, their integration into a single tool for far-field noise prediction has not. To assess the accuracy and robustness of the simulation tool, experimental data has been acquired with near field array directed at detecting changes in the organized turbulence scale structure to link cause (nozzle geometry) and effect (near field and far field noise changes). Both ideally- and non-ideally expanded conditions are being investigated. Forward flight effects have also been measured using an open jet acoustic wind tunnel (at United Technologies Research Center) to evaluate the noise dependence on different operating conditions. The development and preliminary validation of the integrated tool is presented in this paper, with a focus on individual components and their translation into a common format for integration.",
"date": "2010-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190717-102317853",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190717-102317853",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Naval Air Systems Command (NAVAIR)"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2010-4021",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2010-4021",
"resource_type": "conference_item",
"pub_year": "2010",
"author_list": "Ladeinde, Foluso; Alabi, Ken; et el."
},
{
"id": "https://authors.library.caltech.edu/records/ms51t-fc676",
"eprint_id": 97209,
"eprint_status": "archive",
"datestamp": "2023-08-19 02:45:38",
"lastmod": "2023-10-20 22:03:39",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Kerstens-W",
"name": {
"family": "Kerstens",
"given": "Wesley"
}
},
{
"id": "Williams-D",
"name": {
"family": "Williams",
"given": "David"
}
},
{
"id": "Pfeiffer-J",
"name": {
"family": "Pfeiffer",
"given": "Jens"
}
},
{
"id": "King-R",
"name": {
"family": "King",
"given": "Rudibert"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Closed Loop Control of a Wing's Lift for 'Gust' Suppression",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Flow Control",
"note": "\u00a9 2010 by David R. Williams. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 13 Nov 2012. \n\nThe support for this work by the U.S. Air Force Office of Scientific Research MURI (FA9550-05-0369) with program manager Dr. Fariba Fahroo and AFOSR Grant (FA9550-09-1-0189) monitored by Dr. Doug Smith is gratefully appreciated. David Williams gratefully acknowledges partial support from the Alexander von Humboldt foundation. We also acknowledge the partial support from the Illinois NASA Space Grant Consortium for Wesley Kerstens.\n\nSubmitted - WilliamsKerstensPfeifferEtAl2010a.pdf
",
"abstract": "The ability to maintain a constant lift force on a low aspect ratio semi circular wing using pulsed blowing active flow control is experimentally investigated. Dynamic models of the wing's response to pressure (pulsed blowing) actuation and the response to longitudinal gusting are obtained through black-box system identification methods. Robust closed loop controllers are synthesized using a mixed sensitivity loop shaping approach. An additional feedforward disturbance compensation is designed based on a model of the unsteady aerodynamics. The controllers show good suppression of lift fluctuations at low frequencies, but as frequencies increase the control performance degrades due to fundamental physical limitations. The limitations are related to the leading edge vortex formation time.",
"date": "2010-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190717-102319855",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190717-102319855",
"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": "FA9550-05-0369"
},
{
"agency": "Air Force Office of Scientific Research (AFOSR)",
"grant_number": "FA9550-09-1-0189"
},
{
"agency": "Alexander von Humboldt Foundation"
},
{
"agency": "Illinois Space Grant Consortium"
}
]
},
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"id": "2010-4969",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2010-4969",
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"items": [
{
"id": "Br\u00e8s-G-A",
"name": {
"family": "Br\u00e8s",
"given": "Guillaume A."
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{
"id": "Williams-D-R",
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"name": {
"family": "Colonius",
"given": "Tim"
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]
},
"title": "Numerical Simulations of Natural and Actuated Flow over a 3-D, Low-Aspect-Ratio Airfoil",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Fluid Dynamics",
"note": "\u00a9 2010 by G.A. Br\u00e8s, D.R. Williams & T. Colonius. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 13 Nov 2012.\n\nPublished - BresWilliamsColonius2010.pdf
",
"abstract": "Numerical simulations of the unsteady flow over a low-aspect-ratio, low Reynolds number semi-circular planform wing are performed using Lattice Boltzmann method. The simulations exactly match the flow conditions and the detailed geometry from previous wind-tunnel experiments, including the flow actuators installed internally along the leading edge of the wing. To reproduce the pulsed-blowing actuation used in the experiment, a single pulsed square wave forcing is imposed in the simulations as a mass flow boundary condition in the actuators. Three angles of attack, with the active flow control both on and off, are investigated. For both mean and unsteady lift and drag, the numerical simulations show good agreement with the experiments. In particular, the transient increase in lift after the forcing is turned off is well captured in the simulations. Both PIV measurements and transient numerical results indicate that this behavior is associated with the advectionof large vortical structures generated by the flow actuation at the leading edge.",
"date": "2010-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190717-102319343",
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"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
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"items": [
{
"id": "2010-4713",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2010-4713",
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"author_list": "Br\u00e8s, Guillaume A.; Williams, David R.; et el."
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"eprint_id": 97208,
"eprint_status": "archive",
"datestamp": "2023-08-19 01:20:04",
"lastmod": "2023-10-20 22:03:36",
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"creators": {
"items": [
{
"id": "Williams-D",
"name": {
"family": "Williams",
"given": "David"
}
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{
"id": "Kerstens-W",
"name": {
"family": "Kerstens",
"given": "Wesley"
}
},
{
"id": "Buntain-S",
"name": {
"family": "Buntain",
"given": "Seth"
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{
"id": "Quach-V",
"name": {
"family": "Quach",
"given": "Vien"
}
},
{
"id": "Pfeiffer-J",
"name": {
"family": "Pfeiffer",
"given": "Jens"
}
},
{
"id": "King-R",
"name": {
"family": "King",
"given": "Rudibert"
}
},
{
"id": "Tadmor-G",
"name": {
"family": "Tadmor",
"given": "Gilead"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Closed-Loop Control of a Wing in an Unsteady Flow",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aerospace Systems, Operations and Life Cycle",
"note": "\u00a9 2010 by David R. Williams. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 25 Jun 2012. \n\nThe support for this work by the U.S. Air Force Office of Scientific Research MURI (FA9550-05-0369) with program manager Dr. Fariba Fahroo and contract FA9550-09-1-0189 with program manager Dr. Doug Smith is gratefully appreciated. David Williams gratefully acknowledges the partial support of the Alexander von Humboldt foundation. We also acknowledge the support from the Illinois NASA Space Grant Consortium for Wesley Kerstens and Seth Buntain.\n\nSubmitted - WilliamsKerstensPfeifferEtAl2010b.pdf
",
"abstract": "The lift response of the separated flow over a wing to different actuator input disturbances is used to obtain linear models useful for closed-loop control design. The wing has a small aspect ratio, a semi-circular planform, and is fully stalled at a 20\u00b0 angle of attack. Individual pulse-like disturbances and step-input disturbances with randomized frequency were inputs to the actuator, and the lift coefficient increments were output signals. The \"prediction error method\" system identification technique was used to obtain two linear models of the separated flow. A 4th order model reproduced the non-minimum phase behavior of the pulse input, but did not work well for control purposes. The second model identified was limited to first order. The first order model proved to be useful for designing a proportional-integral feedback controller capable of suppressing lift oscillations in unsteady flows. Good suppression of lift oscillations was observed in the experiment after a step change in wind tunnel flow speed occurred. When the control system was tested with a randomized freestream velocity, it reduced the root-mean-square lift oscillation by 50 percent relative to the uncontrolled case.",
"date": "2010-01",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190717-102319753",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190717-102319753",
"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": "FA9550-05-0369"
},
{
"agency": "Air Force Office of Scientific Research (AFOSR)",
"grant_number": "FA9550-09-1-0189"
},
{
"agency": "Alexander von Humboldt Foundation"
},
{
"agency": "NASA"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2010-358",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2010-358",
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"basename": "WilliamsKerstensPfeifferEtAl2010b.pdf",
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"author_list": "Williams, David; Kerstens, Wesley; et el."
},
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"datestamp": "2023-08-19 01:20:09",
"lastmod": "2023-10-20 22:03:49",
"type": "conference_item",
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"creators": {
"items": [
{
"id": "Taira-Kunihiko",
"name": {
"family": "Taira",
"given": "Kunihiko"
},
"orcid": "0000-0002-3762-8075"
},
{
"id": "Rowley-C-W",
"name": {
"family": "Rowley",
"given": "Clarence W."
},
"orcid": "0000-0002-9099-5739"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Feedback Control of High-Lift State for A Low-Aspect-Ratio Wing",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aerospace Systems, Operations and Life Cycle",
"note": "\u00a9 2010 by the authors. Published by the American Institute of Aeronautics and Astronautics, Inc. with permission. \n\nPublished Online: 25 Jun 2012. \n\nThis work was supported by the US Air Force Office of Scientific Research (FA9550-05-1-0369) with the computations made possible by the US Department of Defense HPCMP and the Princeton University TIGRESS programs. Helpful discussions with Prof. David Williams and Mr. Steven Brunton are greatly acknowledged.\n\nSubmitted - TairaRowleyColonius2010.pdf
",
"abstract": "The objective of this study is to employ feedback control to maximize time-average lift on a low-aspect-ratio wing by directly modifying the three-dimensional dynamics of the wake vortices. Flow control around such wing at post-stall angles of attack is numerically investigated at a low Reynolds number of 300 with blowing along the trailing edge. Motivated by the existence of time-periodic high-lift states under open-loop control with periodic excitation, the extremum seeking algorithm is considered for designing feedback control to lock the flow onto such high-lift states. Preliminary results are presented where the close-loop control is able to seek the optimal actuation frequency and yield high lift.",
"date": "2010-01",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190717-102320131",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190717-102320131",
"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": "FA9550-05-1-0369"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2010-357",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2010-357",
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"basename": "TairaRowleyColonius2010.pdf",
"url": "https://authors.library.caltech.edu/records/m7ghj-7ct15/files/TairaRowleyColonius2010.pdf"
},
"resource_type": "conference_item",
"pub_year": "2010",
"author_list": "Taira, Kunihiko; Rowley, Clarence W.; et el."
},
{
"id": "https://authors.library.caltech.edu/records/1bd7n-63c93",
"eprint_id": 97205,
"eprint_status": "archive",
"datestamp": "2023-08-20 01:57:30",
"lastmod": "2023-10-20 22:03:27",
"type": "conference_item",
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"creators": {
"items": [
{
"id": "Br\u00e8s-G-A",
"name": {
"family": "Br\u00e8s",
"given": "Guillaume A."
},
"orcid": "0000-0003-2507-8659"
},
{
"id": "Inkman-M",
"name": {
"family": "Inkman",
"given": "Matthew"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Fedorov-A-V",
"name": {
"family": "Fedorov",
"given": "Alexander V."
}
}
]
},
"title": "Alternate Designs of Ultrasonic Absorptive Coatings for Hypersonic Boundary Layer Control",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Fluid Dynamics",
"note": "\u00a9 2009 by G.A. Bres, M. Inkman, T. Colonius & A. Fedorov. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nThis work is supported by the Air Force of Scientific Research under Grant FA9550-08-1-0251 managed by Dr. John Schmisseur, and partially (Fedorov) by the AFOSR/NASA National Center for Hypersonic Research in Laminar-Turbulent Transition. Computer time was provided in part by the Department of Defense High Performance Computing centers.\n\nPublished - BresInkmanColoniusEtAl2009.pdf
",
"abstract": "Numerical simulations of the linear and nonlinear two-dimensional Navier-Stokes equations are used to parametrically investigate hypersonic boundary layers over ultrasonic absorptive coatings consisting of a uniform array of rectangular pores (slots) with a range of porosities and pore aspect ratios. Based on our previous work, we employ a temporally evolving approximation appropriate to slowly-growing second-mode instabilities. We consider coatings operating in attenuative regimes where the pores are relatively deep and acoustic waves and second mode instabilities are attenuated by viscous effects inside the pores, as well as cancellation/reinforcement regimes with alternating regions of local minima and maxima of the coating acoustic absorption, depending on the frequency of the acoustic waves. The focus is on reinforcement cases which represent a worst case scenario (minimal second-mode damping). For all but one of the cases considered, the linear simulations confirm the results of linear instability theory that employs an approximate porous-wall boundary condition. A particular case with a relatively shallow cavities and very high porosity showed the existence of a shorter wavelength instability that is not predicted by theory. Finally, nonlinear simulations of the same cases led to the same conclusions as linear analysis; in particular, we did not observe any \"tripping\" of the boundary layer by small scale disturbances associated with individual pores.",
"date": "2009-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190717-102319429",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190717-102319429",
"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": "FA9550-08-1-0251"
},
{
"agency": "NASA"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2009-4217",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2009-4217",
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"basename": "BresInkmanColoniusEtAl2009.pdf",
"url": "https://authors.library.caltech.edu/records/1bd7n-63c93/files/BresInkmanColoniusEtAl2009.pdf"
},
"resource_type": "conference_item",
"pub_year": "2009",
"author_list": "Br\u00e8s, Guillaume A.; Inkman, Matthew; et el."
},
{
"id": "https://authors.library.caltech.edu/records/se92k-k1z30",
"eprint_id": 97197,
"eprint_status": "archive",
"datestamp": "2023-08-20 01:57:20",
"lastmod": "2023-10-20 22:02:58",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Joe-Won-Tae",
"name": {
"family": "Joe",
"given": "Won Tae"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "MacMartin-D-G",
"name": {
"family": "MacMynowski",
"given": "Douglas G."
},
"orcid": "0000-0003-1987-9417"
}
]
},
"title": "Optimized Control of Vortex Shedding From an Inclined Flat Plate",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Fluid Dynamics",
"note": "\u00a9 2009 by Won Tae Joe, Tim Colonius, and Douglas G. MacMynowski. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nWork supported by a Multidisciplinary Research Initiative from the United States Air Force Office of Scientific Research (FA9550-05-1-0369, Program Manager: Dr. Fariba Fahroo).\n\nSubmitted - JoeColoniusMacMynowski2009.pdf
",
"abstract": "Optimal control theory is combined with the numerical simulation of an incompressible viscous flow to control vortex shedding in order to maximize lift. A two-dimensional flat plate model is considered at a high angle of attack and a Reynolds number of 300. Actuation is provided by unsteady mass injection near the trailing edge and is modeled by a compact body force. The adjoint of the linearized perturbed equations is solved backwards in time to obtain the gradient of the lift to changes in actuation (the jet velocity), and this information is used to iteratively improve the controls. The optimized control waveform is nearly periodic and locked to vortex shedding. We investigate how features of the optimized waveform modify the vortex shedding and lead to higher lift, and compare the results with sinusoidal open- and closed-loop control from a previous study. In the cases investigated, the optimized control is able to achieve higher average lift than the sinusoidal forcing with lower momentum coefficients. In order to obtain a practically implementable control scheme, the optimized waveform is also implemented in a simple closed-loop controller where the control signal is shifted or deformed periodically to adjust to the (instantaneous) frequency of the lift fluctuations. The feedback utilizes a narrowband filter and an Extended Kalman Filter to robustly estimate the phase of vortex shedding and achieve phase-locked, high lift flow states. Finally, the sensitivity of the flow to the phase shift and other features of the optimized waveform are examined.",
"date": "2009-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190717-102318383",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190717-102318383",
"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": "FA9550-05-1-0369"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2009-4027",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2009-4027",
"primary_object": {
"basename": "JoeColoniusMacMynowski2009.pdf",
"url": "https://authors.library.caltech.edu/records/se92k-k1z30/files/JoeColoniusMacMynowski2009.pdf"
},
"resource_type": "conference_item",
"pub_year": "2009",
"author_list": "Joe, Won Tae; Colonius, Tim; et el."
},
{
"id": "https://authors.library.caltech.edu/records/gbcy2-76j32",
"eprint_id": 97199,
"eprint_status": "archive",
"datestamp": "2023-08-20 01:57:25",
"lastmod": "2023-10-20 22:03:05",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Franck-J-A",
"name": {
"family": "Franck",
"given": "Jennifer"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Oscillatory Control and the Effects of Actuation Frequency on a Wall-Mounted Hump",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Fluid Dynamics",
"note": "\u00a9 2009 by Jennifer Franck and Tim Colonius. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nThis work was supported by a National Science Foundation Graduate Student Fellowship and the US Air Force Office of Scientific Research grant FA9550-05-1-0369.\n\nSubmitted - FranckColonius2009.pdf
",
"abstract": "A large eddy simulation (LES) is used to explore the effects of high frequency actuation on a wall-mounted hump geometry. Low frequency forcing at F^+ ~ O(1) has been shown to increase entrainment through regular shedding of large-scale structures. Using a LES technique previously validated on the baseline and controlled flow over the wall-mounted hump geometry, the effectiveness of high frequency actuation is explored and compared with previous investigations. It is found that the high frequency actuation does not produce distinct vortical structures at the actuation frequency. The resulting mean flow is relatively unaltered by the application of high frequency actuation, although the local flow surrounding the actuation location is slightly modified.",
"date": "2009-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190717-102318572",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190717-102318572",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "NSF Graduate Research Fellowship"
},
{
"agency": "Air Force Office of Scientific Research (AFOSR)",
"grant_number": "FA9550-05-1-0369"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2009-4019",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2009-4019",
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"basename": "FranckColonius2009.pdf",
"url": "https://authors.library.caltech.edu/records/gbcy2-76j32/files/FranckColonius2009.pdf"
},
"resource_type": "conference_item",
"pub_year": "2009",
"author_list": "Franck, Jennifer and Colonius, Tim"
},
{
"id": "https://authors.library.caltech.edu/records/q9w9t-kra38",
"eprint_id": 97189,
"eprint_status": "archive",
"datestamp": "2023-08-20 01:37:45",
"lastmod": "2023-10-20 22:02:25",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Appel\u00f6-D",
"name": {
"family": "Appel\u00f6",
"given": "Daniel"
}
},
{
"id": "Nott-J",
"name": {
"family": "Nott",
"given": "Julian"
}
},
{
"id": "Hall-J",
"name": {
"family": "Hall",
"given": "Jeffrey"
}
}
]
},
"title": "Computational Modeling and Experiments of Natural Convection for a Titan Montgolfiere",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Balloon Systems",
"note": "\u00a9 2009 American Institute of Aeronautics and Astronautics. \n\nPublished Online: 16 Nov 2012.\n\nSubmitted - AppeloColoniusNottEtAl2009.pdf
",
"abstract": "Computational models are developed to predict the natural convection heat transfer and buoyancy for a Montgolfiere under conditions relevant to the Titan atmosphere. Idealized single and double-walled balloon geometries are simulated using algorithms suitable for both laminar and (averaged) turbulent convection. Steady-state performance results are compared to existing heat transfer coefficient correlations. The laminar results, in particular, are used to test the validity of the correlations in the absence of uncertainties associated with turbulence modeling. Some discrepancies are observed, especially for convection in the gap, and appear to be primarily associated with temperature nonuniformity on the balloon surface. The predicted buoyancy for the single-walled balloon in the turbulent convection regime, predicted with a standard k \u2212 \u03b5 turbulence model, was within 10% of predictions based on the empirical correlations. There was also good agreement with recently conducted experiments in a cryogenic facility designed to simulate the Titan atmosphere.",
"date": "2009-05",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
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"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
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"author_list": "Colonius, Tim; Appel\u00f6, Daniel; et el."
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"id": "Gudmundsson-K",
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},
"title": "Parabolized Stability Equation Models for Turbulent Jets and Their Radiated Sound",
"ispublished": "unpub",
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"keywords": "Aeroacoustics",
"note": "\u00a9 2009 by Kristjan Gudmundsson and Tim Colonius. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 4 Nov 2012. \n\nThis work was supported by NAVAIR/TTC Technologies. We would like to express great appreciation to Dr. James Bridges and colleagues at the NASA Glenn Research Center for providing us with their data, as well as to Dr. Takao Suzuki for help with data processing.\n\nPublished - GuhmundssonColonius2009.pdf
",
"abstract": "In this paper we present several refinements to a wave-packet model of sound generation from large-scale turbulence. We examine heated and unheated jets at Mach numbers of 0.5 and 0.9. Pressure fluctuations associated with large-scale structures are modeled with the Parabolized Stability Equations (PSE) for linear disturbances to the turbulent mean-flow. We show that PSE provides better agreement with near-field microphone-array data at low frequencies than previous models based on linear stability theory. We examine the extent to which microphone data is contaminated by fluctuations uncorrelated with largescale structures. By filtering out the uncorrelated fluctuations, via the proper orthogonal decomposition (POD), better agreement between data and theory is obtained.",
"date": "2009-05",
"date_type": "published",
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"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Naval Air Systems Command (NAVAIR)"
},
{
"agency": "TTC Technologies"
}
]
},
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{
"id": "Schlinker-R-H",
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"family": "Schlinker",
"given": "R. H."
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"id": "Simonich-J-C",
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"family": "Simonich",
"given": "J. C."
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"title": "Supersonic Jet Noise from Round and Chevron Nozzles: Experimental Studies",
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"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 2009 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. \n\nPublished Online: 4 Nov 2012. \n\nThe authors gratefully acknowledge NAVAIR and TTC Technologies Inc. for supporting this effort.\n\nPublished - SchlinkerSimonichShannonEtAl2009.pdf
",
"abstract": "High speed exhaust noise reduction continues to be a research challenge for supersonic cruise business jets as well as for current and future tactical military aircraft. Significant noise reduction may be possible from advanced concepts for controlling instability generated large-scale turbulence structures in the jet shear layer, generally accepted to be the source of aft-angle noise. In response to this opportunity, our team is focused on experimental diagnostic studies and unique instability modeling suited for identifying control strategies to reduce large scale structure noise. The current paper benchmarks the jet noise from supersonic nozzles designed to provide the supporting experimental data and validation of the modeling. Laboratory scale jet noise experiments are presented for a Mach number of Mj = 1.5 with stagnation temperature ratios ranging from Tr = 0.75 to 2. The baseline configuration is represented by a round converging-diverging (CD) ideal expansion nozzle. A round CD nozzle with chevrons is included as the first of several planned non-circular geometries directed at demonstrating the impact on large scale structure noise and validating noise prediction methods for geometries of future technological interest. Overexpanded and underexpanded conditions were tested on both nozzle configurations. The resulting data base provides an opportunity to benchmark the statistical characteristics of round and chevron nozzle data. The current paper examines far field spectra, directivity patterns, and overall sound pressure level dependence comparing observed characteristics with the fine scale turbulence noise and large-scale turbulence structure noise characteristics identified by Tam. In addition, the paper probes the effect of chevrons on the developing flow field and suppression of screech tones. Measurements are also reported from a far-field narrow aperture phased array system used to map the acoustic source distribution on the jet axis. The dominant source region, situated between the end of the potential core and the sonic point, was found to agree with the peak amplitude location of the jet near field wavepackets measured using a unique near field array. This observation supports the cause-effect link between large-scale turbulence structures in the shear layer and their dominant contribution to aft radiated far field noise.",
"date": "2009-05",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190717-102320667",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190717-102320667",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Naval Air Systems Command (NAVAIR)"
},
{
"agency": "TTC Technologies"
}
]
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{
"id": "Krimmel-J",
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"family": "Krimmel",
"given": "Jeffrey"
}
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},
"title": "In vivo simulation of shock wave lithotripsy: Wave focusing in inhomogeneous materials",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Multiphase flows; Piezoelectricity; Wave propagation; Shock waves; Speed of sound; Adaptive mesh refinement; Medical diagnosis",
"note": "\u00a9 2009 Acoustical Society of America. \n\nPublished Online: 08 April 2009.",
"abstract": "Shock wave generation and focusing in electrohydraulic, electromagnetic, and piezoelectric lithotripters are simulated numerically. Inhomogeneities associated with wave propagation in vivo are modeled using data from The Visible Human Project. The approximate time\u2010domain relaxation model of Yang and Cleveland (2005) was used to simulate attenuation and dispersion in the tissuelike media. The simulations utilize a MUSCL\u2010type shock capturing scheme with adaptive mesh refinement (AMR). In vitro focal region pressure measurements compare favorably with available experimental data for each lithotripter type. Preliminary in vivo simulation results show significant dispersion associated with the nonuniform sound speed, including increases of up to 50% in focal pressure amplitudes and the presence of multiple pressure minima/maxima in the focal waveform. We will also discuss the extension of the AMR framework to account for cavitation via a previously developed ensemble\u2010averaged continuous two\u2010phase flow model.",
"date": "2009-04-09",
"date_type": "published",
"id_number": "CaltechAUTHORS:20190717-102318035",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190717-102318035",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"doi": "10.1121/1.4783996",
"resource_type": "conference_item",
"pub_year": "2009",
"author_list": "Krimmel, Jeffrey and Colonius, Tim"
},
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"id": "https://authors.library.caltech.edu/records/pxaz0-anz31",
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"datestamp": "2023-08-20 00:38:06",
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{
"id": "Williams-D",
"name": {
"family": "Williams",
"given": "David"
}
},
{
"id": "Quach-V",
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"family": "Quach",
"given": "Vien"
}
},
{
"id": "Kerstens-W",
"name": {
"family": "Kerstens",
"given": "Wesley"
}
},
{
"id": "Buntain-S",
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"family": "Buntain",
"given": "Seth"
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{
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}
},
{
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},
"title": "Low Reynolds Number Wing Response to an Oscillating Freestream With and Without Feed Forward Control",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aerospace Systems, Operations and Life Cycle",
"note": "\u00a9 2009 by David R. Williams. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 15 Jun 2012. \n\nThe support for this work by the U.S. Air Force Office of Scientific Research MURI (FA9550-05-0369) with program manager Dr. Fariba Fahroo is gratefully appreciated. We also acknowledge the support from the Illinois NASA Space Grant Consortium for Wes Kerstens.\n\nPublished - WilliamsQuachKerstensEtAl2009.pdf
",
"abstract": "The unsteady lift of a low Reynolds number wing in an oscillating freestream is documented in terms of its amplitude and phase. The phase variation of the lift relative to the freestream velocity shows a larger phase difference than predicted by classical unsteady flow theory. A constant time delay between the lift and the actuator was observed to be \u03c4^+ = t_(delay)U/c = 5.3 when normalized by the freestream speed and chord. Feed forward control of pulsed-jet actuators is used to modulate the lift coefficient of the wing, in an attempt to suppress the lift oscillations. Suppression of the fluctuating lift at the fundamental frequency was partially successful, but additional \"noise\" was added to harmonics of the lift signal by the controller.",
"date": "2009-01",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190717-102319638",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190717-102319638",
"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": "FA9550-05-0369"
},
{
"agency": "NASA"
}
]
},
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"author_list": "Williams, David; Quach, Vien; et el."
},
{
"id": "https://authors.library.caltech.edu/records/nw5da-r9t24",
"eprint_id": 97214,
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"datestamp": "2023-08-20 00:38:12",
"lastmod": "2023-10-20 22:03:53",
"type": "conference_item",
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"creators": {
"items": [
{
"id": "Taira-Kunihiko",
"name": {
"family": "Taira",
"given": "Kunihiko"
},
"orcid": "0000-0002-3762-8075"
},
{
"id": "Colonius-T",
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"family": "Colonius",
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},
"title": "On the Effect of Tip Vortices in Low-Reynolds-Number Post-Stall Flow Control",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aerospace Systems, Operations and Life Cycle",
"note": "\u00a9 2009 by the authors. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 15 Jun 2012. \n\nThis work was supported by the US Air Force Office of Scientific Research (FA9550-05-1-0369) with some of the computations made possible by the US Department of Defense High Performance Computing Modernization Program. We are thankful to Professors Clarence W. Rowley, Morteza Gharib, David R. Williams, Gilead Tadmor, and Dr. William B. Dickson for the enlightening discussions.\n\nPublished - TairaColonius2009b.pdf
",
"abstract": "We numerically investigate the application of steady blowing to three-dimensional stalled flows around low-aspect-ratio rectangular flat-plate wings at a Reynolds number of 300. The objective of this study is to explore techniques to enhance lift by directly modifying the dynamics of the wake vortices. Out of various combinations of forcing location and direction considered, we identify two configurations that provide significant lift enhancement. In these cases, actuation appears to strengthen the tip vortices for increased downward induced velocity upon the leading-edge vortices. This in turn moves the low-pressure core directly above the top surface of the wing to greatly enhance lift.",
"date": "2009-01",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190717-102320309",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190717-102320309",
"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": "FA9550-05-1-0369"
}
]
},
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{
"id": "2009-376",
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{
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"creators": {
"items": [
{
"id": "Rowley-C-W",
"name": {
"family": "Rowley",
"given": "Clarence W."
},
"orcid": "0000-0002-9099-5739"
},
{
"id": "Ahuja-Sunil",
"name": {
"family": "Ahuja",
"given": "Sunil"
}
},
{
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"given": "Kunihiko"
},
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{
"id": "Colonius-T",
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"family": "Colonius",
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]
},
"title": "Closed-Loop Control of Leading Edge Vorticity on a 3D Wing: Simulations and Low-Dimensional Models",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Fluid Dynamics",
"note": "\u00a9 2008 by the authors. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 15 Jun 2012. \n\nThis work was supported by the AFOSR, grant FA9550-05-1-0369, with program manager Dr. Fariba Fahroo. We gratefully acknowledge Prof. Yannis Kevrekidis for helpful advice about many aspects of this work, especially the selective frequency damping.\n\nPublished - RowleyAhujaTairaEtAl2008.pdf
",
"abstract": "We study model-based feedback control of the low-Reynolds-number flow over a flat plate at large angles of attack, in both two and three dimensions. Our long-term goal is to be able to manipulate the leading-edge vortices that form on low-aspect-ratio wings at high angles of attack, and that often contribute to exceptionally large lift coefficients. Intwo-dimensional simulations, we present a model-based feedback controller that uses an observer to reconstruct the entire flow field from velocity measurements at three locations, and stabilizes the flow at an angle of attack for which the natural flow state is periodic shedding. In three-dimensional simulations, we use open-loop forcing to study actuator placement, and conclude that trailing-edge actuation is more effective than leading-edge actuation in influencing the forces on the plate, as well as the wake structures. Finally, we present initial results towards extending our model-based control design to the 3D setting, and apply a selective frequency damping method to find unstable equilibrium flow fields in 3D simulations.",
"date": "2008-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190717-102320932",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190717-102320932",
"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": "FA9550-05-1-0369"
}
]
},
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{
"id": "2008-3981",
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}
]
},
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"pub_year": "2008",
"author_list": "Rowley, Clarence W.; Ahuja, Sunil; et el."
},
{
"id": "https://authors.library.caltech.edu/records/6h8ep-hra38",
"eprint_id": 97215,
"eprint_status": "archive",
"datestamp": "2023-08-19 22:52:36",
"lastmod": "2023-10-20 22:03:57",
"type": "conference_item",
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"creators": {
"items": [
{
"id": "Tadmor-G",
"name": {
"family": "Tadmor",
"given": "Gilead"
}
},
{
"id": "Williams-D-R",
"name": {
"family": "Williams",
"given": "David R."
}
},
{
"id": "Collins-Jesse",
"name": {
"family": "Collins",
"given": "Jesse"
}
},
{
"id": "Colonius-T",
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{
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"name": {
"family": "Rowley",
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}
]
},
"title": "Control of a Semi-Circular Planform Wing in a \"Gusting\" Unsteady Free Stream Flow II: Modeling and Feedback Design",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Fluid Dynamics",
"note": "\u00a9 2008 by David Williams. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 15 Jun 2012. \n\nWe gratefully acknowledge the support for this work by the U.S. Air Force Office of Scientific Research (FA9550-05-0369 and FA9550-06-1-0373) with program manager Dr. Fariba Fahroo.\n\nPublished - TadmorWilliamsCollinsEtAl2008.pdf
",
"abstract": "Active flow control has been demonstrated in Part I of this article to modify the lift, drag and pitching moments on a semi-circular wing during \"gusting\" flow conditions. The low aspect ratio wing, AR = 2.54, is mounted on a captive trajectory system that responds to the instantaneous lift force and pitching moment and the \"gusting\" flow is simulated by a 0.2 Hz oscillation of the free stream speed of the wind tunnel. The mean chord Reynolds number of the wing is 70,600. Active flow control occurs along the leading edge of the airfoil, which contains 16 spatially localized micro-valve actuators. Details of the experimental setup, a quasi steady state lift model and results involving open-loop proof of concept validation are provided in Part I of this paper. Here we outline principles and considerations associated with close loop design that will be discussed in our talk.",
"date": "2008-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190717-102320405",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190717-102320405",
"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": "FA9550-05-0369"
},
{
"agency": "Air Force Office of Scientific Research (AFOSR)",
"grant_number": "FA9550-06-1-0373"
}
]
},
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"id": "2008-3977",
"name": "AIAA Paper"
}
]
},
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"pub_year": "2008",
"author_list": "Tadmor, Gilead; Williams, David R.; et el."
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{
"id": "https://authors.library.caltech.edu/records/qw3ea-1hn26",
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"items": [
{
"id": "Williams-D-R",
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{
"id": "Tadmor-G",
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"family": "Tadmor",
"given": "Gilead"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Control of a Semi-Circular Planform Wing in a \"Gusting\" Unsteady Freestream Flow: I - Experimental Issues",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Fluid Dynamics",
"note": "\u00a9 2008 by David R. Williams. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 15 Jun 2012. \n\nThe support for this work by the U.S. Air Force Office of Scientific Research MURI (FA9550-05-0369) with program manager Dr. Fariba Fahroo is gratefully appreciated. We also acknowledge the support from the Illinois NASA Space Grant Consortium for partial support of Jesse Collins.\n\nPublished - WilliamsCollinsTadmorEtAl2008.pdf
",
"abstract": "Active flow control is used to modify the lift, drag and pitching moments on a semicircular wing during \"gusting\" flow conditions. A longitudinal oscillating flow component has an amplitude of 10 percent of the freestream speed and a frequency giving k = 0.048 (f = 0.2 Hz). The aspect ratio of the wing is AR = 2.54, and the chord Reynolds number of the wing is 70,600. Pulsed-blowing flow control actuation occurs along the leading edge of the airfoil via 16 spatially localized micro-valve actuators. Feed-forward control based on a quasi-steady lift model is used to stabilize lift fluctuations generated by an oscillating free stream, which simulates the longitudinal component of a gusting flow. The quasi-steady system model reduces the amplitude of the fundamental and first harmonics of lift oscillations, but does not account for time delays. The time delay between the lift and the freestream oscillation was measured to be \u03c4_(u)^(+) = 4.8. The time delay between the lift and the actuator input signal was found to be \u03c4_(a)^(+) = 11.3.",
"date": "2008-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190717-102319947",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190717-102319947",
"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": "FA9550-05-0369"
},
{
"agency": "NASA"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2008-3976",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2008-3976",
"primary_object": {
"basename": "WilliamsCollinsTadmorEtAl2008.pdf",
"url": "https://authors.library.caltech.edu/records/qw3ea-1hn26/files/WilliamsCollinsTadmorEtAl2008.pdf"
},
"resource_type": "conference_item",
"pub_year": "2008",
"author_list": "Williams, David R.; Collins, Jesse; et el."
},
{
"id": "https://authors.library.caltech.edu/records/gzafe-1pf52",
"eprint_id": 97217,
"eprint_status": "archive",
"datestamp": "2023-08-19 22:52:46",
"lastmod": "2023-10-20 22:04:04",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Tadmor-G",
"name": {
"family": "Tadmor",
"given": "Gilead"
}
},
{
"id": "Bissex-Daniel",
"name": {
"family": "Bissex",
"given": "Daniel"
}
},
{
"id": "Noack-Bernd-R",
"name": {
"family": "Noack",
"given": "Bernd R."
}
},
{
"id": "Morzy\u0144ski-Marek",
"name": {
"family": "Morzy\u0144ski",
"given": "Marek"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Taira-Kunihiko",
"name": {
"family": "Taira",
"given": "Kunihiko"
},
"orcid": "0000-0002-3762-8075"
}
]
},
"title": "Fast Approximated POD for a Flat Plate Benchmark with a Time Varying Angle of Attack",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Flow Control",
"note": "\u00a9 2008 by Gilead Tadmor. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 15 Jun 2012. \n\nWe gratefully acknowledge the support for this work by the U.S. Air Force Office of Scientific Research (FA9550-05-0369 and FA9550-06-1-0373) with program manager Dr. Fariba Fahroo.\n\nSubmitted - TadmorBissexNoackEtAl2008a.pdf
",
"abstract": "An approximate POD algorithm provides an empirical Galerkin approximation with guaranteed a priori lower bound on the required resolution. The snapshot ensemble is partitioned into several sub-ensembles. Cross correlations between these sub-ensembles are approximated in terms of a far smaller correlation matrix. Computational speedup is nearly linear in the number of partitions, up to a saturation that can be estimated a priori. The algorithm is particularly suitable for analyzing long transient trajectories of high dimensional simulations, but can be applied also for spatial partitioning and parallel processing of very high spatial dimension data. The algorithm is demonstrated using transient data from two simulations. First, a two dimensional simulation of the flow over a flat plate, as it transitions from AOA = 30\u00b0 to a horizontal position and back. Second, a three dimensional simulation of a flat plate with aspect ratio two as it transitions from a horizontal position to AOA = 30\u00b0.",
"date": "2008-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190717-102320576",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190717-102320576",
"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": "FA9550-05-0369"
},
{
"agency": "Air Force Office of Scientific Research (AFOSR)",
"grant_number": "FA9550-06-1-0373"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2008-4191",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2008-4191",
"primary_object": {
"basename": "TadmorBissexNoackEtAl2008a.pdf",
"url": "https://authors.library.caltech.edu/records/gzafe-1pf52/files/TadmorBissexNoackEtAl2008a.pdf"
},
"resource_type": "conference_item",
"pub_year": "2008",
"author_list": "Tadmor, Gilead; Bissex, Daniel; et el."
},
{
"id": "https://authors.library.caltech.edu/records/ay8fn-69b90",
"eprint_id": 97258,
"eprint_status": "archive",
"datestamp": "2023-08-19 22:53:00",
"lastmod": "2023-10-20 22:07:03",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Br\u00e8s-G-A",
"name": {
"family": "Br\u00e8s",
"given": "Guillaume A."
},
"orcid": "0000-0003-2507-8659"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Fedorov-A-V",
"name": {
"family": "Fedorov",
"given": "Alexander V."
}
}
]
},
"title": "Interaction of Acoustic Disturbances with Micro-Cavities for Ultrasonic Absorptive Coatings",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Theoretical Fluid Mechanics",
"note": "\u00a9 2008 by G. A. Bres, T. Colonius & A. V. Fedorov. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 14 Jun 2012. \n\nThe authors would like to acknowledge contributions to this work by Dr. Norm Malmuth, whose passionate work on diverse topics, including UAC, and generosity to his collaborators will be sorely missed. This work was supported by the Air Force of Scientific Research under Contract FA9550-06-C-0097.\n\nPublished - BresColoniusFedorov2008.pdf
",
"abstract": "Numerical simulations are performed to investigate the interaction of acoustic waves with an array of equally-spaced two-dimensional micro-cavities on an otherwise flat plate without external boundary-layer flow. This acoustic scattering problem is important in the design of ultrasonic absorptive coatings (UAC) for hypersonic laminar flow control. The reflection coefficient, characterizing the ratio of the reflected wave amplitude to the incident wave amplitude, is computed as a function of the acoustic wave frequency and angle of incidence, for coatings of different porosity, at various acoustic Reynolds numbers relevant to hypersonic flight. Overall, the numerical results validate predictions from existing theoretical modeling. In general, the amplitude of the reflection coefficient has local minima at some specific frequencies. A simple model to predict these frequencies is presented. The simulations also highlight the presence of resonant acoustic modes caused by coupling of small-scale scattered waves near the UAC surface. Finally, the cavity depth and the porosity are identified as the most important parameters for UAC design. Guidelines for the choice of these parameters are suggested.",
"date": "2008-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190718-165126161",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190718-165126161",
"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": "FA9550-06-C-0097"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2008-3903",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2008-3903",
"primary_object": {
"basename": "BresColoniusFedorov2008.pdf",
"url": "https://authors.library.caltech.edu/records/ay8fn-69b90/files/BresColoniusFedorov2008.pdf"
},
"resource_type": "conference_item",
"pub_year": "2008",
"author_list": "Br\u00e8s, Guillaume A.; Colonius, Tim; et el."
},
{
"id": "https://authors.library.caltech.edu/records/fpvvg-zzx85",
"eprint_id": 97257,
"eprint_status": "archive",
"datestamp": "2023-08-19 22:52:55",
"lastmod": "2023-10-20 22:06:59",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Br\u00e8s-G-A",
"name": {
"family": "Br\u00e8s",
"given": "Guillaume A."
},
"orcid": "0000-0003-2507-8659"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Fedorov-A-V",
"name": {
"family": "Fedorov",
"given": "Alexander V."
}
}
]
},
"title": "Stability of Temporally Evolving Supersonic Boundary Layers over Micro-Cavities for Ultrasonic Absorptive Coatings",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Theoretical Fluid Mechanics",
"note": "\u00a9 2008 by G. A. Bres, T. Colonius, & A. V. Federov. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 14 Jun 2012. \n\nThe authors would like to acknowledge contributions to this work by Norm Malmuth, whose passionate work on diverse topics, including UAC, and generosity to his collaborators will be sorely missed. This work was supported by the Air Force of Scientific Research under Contract FA9550-06-C-0097.\n\nSubmitted - BresColoniusFedorov2008a.pdf
",
"abstract": "Ultrasonic absorptive coatings, consisting of regularly-spaced arrays of micro-cavities, have previously been shown to effectively damp second-mode instability for the purpose of delaying transition in hypersonic boundary layers. However, previous simulations and stability analysis have used approximate porous-wall boundary conditions. Here we investigate the feasibility of using direct numerical simulation to directly compute the hypersonic boundary layer including the micro-cavities. In order to keep the problem computationally tractable, we restrict our attention to the two-dimensional case (which is relevant since the second-mode is initially two dimensional), and we show that temporally evolving layers display qualitatively similar behavior to spatially developing boundary layer and instabilities. We validate the numerical method by comparing the simulation results to temporal linear stability analysis of the (frozen) velocity and temperature profiles from the direct numerical simulation. Two-dimensional linear simulations of the boundary layer on a flat plate and over a porous coating are performed, and it is shown that the presence of the cavities attenuates the instability waves, as expected from theory.",
"date": "2008-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190718-165126067",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190718-165126067",
"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": "FA9550-06-C-0097"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2008-4337",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2008-4337",
"primary_object": {
"basename": "BresColoniusFedorov2008a.pdf",
"url": "https://authors.library.caltech.edu/records/fpvvg-zzx85/files/BresColoniusFedorov2008a.pdf"
},
"resource_type": "conference_item",
"pub_year": "2008",
"author_list": "Br\u00e8s, Guillaume A.; Colonius, Tim; et el."
},
{
"id": "https://authors.library.caltech.edu/records/x6sqk-8vq79",
"eprint_id": 97216,
"eprint_status": "archive",
"datestamp": "2023-08-19 22:52:41",
"lastmod": "2023-10-20 22:04:00",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Tadmor-G",
"name": {
"family": "Tadmor",
"given": "Gilead"
}
},
{
"id": "Bissex-Daniel",
"name": {
"family": "Bissex",
"given": "Daniel"
}
},
{
"id": "Noack-Bernd-R",
"name": {
"family": "Noack",
"given": "Bernd R."
}
},
{
"id": "Morzy\u0144ski-Marek",
"name": {
"family": "Morzy\u0144ski",
"given": "Marek"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Taira-Kunihiko",
"name": {
"family": "Taira",
"given": "Kunihiko"
},
"orcid": "0000-0002-3762-8075"
}
]
},
"title": "Temporal-Harmonic Specific POD Mode Extraction",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Flow Control",
"note": "\u00a9 2008 by Gilead Tadmor. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 15 Jun 2012.\n\nSubmitted - TadmorBissexNoackEtAl2008.pdf
",
"abstract": "While POD / PCA / KL approximations are statistically energetically optimal, statistical optimality is indeed the sole consideration these (equivalent) methods invoke. This type of approximation is neither geared for, nor is it optimized to extract modes based on their significance to an underlying system dynamics. Furthermore, as computational considerations limit the size of empirical ensembles used for mode extraction, the resulting mode set is significantly effected by the arbitrariness of the ensemble selection. System theoretic model reductions methods aim to home on dynamically significant modes by direct interrogation of the underlying equation, such as the linearized Navier-Stokes equations. An alternative / complimentary approach is to impose a priori knowledge of structural properties, such as symmetry and periodicity, on the mode-extraction procedure. The idea is that these conditions will force the selection of physically meaningful modes, and thus enables an effective appeal to first principles. Here we focus on systems known to be periodically dominant, and describe a simple method to extract modes associated with temporal harmonics. The method accommodates time variations in the dominant frequency(ies) and exploits a preliminary data compression, such as by the standard POD procedure.",
"date": "2008-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190717-102320488",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190717-102320488",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"other_numbering_system": {
"items": [
{
"id": "4190",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2008-4190",
"primary_object": {
"basename": "TadmorBissexNoackEtAl2008.pdf",
"url": "https://authors.library.caltech.edu/records/x6sqk-8vq79/files/TadmorBissexNoackEtAl2008.pdf"
},
"resource_type": "conference_item",
"pub_year": "2008",
"author_list": "Tadmor, Gilead; Bissex, Daniel; et el."
},
{
"id": "https://authors.library.caltech.edu/records/v9x61-yz433",
"eprint_id": 97195,
"eprint_status": "archive",
"datestamp": "2023-08-22 11:44:14",
"lastmod": "2023-10-20 22:02:51",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Johnsen-E",
"name": {
"family": "Johnsen",
"given": "Eric"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Damage potential of single\u2010bubble collapse in shockwave lithotripsy",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Organs; Wave propagation; Shock waves; Medical diagnosis",
"note": "\u00a9 2009 Acoustical Society of America. \n\nPublished Online: 09 May 2008. \n\nThis work is supported by NIH grant PO1 DK043881 and ONR Grant N00014\u201006\u20101\u20100730.",
"abstract": "In shockwave lithotripsy, the combined effect of focused shockwaves and cavitation pulverizes kidney stones. Although cavitation is known to play an important role in stone comminution, the underlying mechanism is not fully understood. The goal of the present study is to quantify the potential damage caused by Rayleigh collapse (RC) and shock\u2010induced collapse (SIC) of a single bubble near a stone. A high\u2010order accurate, quasi\u2010conservative, shock\u2010 and interface\u2010capturing scheme [E. Johnsen and T. Colonius, J. Comput. Phys. 2006] is employed to simulate both phenomena. A high\u2010speed re\u2010entrant jet forms during the collapse and hits the distal side of the bubble, thereby generating a water\u2010hammer pressure wave. A high pressure is measured along the stone surface upon the impact of this wave, thus providing potential for erosion. In SIC, this pressure may reach 1 GPa and bubbles within approximately 15 initial radii generate a pressure higher than the incoming pulse. In addition, by using the present results as time\u2010dependent boundary conditions for an elastic wave propagation code, it is shown that a tension large enough to lead to failure may be achieved within small stones or fragments.",
"date": "2008-05-09",
"date_type": "published",
"id_number": "CaltechAUTHORS:20190717-102318220",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190717-102318220",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "NIH",
"grant_number": "PO1 DK043881"
},
{
"agency": "Office of Naval Research (ONR)",
"grant_number": "N00014\u201006\u20101\u20100730"
}
]
},
"doi": "10.1121/1.2933980",
"resource_type": "conference_item",
"pub_year": "2008",
"author_list": "Johnsen, Eric and Colonius, Tim"
},
{
"id": "https://authors.library.caltech.edu/records/adbbn-2va10",
"eprint_id": 97192,
"eprint_status": "archive",
"datestamp": "2023-08-22 11:44:10",
"lastmod": "2023-10-20 22:02:41",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Krimmel-J",
"name": {
"family": "Krimmel",
"given": "Jeffrey"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Numerical simulation of shock wave generation and focusing in shock wave lithotripsy",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Computer simulation; Bubble model; Bubble dynamics; Fluid dynamics; Vector fields; Organs; Piezoelectricity; Shock waves; Lenses; Medical diagnosis",
"note": "\u00a9 2008 Journal of the Acoustical Society of America. \n\nPublished Online: 09 May 2008. \n\nThis work is supported by NIH grant PO1 DK043881 and ONR Grant N00014\u201006\u20101\u20100730.",
"abstract": "Shock wave lithotripsy is a procedure where focused shock waves are fired at kidney stones in order to pulverize them. Lithotripters with different source mechanisms and reflector shapes (or lenses) are in clinical use, but prediction of focal region pressure is made difficult by nonlinearity and cavitation. We report on development of a numerical simulation framework aimed at accurate prediction of focal region pressures and bubble dynamics. Shock wave generation and beam focusing are simulated via the Euler equations with MUSCL\u2010type shock\u2010capturing scheme and adaptive mesh refinement (AMR). Electrohydraulic, electromagnetic, and piezoelectric\u2010array lithotripters are modeled with axisymmetric geometries. In the electrohydraulic case, an expanding bubble model simulates spark firing. In the piezoelectric case, a boundary condition prescribing the motion of individual elements is used. Calculated peak pressures and pulse widths agree well with experimental data for the electrohydraulic and electromagnetic lithotripters. For the piezoelectric case, peak pressures are increasingly over\u2010predicted by the model when more elements are fired, and reasons for this discrepancy will be discussed. Finally, we compare the spatial and temporal characteristics of the focal pressure fields for several clinical lithotripters in the context of observed stone comminution efficacy and tissue damage.",
"date": "2008-05-09",
"date_type": "published",
"id_number": "CaltechAUTHORS:20190717-102317947",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190717-102317947",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "NIH",
"grant_number": "PO1 DK043881"
},
{
"agency": "Office of Naval Research (ONR)",
"grant_number": "N00014\u201006\u20101\u20100730"
}
]
},
"doi": "10.1121/1.2933977",
"resource_type": "conference_item",
"pub_year": "2008",
"author_list": "Krimmel, Jeffrey and Colonius, Tim"
},
{
"id": "https://authors.library.caltech.edu/records/7anqp-90624",
"eprint_id": 97219,
"eprint_status": "archive",
"datestamp": "2023-08-19 22:40:37",
"lastmod": "2023-10-20 22:04:11",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Schlinker-R-H",
"name": {
"family": "Schlinker",
"given": "R. H."
}
},
{
"id": "Simonich-J-C",
"name": {
"family": "Simonich",
"given": "J. C."
}
},
{
"id": "Reba-R-A",
"name": {
"family": "Reba",
"given": "R. A."
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "T."
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Ladeinde-F",
"name": {
"family": "Ladeinde",
"given": "F."
}
}
]
},
"title": "Decomposition of High Speed Jet Noise: Source Characteristics and Propagation Effects",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 2008 by Robert H. Schlinker. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 4 Nov 2012. \n\nThe authors gratefully acknowledge the support of NAVAIR and TTC Technologies Inc., the SBIR partner in this work.\n\nPublished - SchlinkerSimonichRebaEtAl2008.pdf
",
"abstract": "Current research programs directed at supersonic engine exhaust noise reduction are demonstrating benefits of 3-4 dBA using passive methods to increase jet mixing and break up shock cells in over-expanded flows. While progress is being made, high speed jet noise continues to be a research challenge for small business jets and tactical military aircraft. The current work benchmarks high speed jet noise using laboratory scale jets for the purpose of a) identifying source and propagation mechanisms, and b) providing validation data for simulation/modeling methods. Laboratory scale experiments are presented over a Mach number range of M = 0.68 to 1.5 with static temperature ratio ranging from Tr = 0.68 to 2. A unique near field rotating phased microphone array technique was used to identify the large-scale turbulence structure noise source and Mach waves in supersonic shock-free jets. A companion paper documents the near field pressure statistics and projection of the convected wave packet to the far field. Validation against the directly measured far field levels quantitatively establishes the large scale structure noise contributions. The combined studies underpin a long term effort to develop modeling methods and new concepts for jet noise suppression based on controlling the evolution of the large-scale turbulence structures.",
"date": "2008-05",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190717-102320761",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190717-102320761",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Naval Air Systems Command (NAVAIR)"
},
{
"agency": "TTC Technologies"
}
]
},
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"id": "2008-2890",
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"id": "Munson-M-J",
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{
"id": "Gharib-M",
"name": {
"family": "Gharib",
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},
"title": "A New Low Reynolds Number Facility for Active Flow Control Applications",
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"keywords": "Aerospace Systems, Operations and Life Cycle",
"note": "\u00a9 2008 by Matthew Munson. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 19 Jun 2012. \n\nThis effort supported by a Multidisciplinary Research Initiative from the United States Air Force Office of Scientific Research (FA9550-05-1-0369, Program Manager: Dr. Fariba Fahroo).\n\nPublished - MunsonDicksonColoniusEtAl2008.pdf
",
"abstract": "Recent interest in gaining understanding of the dynamics and behavior of the leading-edge vortex structure observed in biological flight systems has prompted the construction of a new low Reynolds number facility. This facility, a recirculating oil tunnel, gives several distinct advantages over similar facilities, utilizing water or air as the working fluid, for this kind of study. Additionally, as understanding is gained, active flow control strategies leading to the stabilization of the leading-edge vortex structure will be investigated, and this facility is specially equipped to enable this study. The tunnel has been designed and installed at the California Institute of Technology Graduate Aeronautical Laboratories. Design features of the facility will be discussed, along with some preliminary measurements conducted on a NACA 0012 wing.",
"date": "2008-01",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190717-102321018",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190717-102321018",
"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": "FA9550-05-1-0369"
}
]
},
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"id": "2008-694",
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"author_list": "Munson, Matthew J.; Dickson, William B.; et el."
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"items": [
{
"id": "Joe-Won-Tae",
"name": {
"family": "Joe",
"given": "Won Tae"
}
},
{
"id": "Taira-Kunihiko",
"name": {
"family": "Taira",
"given": "Kunihiko"
},
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},
{
"id": "Colonius-T",
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{
"id": "MacMartin-D-G",
"name": {
"family": "MacMynowski",
"given": "Douglas G."
},
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},
{
"id": "Tadmor-G",
"name": {
"family": "Tadmor",
"given": "Gilead"
}
}
]
},
"title": "Closed-Loop Control of Vortex Shedding on a Two-Dimensional Flat-Plate Airfoil at a Low Reynolds Number",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aerospace Systems, Operations and Life Cycle",
"note": "\u00a9 2008 by the authors. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 19 Jun 2012. \n\nWork supported by a Multidisciplinary Research Initiative from the United States Air Force Office of Scientific Research (FA9550-05-1-0369, Program Manager: Dr. Fariba Fahroo).\n\nSubmitted - JoeTairaColoniusEtAl2008.pdf
",
"abstract": "Open- and closed-loop control of vortex shedding in two-dimensional flow over a flat plate at high angles of attack is numerically investigated at a Reynolds number of 300. Unsteady actuation is modeled as a body force near the leading or trailing edge, and is directed either upstream or downstream. For moderate angles of attack, sinusoidal forcing at the natural shedding frequency results in phase locking, with a periodic variation of lift at the same frequency. However, at sufficiently high angles of attack, subharmonics of the forcing frequency are also excited and the average lift over the forcing period varies from cycle to cycle in a complex manner. It is observed that the periods with the highest averaged lift are associated with particular phase difference between the forcing and the lift. We design a feedback algorithm to lock the forcing with the phase shift associated with the highest period-averaged lift. It is shown that the compensator results in a stable phaselocked limit cycle for a larger range of forcing frequencies than the open-loop control, and that it is able to stabilize otherwise unstable high-lift limit cycles that cannot be obtained with open-loop control. For example at an angle of attack of 40\u00b0, the feedback controller can increase the averaged lift coefficient from 1.35 to 2.43, an increase of 80%.",
"date": "2008-01",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190717-102318299",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190717-102318299",
"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": "FA9550-05-1-0369"
}
]
},
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{
"id": "2008-634",
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]
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"author_list": "Joe, Won Tae; Taira, Kunihiko; et el."
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"items": [
{
"id": "Williams-D",
"name": {
"family": "Williams",
"given": "D."
}
},
{
"id": "Collins-J",
"name": {
"family": "Collins",
"given": "J."
}
},
{
"id": "Jankhot-C",
"name": {
"family": "Jankhot",
"given": "C."
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "T."
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Tadmor-G",
"name": {
"family": "Tadmor",
"given": "Gilead"
}
}
]
},
"title": "Control of Flow Structure on a Semi-Circular Planform Wing",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aerospace Systems, Operations and Life Cycle",
"note": "\u00a9 2008 by David R. Williams. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 19 Jun 2012. \n\nThe support for this work by the U.S. Air Force Office of Scientific Research MURI (FA9550-05-1-0369) with program manager Dr. Fariba Fahroo is gratefully acknowledged. We are also appreciative of the support for Jesse Collins from the Illinois NASA Space Grant Consortium.\n\nPublished - WilliamsCollinsJankhotEtAl2008.pdf
",
"abstract": "Active flow control is used to modify the lift, drag and pitching moments on a semicircular wing with aspect ratio, AR = 2, and chord Reynolds number is 68,000. The wing is mounted on a pitch/plunge sting mechanism that responds to the instantaneous loads and moments acting on the wing. The leading edge of the airfoil contains 16 spatially localized actuators that can be independently controlled. Smoke wire visualization, surface pressure and six-component force balance measurements are used to characterize the effects of openloop forcing. The lift coefficients on the steady wing are enhanced with the actuation, similar to the effect of dynamic stall vortex lift enhancement that occurs during a pitch up maneuver. Surface pressure measurements are being used to construct a flow model for use in feedback control. Progress toward the goal of designing a feedback controller to stabilize the flight of the model in an oscillatory freestream is discussed.",
"date": "2008-01",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190717-102320045",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190717-102320045",
"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": "FA9550-05-1-0369"
},
{
"agency": "Illinois Space Grant Consortium"
}
]
},
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{
"id": "2008-597",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2008-597",
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"author_list": "Williams, D.; Collins, J.; et el."
},
{
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"lastmod": "2023-10-20 22:06:50",
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"items": [
{
"id": "Franck-J-A",
"name": {
"family": "Franck",
"given": "Jennifer A."
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Large-Eddy Simulation of Separation Control for Compressible Flow Over a Wall-Mounted Hump",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aerospace Systems, Operations and Life Cycle",
"note": "\u00a9 2008 by Jennifer A. Franck and Tim Colonius. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 19 Jun 2012. \n\nThis work was partially supported by a National Science Foundation graduate student fellowship. Computational resources provided by the Department of Defense High Performance Computing Centers.\n\nPublished - FranckColonius2008.pdf
",
"abstract": "Compressible large-eddy simulations of turbulent flow over a wall-mounted hump with active flow control are performed and compared to previous experiments. We consider a range of Mach numbers from 0.1 to 0.6. Control is applied just before the natural separation point via steady suction and zero-net mass flux oscillatory forcing. Compared with the baseline flow, control shortens the separation bubble length, but is generally found to be less effective at compressible Mach numbers. The LES matches well to the available experimental data for the baseline and steady suction cases. With oscillatory forcing, the LES captures the major flow physics of the large scale shedding of vortical structures, but over-predicts the separation bubble length at low Mach numbers.",
"date": "2008-01",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190718-165125724",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190718-165125724",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "NSF Graduate Research Fellowship"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2008-555",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2008-555",
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"pub_year": "2008",
"author_list": "Franck, Jennifer A. and Colonius, Tim"
},
{
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"eprint_id": 97256,
"eprint_status": "archive",
"datestamp": "2023-08-19 21:58:32",
"lastmod": "2023-10-20 22:06:54",
"type": "conference_item",
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"creators": {
"items": [
{
"id": "Brunton-S-L",
"name": {
"family": "Brunton",
"given": "Steven L."
}
},
{
"id": "Rowley-C-W",
"name": {
"family": "Rowley",
"given": "Clarence W."
},
"orcid": "0000-0002-9099-5739"
},
{
"id": "Taira-Kunihiko",
"name": {
"family": "Taira",
"given": "Kunihiko"
},
"orcid": "0000-0002-3762-8075"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Collins-Jesse",
"name": {
"family": "Collins",
"given": "Jesse"
}
},
{
"id": "Williams-D-R",
"name": {
"family": "Williams",
"given": "David R."
}
}
]
},
"title": "Unsteady Aerodynamic Forces on Small-Scale Wings: Experiments, Simulations, and Models",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aerospace Systems, Operations and Life Cycle",
"note": "\u00a9 2008 by the authors. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 19 Jun 2012.\n\nPublished - BruntonRowleyTairaEtAl2008.pdf
",
"abstract": "The goal of this work is to develop low order dynamical systems models for the unsteady lift and drag forces on small wings in various modes of flight, and to better understand the physical characteristics of unsteady laminar separation. Velocity field and body force data for a flat plate at static angle of attack and in sinusoidal pitch and plunge maneuvers are generated by 2D direct numerical simulations using an immersed boundary method at Re = 100. The lift of a sinusoidally plunging plate is found to deviate from the quasi-steady approximation at a reduced frequency of k = 0.5 over a range of Strouhal numbers. Lagrangian coherent structures illustrate formation and convection of a leading-edge vortex in sinusoidal pitch and plunge. A phenomenological ODE model with three states is shown to reproduce the lift on a flat plate at a static angle of attack above the stall angle. DNS for a 3D pitch-up maneuver of a rectangular plate at Re = 300 shows the effect of aspect ratio on vortical wake structure and lift. Wind tunnel experiments of a wing in single pitch-up and sinusoidal pitch maneuvers are compared with a dynamic model incorporating time delays and relaxation times to produce hysteresis.",
"date": "2008-01",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190718-165125978",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190718-165125978",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"other_numbering_system": {
"items": [
{
"id": "2008-520",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2008-520",
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"basename": "BruntonRowleyTairaEtAl2008.pdf",
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},
"resource_type": "conference_item",
"pub_year": "2008",
"author_list": "Brunton, Steven L.; Rowley, Clarence W.; et el."
},
{
"id": "https://authors.library.caltech.edu/records/rd6j7-tdz57",
"eprint_id": 97259,
"eprint_status": "archive",
"datestamp": "2023-08-19 20:09:50",
"lastmod": "2023-10-20 22:07:08",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Br\u00e8s-G-A",
"name": {
"family": "Br\u00e8s",
"given": "Guillaume A."
},
"orcid": "0000-0003-2507-8659"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Direct Numerical Simulations of Three-Dimensional Cavity Flows",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 2007 by G. A. Br\u00e8s & T. Colonius. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 4 Nov 2012. \n\nThis work was supported by AFOSR under grant F49620-02-1-0362. Computer time was provided in part by the Department of Defense High Performance Computing Centers. Part of this work was done in collaboration with Pr. V. Theofilis from the School of Aeronautics, Universidad Politecnica de Madrid.\n\nPublished - BresColonius2007a.pdf
",
"abstract": "Three-dimensional direct numerical simulations of the full compressible Navier\u2013Stokes equations are performed for cavities that are homogeneous in the spanwise direction. The formation of oscillating spanwise structures is observed inside the cavity. We show that this 3D instability arises from a generic centrifugal instability mechanism associated with the mean recirculating vortical flow in the downstream part of the cavity. In general, the three-dimensional mode has a spanwise wavelength of approximately 1 cavity depth and oscillates with a frequency about an order-of-magnitude lower than 2D Rossiter (flow/acoustics) instabilities. The 3D mode properties are in excellent agreement with predictions from our previous linear stability analysis. When present, the shear-layer (Rossiter) oscillations experience a low-frequency modulation that arises from nonlinear interactions with the three-dimensional mode. We connect these results with the observation of low-frequency modulations and spanwise structures in previous experimental and numerical studies on open cavity flows. Preliminary results on the connections between the 3D centrifugal instabilities and the presence/suppression of the wake mode are also presented.",
"date": "2007-05",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190718-165126239",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190718-165126239",
"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": "F49620-02-1-0362"
}
]
},
"other_numbering_system": {
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{
"id": "2007-3405",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2007-3405",
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},
"resource_type": "conference_item",
"pub_year": "2007",
"author_list": "Br\u00e8s, Guillaume A. and Colonius, Tim"
},
{
"id": "https://authors.library.caltech.edu/records/zg6ay-f1h85",
"eprint_id": 97262,
"eprint_status": "archive",
"datestamp": "2023-08-19 19:29:16",
"lastmod": "2023-10-20 22:07:20",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Williams-D",
"name": {
"family": "Williams",
"given": "D."
}
},
{
"id": "Doshi-S",
"name": {
"family": "Doshi",
"given": "S."
}
},
{
"id": "Collins-J",
"name": {
"family": "Collins",
"given": "J."
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "T."
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Control of the Spanwise Distribution of Circulation on NACA 0012 and Flat Plate Wings",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aerospace Systems, Operations and Life Cycle",
"note": "\u00a9 2007 by David R. Williams. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 18 Jun 2012. \n\nThe support for this work by the U.S. Air Force Office of Scientific Research MURI (FA9550-05-1-0369) with program manager Dr. Fariba Fahroo is gratefully acknowledged. We are also appreciative of the assistance of Crystal Lybolt with support from the Illinois NASA Space Grant Consortium.\n\nPublished - WilliamsDoshiCollinsEtAl2007.pdf
",
"abstract": "Open-loop active flow control is used to modify the spanwise distribution of circulation around an NACA 0012 and flat plate wing. The leading edge on both airfoils and tip regions of the NACA airfoil contain spatially localized actuators that can be independently controlled in terms of amplitude and frequency, allowing the spanwise distribution of circulation to be modified. Different orientations of the pulsed-blowing actuators were used to provide upstream, downstream, in-line with the flow, and outward span components of actuation. The actuation effectiveness was documented using force balance measurements of the lift and drag, smoke-wire visualization, surface pressure measurements and PIV velocity field measurements. Actuation with an upstream component is shown to be far more effective in reducing the separated region than actuation in the streamwise direction. Initial measurements of the change in circulation on the suction surface of the airfoil indicate that spatially localized forcing produces global changes over the wing, primarily associated with the reduction in size of the separated flow region.",
"date": "2007-01",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190718-165126500",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190718-165126500",
"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": "FA9550-05-1-0369"
},
{
"agency": "Illinois Space Grant Consortium"
}
]
},
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{
"id": "2007-1121",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2007-1121",
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"url": "https://authors.library.caltech.edu/records/zg6ay-f1h85/files/WilliamsDoshiCollinsEtAl2007.pdf"
},
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"pub_year": "2007",
"author_list": "Williams, D.; Doshi, S.; et el."
},
{
"id": "https://authors.library.caltech.edu/records/g50jc-hpg03",
"eprint_id": 97251,
"eprint_status": "archive",
"datestamp": "2023-08-19 19:29:06",
"lastmod": "2023-10-20 22:06:43",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Ahuja-Sunil",
"name": {
"family": "Ahuja",
"given": "Sunil"
}
},
{
"id": "Rowley-C-W",
"name": {
"family": "Rowley",
"given": "Clarence W."
},
"orcid": "0000-0002-9099-5739"
},
{
"id": "Kevrekidis-I-G",
"name": {
"family": "Kevrekidis",
"given": "Ioannis G."
}
},
{
"id": "Wei-Mingjun",
"name": {
"family": "Wei",
"given": "Mingjun"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Tadmor-G",
"name": {
"family": "Tadmor",
"given": "Gilead"
}
}
]
},
"title": "Low-Dimensional Models for Control of Leading-Edge Vortices: Equilibria and Linearized Models",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aerospace Systems, Operations and Life Cycle",
"note": "\u00a9 2007 by the authors. Published by the American Institute of Aeronautics and Astronautics, Inc. with permission. \n\nPublished Online: 18 Jun 2012. \n\nWe gratefully acknowledge Sam Taira for help with the immersed boundary simulations, and Liang Qiao for help with timestepper based analysis of steady states. This research was supported by AFOSR, grants FA9550-05-1-0369 and FA9550-06-1-0371.\n\nPublished - AhujaRowleyKevrekidisEtAl2007.pdf
",
"abstract": "When an airfoil is pitched up rapidly, a dynamic stall vortex forms at the leading edge and produces high transient lift before shedding and stall occur. The aim of this work is to develop low-dimensional models of the dynamics of these leading-edge vortices, which may be used to develop feedback laws to stabilize these vortices using closed-loop control, and maintain high lift. We first perform a numerical study of the two-dimensional incompressible flow past an airfoil at varying angles of attack, finding steady states using a timestepper-based Newton/GMRES scheme, and dominant eigenvectors using ARPACK. These steady states may be either stable or unstable; we develop models linearized about the stable steady states using a method called Balanced Proper Orthogonal Decomposition, an approximation of balanced truncation that is tractable for large systems. The balanced POD models dramatically outperform models using the standard POD/Galerkin procedure, and are used to develop observers that reconstruct the flow state from a single surface pressure measurement.",
"date": "2007-01",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190718-165125547",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190718-165125547",
"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": "FA9550-05-1-0369"
},
{
"agency": "Air Force Office of Scientific Research (AFOSR)",
"grant_number": "FA9550-06-1-0371"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2007-709",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2007-709",
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"basename": "AhujaRowleyKevrekidisEtAl2007.pdf",
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},
"resource_type": "conference_item",
"pub_year": "2007",
"author_list": "Ahuja, Sunil; Rowley, Clarence W.; et el."
},
{
"id": "https://authors.library.caltech.edu/records/q6gyy-kp129",
"eprint_id": 97260,
"eprint_status": "archive",
"datestamp": "2023-08-19 19:29:11",
"lastmod": "2023-10-20 22:07:12",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Br\u00e8s-G-A",
"name": {
"family": "Br\u00e8s",
"given": "Guillaume A."
},
"orcid": "0000-0003-2507-8659"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Three-Dimensional Linear Stability Analysis of Cavity Flows",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aerospace Systems, Operations and Life Cycle",
"note": "\u00a9 2007 by G.A. Br\u00e8s & T. Colonius. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 18 Jun 2012. \n\nThis work was supported by AFOSR under grant F49620-02-1-0362. Computer time was provided in part by the Department of Defense High Performance Computing Centers. Part of this work was done in collaboration with Pr. V. Theofilis from the School of Aeronautics, Universidad Politecnica de Madrid.\n\nPublished - BresColonius2007.pdf
",
"abstract": "Numerical Simulations of the two- and three-dimensional linearized Navier\u2013Stokes equations are performed to investigate instabilities of open cavity flows that are homogeneous in the spanwise direction. First, the onset of two-dimensional cavity instability is characterized over a range of Mach numbers, Reynolds numbers and cavity aspect ratios. The resulting oscillations are consistent with the typical Rossiter flow/acoustic resonant modes. We then identify the presence of three-dimensional instabilities of the two-dimensional basic flow and study their dependence on the parameter space. In general, the most amplified three-dimensional mode has a spanwise wavelength scaling with the cavity depth, and a frequency typically an order-of-magnitude smaller than two-dimensional Rossiter modes. The instability appears to arise from a generic centrifugal instability mechanism associated with a large vortex in the two-dimensional basic flow that occupies the downstream portion within the cavity.",
"date": "2007-01",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190718-165126320",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190718-165126320",
"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": "F49620-02-1-0362"
}
]
},
"other_numbering_system": {
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{
"id": "2007-1126",
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]
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"pub_year": "2007",
"author_list": "Br\u00e8s, Guillaume A. and Colonius, Tim"
},
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"id": "https://authors.library.caltech.edu/records/e5m7e-s3b33",
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"lastmod": "2023-10-20 22:07:47",
"type": "conference_item",
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"creators": {
"items": [
{
"id": "Taira-Kunihiko",
"name": {
"family": "Taira",
"given": "Kunihiko"
},
"orcid": "0000-0002-3762-8075"
},
{
"id": "Dickson-W-B",
"name": {
"family": "Dickson",
"given": "William B."
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Dickinson-M-H",
"name": {
"family": "Dickinson",
"given": "Michael H."
},
"orcid": "0000-0002-8587-9936"
},
{
"id": "Rowley-C-W",
"name": {
"family": "Rowley",
"given": "Clarence W."
},
"orcid": "0000-0002-9099-5739"
}
]
},
"title": "Unsteadiness in Flow over a Flat Plate at Angle-of-Attack at Low Reynolds Numbers",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aerospace Systems, Operations and Life Cycle",
"note": "\u00a9 2007 by the authors. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 18 Jun 2012. \n\nWork supported by a Multidisciplinary Research Initiative from the United States Air Force Office of Scientific Research (FA9550-05-1-0369, Program Manager: Dr. Fariba Fahroo).\n\nPublished - TairaDicksonColoniusEtAl2007.pdf
",
"abstract": "Flow over an impulsively started low-aspect-ratio flat plate at angle-of-attack is investigated for a Reynolds number of 300. Numerical simulations, validated by a companion experiment, are performed to study the influence of aspect ratio, angle of attack, and planform geometry on the interaction of the leading-edge and tip vortices and resulting lift and drag coefficients. Aspect ratio is found to significantly influence the wake pattern and the force experienced by the plate. For large aspect ratio plates, leading-edge vortices evolved into hairpin vortices that eventually detached from the plate, interacting with the tip vortices in a complex manner. Separation of the leading-edge vortex is delayed to some extent by having convective transport of the spanwise vorticity as observed in flow over elliptic, semicircular, and delta-shaped planforms. The time at which lift achieves its maximum is observed to be fairly constant over different aspect ratios, angles of attack, and planform geometries during the initial transient. Preliminary results are also presented for flow over plates with steady actuation near the leading edge.",
"date": "2007-01",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190718-165127033",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190718-165127033",
"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": "FA9550-05-1-0369"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2007-710",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2007-710",
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"basename": "TairaDicksonColoniusEtAl2007.pdf",
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},
"resource_type": "conference_item",
"pub_year": "2007",
"author_list": "Taira, Kunihiko; Dickson, William B.; et el."
},
{
"id": "https://authors.library.caltech.edu/records/3h917-p4w37",
"eprint_id": 97280,
"eprint_status": "archive",
"datestamp": "2023-08-22 07:08:14",
"lastmod": "2023-10-20 22:08:38",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Johnsen-E",
"name": {
"family": "Johnsen",
"given": "Eric"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Numerical Study of the Collapse of a Bubble Subjected to a Lithotripter Pulse",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Organs; Shock waves; Reentrant; Medical diagnosis",
"note": "\u00a9 2006 Acoustical Society of America. \n\nPublished Online: 24 October 2006. \n\nThis work was supported by NIH Grant PO1 DK043881.",
"abstract": "In shock wave lithotripsy, the combined effect of focused shock waves and cavitation pulverizes kidney stones. Although cavitation has been shown to play an important role in the stone comminution process, the underlying mechanism has yet to be fully understood. The goal of the present study is to quantify the potential damage caused by the collapse of a single bubble near a solid surface. Using a high\u2010order accurate quasiconservative, shock\u2010 and interface\u2010capturing scheme [E. Johnsen and T. Colonius, J. Comput. Phys., in press (2006)], the response of an air bubble subjected to a lithotripter pulse is considered. In particular, quantities important in cavitation erosion, such as wall stresses and reentrant jet velocity, are measured as functions of the properties of the pulse (amplitude, wavelength) and the geometry of the problem (stand\u2010off distance from the wall, presence of neighboring bubbles). Preliminary two\u2010dimensional results for a ''cylindrical bubble'' show that a large water\u2010hammer pressure is measured along the wall. This pressure increases for smaller stand\u2010off distances and longer wavelengths. Further results for spherical bubbles will be presented at the meeting.",
"date": "2006-11",
"date_type": "published",
"publisher": "The Journal of the Acoustical Society of America",
"id_number": "CaltechAUTHORS:20190718-165128473",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190718-165128473",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "NIH",
"grant_number": "PO1 DK043881"
}
]
},
"doi": "10.1121/1.4787344",
"resource_type": "conference_item",
"pub_year": "2006",
"author_list": "Johnsen, Eric and Colonius, Tim"
},
{
"id": "https://authors.library.caltech.edu/records/8tye4-y3v75",
"eprint_id": 97271,
"eprint_status": "archive",
"datestamp": "2023-08-19 17:11:27",
"lastmod": "2023-10-20 22:08:00",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Suzuki-Takao",
"name": {
"family": "Suzuki",
"given": "Takao"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Relation Between Instability Waves and Low-Frequency Jet Noise Investigated with Phased-Microphone Arrays",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aerospace Systems, Operations and Life Cycle",
"note": "\u00a9 2006 by T. Suzuki and T. Colonius. Published by the American Institute of Aeronautics and Astronautics, lnc., with permission. \n\nPublished Online: 21 Jun 2012. \n\nThe authors acknowledge the support of an AeroAcoustics Research Consortium (AARC) grant from the Ohio Aerospace Institute (OAI). We would like to express our deepest appreciation to Drs. J. Bridges, S.-S. Lee, and their colleagues at NASA Glenn Research Center for conducting all the experiments and fruitful discussions.\n\nPublished - SuzukiColonius2006a.pdf
",
"abstract": "We study the relation between sound radiation patterns and the azimuthal-mode balance of instability-wave amplitude in a subsonic jet using mid-field and near-field phased- microphone arrays. To identify instability waves, we apply a least square optimization method, i.e. a beam-forming algorithm, to pressure signals obtained from a conical microphone array surrounding the jet from the nozzle exit to the end of the potential core. For the reference solutions, we use eigenfunctions based on linear stability analysis using the turbulent mean-velocity profiles and infer the amplitude of the axisymmetric and first two azimuthal modes associated with the Kelvin\u2014Helmholtz instabilities. Likewise, pressure signals obtained from the mid-field array are decomposed into the azimuthal modes, and the directivity of low-frequency noise, particularly that of coherent sound, is analyzed. The azimuthal mode balances of the instability waves and acoustic waves are then compared, and the effects of compressibility, jet temperature and nozzle type (i.e. straight and chevron nozzles) are investigated. The results show that the directivity of low-frequency jet noise changes from the quadrupole radiation patterns to highly directive ones as increasing Mach number, while all instability modes are suppressed owing to compressibility without substantially varying the azimuthal-mode balance. The correlation of the azimuthal-mode balance between instability waves and coherent sound is stronger at higher Mach numbers. We also find that the radiation patterns of low-frequency noise change from quadrupoles to dipoles as the temperature increases at a low Mach number.",
"date": "2006-01",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190718-165127273",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190718-165127273",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Ohio Aerospace Institute"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2006-622",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2006-622",
"primary_object": {
"basename": "SuzukiColonius2006a.pdf",
"url": "https://authors.library.caltech.edu/records/8tye4-y3v75/files/SuzukiColonius2006a.pdf"
},
"resource_type": "conference_item",
"pub_year": "2006",
"author_list": "Suzuki, Takao and Colonius, Tim"
},
{
"id": "https://authors.library.caltech.edu/records/0s615-kqj40",
"eprint_id": 97274,
"eprint_status": "archive",
"datestamp": "2023-08-19 15:44:58",
"lastmod": "2023-10-20 22:08:12",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Reba-R-A",
"name": {
"family": "Reba",
"given": "R."
}
},
{
"id": "Narayanan-S",
"name": {
"family": "Narayanan",
"given": "S."
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "T."
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Suzuki-Takao",
"name": {
"family": "Suzuki",
"given": "T."
}
}
]
},
"title": "Modeling Jet Noise from Organized Structures Using Near-Field Hydrodynamic Pressure",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 2005 by the author(s). Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 11 Nov 2012. \n\nThe authors are indebted to Drs. J. Bridges and S.-S. Lee for generously sharing their data and for fruitful discussions. TC and TS gratefully acknowledge the support of a grant from the Aeroacoustics Research Consortium (AARC) of the Ohio Aerospace Institute.\n\nPublished - RebaNarayananColoniusEtAl2005.pdf
",
"abstract": "A wave-packet ansatz is used to model noise generation by organized, large-scale structures. The spectrum of the acoustic field is expressed in terms of two-point space-time correlations of hydrodynamic pressure on a conical surface surrounding the jet plume. The surface is sufficiently near the turbulent flow region to be dominated by hydrodynamic disturbances, yet sufficiently far that the wave equation can be used to project the nearfield pressure to the acoustic field. In the present study, a 78-microphone array was used to measure hydrodynamic pressure on the conical surface at a variety of acoustic Mach numbers and temperature ratios. At each jet cross section, 6 microphones are staggered in the azimuthal direction allowing resolution of pressure up to azimuthal mode number m = 2. We compare recent jet noise measurements using an 80-microphone conical mid-field array with those derived from the near-field hydrodynamic array data, showing reasonably good predictions. Source model parameters are identified for various jet temperature ratios. Results show that changes in jet noise directivity with heating can be attributed to contraction of the wave-packet scale.",
"date": "2005-05",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190718-165127504",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190718-165127504",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Ohio Aerospace Institute"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2005-3093",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2005-3093",
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"basename": "RebaNarayananColoniusEtAl2005.pdf",
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},
"resource_type": "conference_item",
"pub_year": "2005",
"author_list": "Reba, R.; Narayanan, S.; et el."
},
{
"id": "https://authors.library.caltech.edu/records/4ex9f-gvt30",
"eprint_id": 97265,
"eprint_status": "archive",
"datestamp": "2023-08-19 13:41:57",
"lastmod": "2023-10-20 22:07:36",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Theofilis-V",
"name": {
"family": "Theofilis",
"given": "V."
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "T."
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Three-dimensional instabilities of compressible flow over open cavities: direct solution of the BiGlobal eigenvalue problem",
"ispublished": "unpub",
"full_text_status": "public",
"note": "\u00a9 2004 by the American Institute of Aeronautics and Astronautics, Inc. \n\nPublished Online: 19 Jun 2012. \n\nThe material is based upon work supported by the European Office of Aerospace Research and Development, Air Force Research Laboratory, Air Force Office of Scientific Research, under Grants No. F49620-02-1-0362 (Caltech) and FA8655-03-1-3059 (nu modelling S.L.) monitored by Dr. John D. Schmisseur (AFOSR) and Mr. Wayne Donaldson (EOARD).\n\nPublished - TheofilisColonius2004.pdf
",
"abstract": "We report progress in our ongoing effort to compute and understand the instabilities of open cavity flows from incompressible to supersonic speeds. We consider three-dimensional instabilities of nominally two dimensional (spanwise homogeneous) cavity flows (BiGlobal instabilities). Experiments, DNS/LES computations, and preliminary instability computations have shown that the modes of oscillation are influenced by complex interactions between the shear layer and the recirculating flow within the cavity. We present here a framework for computation of the two-dimensional eigenvalue problem for the compressible open cavity. We validate the numerical scheme by computing several canonical flows: square duct flow, boundary layers at speeds from incompressible to supersonic, and two-dimensional parallel shear layers. We present preliminary results for the three-dimensional modes of the compressible open cavity flow with length-to-depth ratio of two at a Mach number of 0.325.",
"date": "2004-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190718-165126795",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190718-165126795",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "European Office of Aerospace Research and Development"
},
{
"agency": "Air Force Research Laboratory (AFRL)"
},
{
"agency": "Air Force Office of Scientific Research (AFOSR)",
"grant_number": "F49620-02-1-0362"
},
{
"agency": "Air Force Office of Scientific Research (AFOSR)",
"grant_number": "FA8655-03-1-3059"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2004-2544",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2004-2544",
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"basename": "TheofilisColonius2004.pdf",
"url": "https://authors.library.caltech.edu/records/4ex9f-gvt30/files/TheofilisColonius2004.pdf"
},
"resource_type": "conference_item",
"pub_year": "2004",
"author_list": "Theofilis, V. and Colonius, T."
},
{
"id": "https://authors.library.caltech.edu/records/5g3ht-by565",
"eprint_id": 97272,
"eprint_status": "archive",
"datestamp": "2023-08-19 13:33:48",
"lastmod": "2023-10-20 22:08:04",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Suzuki-Takao",
"name": {
"family": "Suzuki",
"given": "Takao"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Identification of Jet Instability Waves and Design of a Microphone Array",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 2004 by Takao Suzuki and Tim Colonius. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 11 Nov 2012. \n\nThe authors would like to acknowledge partial support of the AeroAcoustics Research Consortium (AARC) grant from the Ohio Aerospace Institute (OAI). We sincerely appreciate the experiments conducted by Drs. J. Bridges, S.-S. Lee, and their colleagues at NASA Glenn Research Center as well as fruitful discussion with their group. We also thank Prof. J. Freund at the University of Illinois for the DNS database and Drs. S. Narayanan, R. Reba, and R. Schlinker at the United Technologies Research Center for technical discussion regarding jet noise experiments.\n\nPublished - SuzukiColonius2004.pdf
",
"abstract": "We propose a diagnostic technique to detect instability waves in a round jet using a conical microphone array. The detection algorithm is analogous to the beam-forming technique, which is used with a far-field microphone array to localize noise sources. By replacing the reference solutions used in the conventional beam-forming with eigenfunctions from a linear stability analysis, the amplitude of the low-frequency azimuthal instability waves can be inferred. We use a DNS database and experimental measurements of the mean flow to design a phased microphone array which is placed just outside the shear layer near the nozzle exit. We validate the technique in experiments by checking for consistency of the radial decay, phase correlation, and streamwise evolution of the hydrodynamic pressure. The comparison between the experiment and linear stability analysis shows good agreement, particularly near the most amplified frequency of each azimuthal mode.",
"date": "2004-05",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190718-165127351",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190718-165127351",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Ohio Aerospace Institute"
}
]
},
"other_numbering_system": {
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{
"id": "2004-2960",
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"author_list": "Suzuki, Takao and Colonius, Tim"
},
{
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"items": [
{
"id": "Ran-Hongyu",
"name": {
"family": "Ran",
"given": "Hongyu"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Numerical Simulation of Sound Radiated from a Turbulent Vortex Ring",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 2004 by Hongyu Ran and Tim Colonius. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 11 Nov 2012. \n\nThis research was supported in part by the National Science Foundation (Grant CTS-9501349).\n\nPublished - RanColonius2004.pdf
",
"abstract": "The acoustic field radiated by a turbulent vortex ring is studied. Direct Numerical Simulations (DNS) of the fully compressible, three-dimensional Navier-Stokes equations are used to generate an axisymmetric vortex ring to which 3D stochastic disturbances are added. The disturbances cause instability and turbulent transition of the vortex ring. Detailed information about temporal evolution of sound pressure level, spectrum and directivity associated with each mode is investigated. The peak frequency agrees well with experiments, and the directivity of each azimuthal mode agrees well with predictions of vortex sound theory. Based on the self-similar decay of the turbulent near field, the selfsimilar decay of the sound field is investigated. We also explore the connections with jet noise by modeling the jet as a de-correlated train of vortex rings.",
"date": "2004-05",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190718-165128101",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190718-165128101",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "NSF",
"grant_number": "CTS-9501349"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2004-2918",
"name": "AIAA Paper"
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"author_list": "Ran, Hongyu and Colonius, Tim"
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"creators": {
"items": [
{
"id": "Suzuki-Takao",
"name": {
"family": "Suzuki",
"given": "Takao"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "MacMartin-D-G",
"name": {
"family": "MacMartin",
"given": "Douglas G."
},
"orcid": "0000-0003-1987-9417"
}
]
},
"title": "Closed-Loop Control of Vortex Shedding in a Separated Diffuser Using an Inverse Method",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aerospace Systems, Operations and Life Cycle",
"note": "\u00a9 2004 by Takao Suzuki, Tim Colonius, and Douglas G. MacMartin. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 21 Jun 2012. \n\nWe would like to thank Prof. Hassan M. Nagib for many fruitful discussions on separation control.\n\nSubmitted - SuzukiColoniusMacMartin2004.pdf
",
"abstract": "We propose a closed-loop control algorithm for vortex shedding in a separated diffuser. We introduce pulses of zero-net-mass injection (consecutive blowing and suction) together with an inverse vortex imaging method. This method estimates the circulation of a vortex in the separated region based on pressure at a limited number of observer points at the wall. The closed-loop algorithm determines when to start the pulse so that the vortex is pinched off with a size which minimizes the stagnation pressure loss. We examine the proposed method in a simplified flow by performing direct numerical simulations of two-dimensional diffusers. In order to investigate the robustness of the closed-loop control algorithm, we impose high frequency acoustic disturbance upstream of the separation point. The disturbances significantly reduce the effectiveness of open-loop control compared to the case where no external disturbances are added. By using closed-loop control, however, performance is once again substantially recovered in the presence of disturbances.",
"date": "2004-01",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190718-165127197",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190718-165127197",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"other_numbering_system": {
"items": [
{
"id": "2004-577",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2004-577",
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"pub_year": "2004",
"author_list": "Suzuki, Takao; Colonius, Tim; et el."
},
{
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"creators": {
"items": [
{
"id": "Tanguay-M",
"name": {
"family": "Tanguay",
"given": "Michel"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
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"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Progress in Modeling and Simulation of Shock Wave Lithotripsy (SWL)",
"ispublished": "unpub",
"full_text_status": "public",
"note": "This work was supported by NIH under a Program Project Grant PO1 DK43881. We would like to thank Dr. Andrew Evan and all the PPG investigators. In particularly, we thank Dr's Robin Cleveland, Mike Bailey and Yura Pishchalnikov for their comments and experimental data.\n\nSubmitted - TanguayColonius2003.pdf
",
"abstract": "Past research in shock wave lithotripsy (SWL) has shown that cavitation plays an essential role in the comminution of kidney stones. To provide a better understanding of the role of cloud cavitation dynamics in SWL, the flow in the focal region of a lithotripter was modeled using an ensemble averaged two-phase flow model for the bubbly mixture combined with a high-order accurate shock capturing technique. The domain and initial conditions used in the numerical model reflect the appropriate dimensions and intensity of a Dornier HM3 electrohydraulic lithotripter. The impact of factors such as the size and number of bubble nuclei in the liquid, the intensity of the shock wave and the pulse rate frequency (PRF) on the cavitating flow field is analyzed. Conclusions regarding the impact of these parameters on the potential for stone comminution are also presented.",
"date": "2003-11",
"date_type": "published",
"publisher": "Caltech Library",
"id_number": "CaltechAUTHORS:20190718-165126954",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190718-165126954",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "NIH",
"grant_number": "PO1 DK43881"
}
]
},
"primary_object": {
"basename": "TanguayColonius2003.pdf",
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"pub_year": "2003",
"author_list": "Tanguay, Michel and Colonius, Tim"
},
{
"id": "https://authors.library.caltech.edu/records/x7w07-vzt76",
"eprint_id": 140,
"eprint_status": "archive",
"datestamp": "2023-08-22 01:02:09",
"lastmod": "2023-10-13 20:28:13",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Preston-A-T",
"name": {
"family": "Preston",
"given": "A."
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "T."
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Brennen-C-E",
"name": {
"family": "Brennen",
"given": "C. E."
}
}
]
},
"title": "Reduced-Order Modeling of Diffusive Effects on the Dynamics of Bubbles",
"ispublished": "unpub",
"full_text_status": "public",
"note": "Published - PRE221.pdf
",
"abstract": "The Rayleigh-Plesset equation and its extensions have been used extensively to model spherical bubble dynamics, yet radial diffusion equations must be solved to correctly capture damping effects due to mass and thermal diffusion. The latter are too computationally intensive to implement into a continuum model for bubbly cavitating flows, since the diffusion equations must be solved at each position in the flow. The goal of the present research is to derive a reduced-order model that accounts for thermal and mass diffusion. Motivated by results of applying the Proper Orthogonal Decomposition to data from full radial computations, we derive a model based upon estimates of the average heat transfer coefficients. The model captures the damping effects of the diffusion processes in two ordinary differential equations, and gives better results than previous models.",
"date": "2003-11",
"date_type": "published",
"publisher": "Caltech Library",
"id_number": "CaltechAUTHORS:PREcav03",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:PREcav03",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"primary_object": {
"basename": "PRE221.pdf",
"url": "https://authors.library.caltech.edu/records/x7w07-vzt76/files/PRE221.pdf"
},
"resource_type": "conference_item",
"pub_year": "2003",
"author_list": "Preston, A.; Colonius, T.; et el."
},
{
"id": "https://authors.library.caltech.edu/records/00sd9-5vh54",
"eprint_id": 97250,
"eprint_status": "archive",
"datestamp": "2023-09-15 06:20:12",
"lastmod": "2023-10-23 21:25:28",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Bailey-M-R",
"name": {
"family": "Bailey",
"given": "Michael R."
}
},
{
"id": "Crum-L-A",
"name": {
"family": "Crum",
"given": "Lawrence A."
}
},
{
"id": "Sapozhnikov-O-A",
"name": {
"family": "Sapozhnikov",
"given": "Oleg A."
}
},
{
"id": "Evan-A-P",
"name": {
"family": "Evan",
"given": "Andrew P."
}
},
{
"id": "McAteer-J-A",
"name": {
"family": "McAteer",
"given": "James A."
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Cleveland-R-O",
"name": {
"family": "Cleveland",
"given": "Robin O."
}
}
]
},
"title": "Cavitation in shock wave lithotripsy",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Diseases and conditions; Hydrostatics; Chemical elements; Hydrophone; Shock waves; Organic compounds; Crack formation; Medical diagnosis",
"note": "\u00a9 2003 Acoustical Society of America. \n\nPublished Online: 08 October 2003. \n\nWork supported by NIH DK43381, DK55674, and FIRCA.",
"abstract": "A case is presented for the important role of cavitation in stone comminution and tissue injury in shock wave lithotripsy (SWL). Confocal hydrophones and a coincidence algorithm were used to detect cavitation in kidney parenchyma. Elevated hydrostatic pressure dissolved cavitation nuclei and suppressed cell injury and stone comminution in vitro. A low\u2010insertion\u2010loss, thin, mylar film nearly eliminated stone erosion and crack formation only when in direct contact with the stone. This result indicates not only that cavitation is important in both cracking and erosion but also that bubbles act at the surface. Time inversion of the shock wave by use of a pressure\u2010release reflector reduced the calculated pressure at bubble collapse and the measured depth of bubble\u2010induced pits in aluminum. Correspondingly tissue injury in vivo was nearly eliminated. Cavitation was localized and intensified by the use of synchronously triggered, facing lithotripters. This dual pulse lithotripter enhanced comminution at its focus and reduced lysis in surrounding blood samples. The enhancement of comminution was lost when stones were placed in glycerol, which retarded bubble implosion. Thus, cavitation is important in comminution and injury and can be controlled to optimize efficacy and safety.",
"date": "2003-10",
"date_type": "published",
"id_number": "CaltechAUTHORS:20190718-165125458",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190718-165125458",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "NIH",
"grant_number": "DK43381"
},
{
"agency": "NIH",
"grant_number": "DK55674"
},
{
"agency": "Fogarty International Research Collaboration Award"
}
]
},
"doi": "10.1121/1.4778635",
"resource_type": "conference_item",
"pub_year": "2003",
"author_list": "Bailey, Michael R.; Crum, Lawrence A.; et el."
},
{
"id": "https://authors.library.caltech.edu/records/5hjh7-bg971",
"eprint_id": 97254,
"eprint_status": "archive",
"datestamp": "2023-09-15 06:20:16",
"lastmod": "2023-10-23 21:25:30",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Tanguay-M",
"name": {
"family": "Tanguay",
"given": "Michel"
}
}
]
},
"title": "Cloud cavitation effects in shockwave lithotripsy",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Multiphase flows; Optical imaging; Organs; Shock waves; Bubble dynamics; Medical diagnosis",
"note": "\u00a9 2003 Acoustical Society of America. \n\nPublished Online: 08 October 2003.",
"abstract": "Cavitation has already been identified as an important damage mechanism in the comminution of kidney stones in shockwave lithotripsy (SWL). However, the precise conditions that maximize the damage caused by the collapsing bubbles are still unknown. Numerical simulations are used to investigate shock propagation and the consequent growth and collapse of a bubble cloud in the focal region of a lithotripter. In the simulations, a continuum two\u2010phase flow model for the ensemble\u2010averaged macroscale is coupled to a Gilmore model for individual spherical bubble dynamics at the microscale. The simulations show agreement with experimental pressure measurements and high\u2010speed photography of the bubble cloud. At void fractions commensurate with experiments, it is found that the collective collapse of the bubble cloud provides a significant increase to the energy available for comminution (beyond what a single bubble would produce). Relatively small increases in the pressure at the center of the cloud in advance of collapse (two orders of magnitude smaller than the initial shock) can more than double the energy of the collapsing bubble.",
"date": "2003-10",
"date_type": "published",
"id_number": "CaltechAUTHORS:20190718-165125806",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190718-165125806",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"doi": "10.1121/1.4779511",
"resource_type": "conference_item",
"pub_year": "2003",
"author_list": "Colonius, Tim and Tanguay, Michel"
},
{
"id": "https://authors.library.caltech.edu/records/epcjn-2qn64",
"eprint_id": 97277,
"eprint_status": "archive",
"datestamp": "2023-09-15 06:20:20",
"lastmod": "2023-10-23 21:25:32",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Pishchalnikov-Y-A",
"name": {
"family": "Pishchalnikov",
"given": "Yuri A."
}
},
{
"id": "McAteer-J-A",
"name": {
"family": "McAteer",
"given": "James A."
}
},
{
"id": "Evan-A-P",
"name": {
"family": "Evan",
"given": "Andrew P."
}
},
{
"id": "Sapozhnikov-O-A",
"name": {
"family": "Sapozhnikov",
"given": "Oleg A."
}
},
{
"id": "Cleveland-R-O",
"name": {
"family": "Cleveland",
"given": "Robin O."
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Bailey-M-R",
"name": {
"family": "Bailey",
"given": "Michael R."
}
},
{
"id": "Crum-L-A",
"name": {
"family": "Crum",
"given": "Lawrence A."
}
}
]
},
"title": "Dynamics of Concerted Bubble Cluster Collapse in Shock Wave Lithotripsy",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Fiber optics; Optical imaging; Organs; Hydrophone; Shock waves; Cavitation bubbles; Medical diagnosis",
"note": "\u00a9 2003 Acoustical Society of America. \n\nPublished Online: 08 October 2003. \n\nWork supported by NIH DK43881, DK55674.",
"abstract": "Cavitation bubble cluster collapse at the surface of artificial kidney stones during shock wave lithotripsy was investigated in vitro by means of multiframe high\u2010speed photography, passive cavitation detection (PCD), and pressure waveform measurements using a fiber\u2010optic probe hydrophone (FOPH). It was observed that after the passage of the lithotripter shock pulse the stone was covered by numerous individual bubbles. During their growth phase the bubbles coalesced into bubble clusters, with the biggest cluster at the proximal face of the stone. High\u2010speed camera images suggested that cluster collapse started at the periphery and ended with a violent collapse in a small region in the center of the surface of the stone. Shadowgraphy resolved numerous secondary shock waves emitted during this focused collapse. Shock wave emission during cluster collapse was confirmed by PCD. Measurement with the FOPH showed that these shock waves were typically of short duration (0.2 \u03bcs). The majority of the shock waves emanating from cluster collapse were low amplitude but some shock waves registered amplitudes on the order of the incident shock pulse (tens of MPa).",
"date": "2003-10",
"date_type": "published",
"id_number": "CaltechAUTHORS:20190718-165128182",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190718-165128182",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "NIH",
"grant_number": "DK43881"
},
{
"agency": "NIH",
"grant_number": "DK55674"
}
]
},
"doi": "10.1121/1.4777748",
"resource_type": "conference_item",
"pub_year": "2003",
"author_list": "Pishchalnikov, Yuri A.; McAteer, James A.; et el."
},
{
"id": "https://authors.library.caltech.edu/records/ypx61-vnr37",
"eprint_id": 97266,
"eprint_status": "archive",
"datestamp": "2023-08-19 11:34:42",
"lastmod": "2023-10-20 22:07:40",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Theofilis-V",
"name": {
"family": "Theofilis",
"given": "V."
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "T."
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "An Algorithm for the Recovery of 2- and 3-D BiGlobal Instabilities of Compressible Flow Over 2-D Open Cavities",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Fluid Dynamics",
"note": "\u00a9 2003 by the American Institute of Aeronautics and Astronautics, Inc. \n\nPublished Online: 25 Jun 2012. \n\nThe material is based upon work supported by the European Office of Aerospace Research and Development, Air Force Research Laboratory, Air Force Office of Scientific Research, under Grants No. FA8655-03-1-3059 and F49620-02-1-0362 monitored by Dr. John D. Schmisseur (AFOSR) and Mr. Wayne Donaldson (EOARD).\n\nPublished - TheofilisColonius2003.pdf
",
"abstract": "The identification of numerical residuals from direct numerical simulations (DNS) with the least-damped BiGlobal eigenmodes of an underlying steady-state permits extraction of both the steady-state and amplitude functions of the BiGlobal eigenmodes from simple algebraic operations. Algorithms for the calculation of the basic state and the spatial structure of the related BiGlobal eigenmodes from transient DNS data have been constructed and presented.\n\nHere we extend initial calculations for the (closed) incompressible lid-driven cavity to the related (compressible) open-cavity flow. Order-of-magnitude savings are demonstrated when using of the discussed algorithm for the calculation of the basic state, compared with straightforward time-integration of the equations of motion until convergence in time. Further, employing this algorithm, different classes of instabilities in the open cavity are unified in the framework of BiGlobal instability analysis.",
"date": "2003-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190718-165126872",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190718-165126872",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "European Office of Aerospace Research and Development"
},
{
"agency": "Air Force Research Laboratory (AFRL)"
},
{
"agency": "Air Force Office of Scientific Research (AFOSR)",
"grant_number": "FA8655-03-1-3059"
},
{
"agency": "Air Force Office of Scientific Research (AFOSR)",
"grant_number": "F49620-02-1-0362"
}
]
},
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{
"id": "2003-4143",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2003-4143",
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"basename": "TheofilisColonius2003.pdf",
"url": "https://authors.library.caltech.edu/records/ypx61-vnr37/files/TheofilisColonius2003.pdf"
},
"resource_type": "conference_item",
"pub_year": "2003",
"author_list": "Theofilis, V. and Colonius, T."
},
{
"id": "https://authors.library.caltech.edu/records/ttbjb-5ef11",
"eprint_id": 97269,
"eprint_status": "archive",
"datestamp": "2023-08-19 11:34:46",
"lastmod": "2023-10-20 22:07:51",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Suzuki-Takao",
"name": {
"family": "Suzuki",
"given": "Takao"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "MacMartin-D-G",
"name": {
"family": "MacMartin",
"given": "Douglas G."
},
"orcid": "0000-0003-1987-9417"
}
]
},
"title": "Inverse Technique for Vortex Imaging and Its Application to Feedback Flow Control",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Fluid Dynamics",
"note": "\u00a9 2003 by Takao Suzuki, Tim Colonius, and Douglas G. MacMartin. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 25 Jun 2012. \n\nWe appreciate Prof. Richard Murray for an idea of the estimator-corrector and Mr. Kazuo Sone for generating several files. The work on inverse algorithms described here was supported by DARPA (Defense Advanced Research Projects Agency) program (contract number F49620-00-C-0035).\n\nSubmitted - SuzukiColoniusMacMartin2003.pdf
",
"abstract": "A simple vortex imaging algorithm using a least square method is proposed for feedback flow control. The position and the circulation of a vortex convected in a channel are identified from the time history of pressure at a limited number of points on the wall. The capabilities of the algorithm are demonstrated using two-dimensional direct numerical simulations. A few observer points on one side of the wall are sufficient to detect the position and the circulation of a compact vortex to a reasonable degree of accuracy. This inverse algorithm is introduced to feedback separation control for a diffuser flow. The algorithm is modified for a curved channel, and the so-called \"estimator-corrector\" and \"fast algorithm\" are applied to reduce the uncertainty of prediction with less computational time. The DNS results demonstrate that the feedback control using the inverse technique can enhance the robustness against unsteady disturbances and lessen stagnation pressure loss.",
"date": "2003-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190718-165127116",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190718-165127116",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Defense Advanced Research Projects Agency (DARPA)",
"grant_number": "F49620-00-C-0035"
}
]
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"id": "2003-4260",
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}
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"items": [
{
"id": "Reba-R-A",
"name": {
"family": "Reba",
"given": "R."
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{
"id": "Narayanan-S",
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"given": "S."
}
},
{
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"title": "A Study of the Role of Organized Structures in Jet Noise Generation",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 2003 by United Technologies Corporation. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 4 Nov 2012. \n\nThis work is jointly funded by United Technologies Research Center and Pratt & Whitney. The authors would like to thank R. Schlinker and W. Lord for their support and fruitful discussions, Dr. Takao Suzuki for his assistance with signal processing of the DNS data, and Prabir Barooah and Keith Post for their assistance in acquiring the experimental data. The authors are grateful to Prof. Jon Freund for access to his database for the turbulent Mach 0.9 jet.\n\nSubmitted - RebaNarayananColoniusEtAl2003.pdf
",
"abstract": "We present analytical, experimental and computational studies aimed at understanding the role of large-scale, organized structures in noise generation from high-speed, compressible jets. Two-point near-field pressure data from experiments are analyzed and used to identify parameters in a wave-packet based model for noise generation from organized, large-scale structures. The statistical spectrum of far field pressure is expressed in terms of two-point space-time correlations of the near-field pressure on a surface enclosing the jet. The surface is assumed to be sufficiently near the turbulent region tobe dominated by non-propagating hydrodynamic disturbances, yet sufficiently far such that linear behavior can be assumed in extending the near-field pressure to the far field. Validity of such assumptions is investigated by interrogating the jet DNS database of Freund [J. Fluid Mech. 438:277-305 2001]. The DNS data analysis is also used to investigate the impact of limited spatial resolution in the experiments. The analytical model is used to study far field noise generation from organized structures. Results show that, for sufficiently short structure lifetime, aft angle far field pressure spectra tend to exhibit frequency scaling with Helmholtz number, rather than Strouhal number.",
"date": "2003-05",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190718-165128014",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190718-165128014",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "United Technologies Research Center"
},
{
"agency": "Pratt & Whitney"
}
]
},
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"id": "2003-3314",
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},
"title": "Large-Scale Unsteadiness in a Two-Dimensional Diffuser: Numerical Study Toward Active Separation Control",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aerospace Systems, Operations and Life Cycle",
"note": "\u00a9 2003 by Takao Suzuki and Tim Colonius. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. \n\nPublished Online: 11 Nov 2012. \n\nThe DNS code was developed in collaboration with Dr. S. Pirozzoli and Mr. J. Fung. The authors also would like to thank Drs. D. MacMartin, J. Paduano, T. P. Hynes, and Profs. A. P. Dowling, R. Murray, A. Leonard, and H. Nagib for fruitful discussions. This research was sponsored by the DARPA (Defense Advanced Research Project Agency) program (the contract number F49620-00-C-0035).\n\nSubmitted - SuzukiColonius2003a.pdf
",
"abstract": "We develop a reduced order model for large-scale unsteadiness (vortex shedding) in a two-dimensional diffuser and study the mechanisms of active flow separation control. This model can estimate the vortex shedding frequency for inviscid flows by accounting for the accumulated vorticity flux in the diffuser. The model can also predict the stagnation pressure loss, which consists of two parts: A steady part corresponds to static pressure loss on the detached area, and an unsteady part is associated with vortex shedding. To validate this model, we perform direct numerical simulation (DNS) of compressible, laminar diffuser flows. The comparison between the model and DNS shows good agreement at various Mach numbers and area ratios of the diffuser in terms of vortex shedding time scale and stagnation pressure loss. To investigate the effects of periodic mass injection near the separation point, we also perform DNS over a wide range of the forcing frequency. The DNS results show that periodic mass injection can pinch off vortices with a smaller size; accordingly, their convective velocity is increased, absorption of circulation from the wall is enhanced, and the extent of the separated region is reduced. As a result, the stagnation pressure recovery, particularly the unsteady part, is substantially improved as predicted by the model.",
"date": "2003-01",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190718-165127428",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190718-165127428",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Defense Advanced Research Projects Agency (DARPA)",
"grant_number": "F49620-00-C-0035"
}
]
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"id": "2003-1138",
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{
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{
"id": "Bertolotti-F-P",
"name": {
"family": "Bertolotti",
"given": "Fabio P."
}
},
{
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}
]
},
"title": "On the Noise Generated by Shear-Layer Instabilities in Turbulent Jets",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aerospace Systems, Operations and Life Cycle",
"note": "\u00a9 2003 by United Technologies Corporation. Published by the American Institute of Aeronautics and Astronautics, Inc. with permission. \n\nPublished Online: 11 Nov 2012.\n\nPublished - BertolottiColonius2003.pdf
",
"abstract": "Solutions to the linearized equations of motion are used to study sound radiation by convected disturbances in the jet core. The spectrum of eigenmodes reveals the presence of modes that represent convected vortical and entropic motions in the potential core of the jet. We investigate the near-field acoustics produced by these core modes using the Parabolozied Stability Equations. At the conditions of commercial jet engines during take-off, the core modes radiate sound effectively along Mach lines due to the jet centerline velocity being supersonic relative to the fee-stream speed of sound. Summing three of these modes to create two distinct disturbances - one that is velocity dominated, and another that is entropy dominated - one observes that entropy variations radiate sound more effectively than vortical variations. \n\nThe results yield a first insight into the impact of large-scale mixing inhomogeneities on the acoustic field. Such disturbances are created by devices in the jet engine itself, such as flow mixers, turbine exit vanes, and combustion-chamber (i.e. pattern factors).",
"date": "2003-01",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190718-165125289",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190718-165125289",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
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"id": "2003-1062",
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"doi": "10.2514/6.2003-1062",
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{
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}
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},
"title": "Numerical Simulation of Shock and Bubble Dynamics in Shockwave Lithotripsy",
"ispublished": "unpub",
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"note": "\u00a9 2002 Acoustical Society of America. \n\nPublished Online: 25 October 2002. \n\nWork supported by NIH P01 DK\u201043881 and NSF under grant CTS\u20109979258.",
"abstract": "Theoretical evaluation of the efficacy of stone comminution (and potential for tissue damage) during shockwave lithotripsy requires knowledge of the complex stress fields associated with both the incident focussing shock and the dynamics of cavitation bubbles that it induces. While simple models from geometrical acoustics and subsequent modeling of spherical bubbles in isolation (Gilmore equation) can provide estimates, high\u2010speed photography in vitro reveals a far more complex flow with bubble number densities that are sufficiently high such that collective effects associated with a cloud of bubbles are important. This talk will describe a modeling effort aimed at estimating stresses from these complex lithotripter generated flow fields. We compute the time\u2010dependent, compressible, ensemble\u2010averaged two\u2010phase flow equations with a finite\u2010difference scheme. Detailed modeling of the dynamics of bubbles (on the microscale) and high\u2010order weighted essentially nonoscillatory shock\u2010capturing schemes are employed. The model is compared to hydrophone and passive cavitation detection measurements, as well as qualitative comparison with high\u2010speed photography. Finally, we explore collective bubble mechanisms ranging from defocusing and shielding of the stone (for high bubble densities in the focal region) to enhanced stresses due to concerted cloud collapse in a dual\u2010pulse lithotripsy configuration.",
"date": "2002-10-25",
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"id_number": "CaltechAUTHORS:20190709-092059532",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092059532",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "NIH",
"grant_number": "P01 DK\u201043881"
},
{
"agency": "NSF",
"grant_number": "CTS\u20109979258"
}
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},
"doi": "10.1121/1.4779204",
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"items": [
{
"id": "Rowley-C-W",
"name": {
"family": "Rowley",
"given": "Clarence W."
},
"orcid": "0000-0002-9099-5739"
},
{
"id": "Williams-D-R",
"name": {
"family": "Williams",
"given": "David R."
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Murray-R-M",
"name": {
"family": "Murray",
"given": "Richard M."
},
"orcid": "0000-0002-5785-7481"
},
{
"id": "MacMartin-D-G",
"name": {
"family": "MacMartin",
"given": "Douglas G."
},
"orcid": "0000-0003-1987-9417"
},
{
"id": "Fabris-Drazin",
"name": {
"family": "Fabris",
"given": "Drazin"
}
}
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},
"title": "Model-based control of cavity oscillations. II - System identification and analysis",
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"full_text_status": "public",
"keywords": "Aerospace Systems, Operations and Life Cycle",
"note": "\u00a9 2001 by the authors. Published by the American Institute of Aeronautics and Astronautics, Inc. with permission. \n\nWe would like to thank Andrzej Banaszuk for many helpful comments, and for suggesting the method for distinguishing between stable and unstable noisy systems. The theoretical work was supported by AFOSR under grant F49620-98-1-0095 with program manager Dr. Thomas Beutner. The experimental work was supported by AFOSR under grant F49620-98-1-0276, with program manager Dr. Steve Walker.\n\nPublished - RowleyWilliamsColoniusEtAl2002.pdf
",
"abstract": "Experiments using active control to reduce oscillations in the flow past a rectangular cavity have uncovered surprising phenomena: in the controlled system, often new frequencies of oscillation appear, and often the main frequency of oscillation is split into two sideband frequencies. The goal of this paper is to explain these effects using physics-based models, and to use these ideas to guide control design.\n\nWe present a linear model for the cavity flow, based on the physical mechanisms of the familiar Rossiter model. Experimental data indicates that under many operating conditions, the oscillations are not self-sustained, but in fact are caused by amplification of external disturbances. We present some experimental results demonstrating the peak-splitting phenomena mentioned above, use the physics-based model to study the phenomena, and discuss fundamental performance limitations which limit the achievable performance of any control scheme.",
"date": "2002-08-22",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190709-092100972",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092100972",
"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": "F49620-98-1-0095"
},
{
"agency": "Air Force Office of Scientific Research (AFOSR)",
"grant_number": "F49620-98-1-0276"
}
]
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"creators": {
"items": [
{
"id": "Colonius-T",
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},
{
"id": "Freund-J-B",
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"given": "J. B."
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}
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},
"title": "POD Analysis of Sound Generation by a Turbulent Jet",
"ispublished": "unpub",
"full_text_status": "public",
"note": "\u00a9 2002 by J. B. Freund. Published by the American Institute of Aeronautics and Astronautics, Inc. with permission. \n\nPublished Online: 22 Aug 2012. \n\nJBF gratefully acknowledges the support of NASA. Both authors acknowledge fruitful interactions with Dr. Peter Blossey whose initial computations of pressure POD modes from this database inspired the present effort.\n\nPublished - ColoniusFreund2002.pdf
",
"abstract": "A Proper Orthogonal Decomposition (POD) is constructed for a Mach 0.9 turbulent jet using a well-validated direct numerical simulation database. Norms are defined based on near-field volume integrals of pressure, turbulence kinetic energy, streamwise velocity, and total enthalpy, two-dimensional integrals of streamswise velocity (to match experimental measurements), and far-field integrals of pressure over a sphere. We find substantially different POD modes for the different norms, and their efficiency at representing the full data is strongly dependent upon the norm and specifically which data we attempt to represent. To reproduce near-field turbulence statistics requires relatively few modes computed by a kinetic energy or pressure norm. However, a large number of the POD modes computed using a near-field norm are required to represent the sound field. The dominant near-field POD modes computed with either the near-field pressure norm or the sound field norm have the structure of wave packets.",
"date": "2002-08-22",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190709-092059690",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092059690",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "NASA"
}
]
},
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"items": [
{
"id": "Preston-A-T",
"name": {
"family": "Preston",
"given": "A."
}
},
{
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"name": {
"family": "Colonius",
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},
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},
{
"id": "Brennen-C-E",
"name": {
"family": "Brennen",
"given": "C. E."
}
}
]
},
"title": "A Reduced-Order Model of Heat Transfer Effects on the Dynamics of Bubbles",
"ispublished": "unpub",
"full_text_status": "public",
"note": "Published - PRE215.pdf
",
"abstract": "The Rayleigh-Plesset equation has been used extensively to model spherical bubble dynamics, yet it has been shown that it cannot correctly capture damping effects due to mass and thermal diffusion. Radial diffusion equations may be solved for a single bubble, but these are too computationally expensive to implement into a continuum model for bubbly cavitating flows since the diffusion equations must be solved at each position in the flow. The goal of the present research is to derive reduced-order models that account for thermal and mass diffusion. We present a model that can capture the damping effects of the diffusion processes in two ODE's, and gives better results than previous models.",
"date": "2002-07-14",
"date_type": "published",
"publisher": "Caltech Library",
"id_number": "CaltechAUTHORS:PREfedsm02",
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"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
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"author_list": "Preston, A.; Colonius, T.; et el."
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"items": [
{
"id": "Pishchalnikov-Y-A",
"name": {
"family": "Pishchalnikov",
"given": "Yuriy A."
}
},
{
"id": "Sapozhnikov-O-A",
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"family": "Sapozhnikov",
"given": "Oleg A."
}
},
{
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"family": "Williams",
"given": "James C."
}
},
{
"id": "Evan-A-P",
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"family": "Evan",
"given": "Andrew P."
}
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{
"id": "McAteer-J-A",
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},
{
"id": "Crum-L-A",
"name": {
"family": "Crum",
"given": "Lawrence A."
}
}
]
},
"title": "Cavitation bubble cluster activity in the breakage of stones by shock wave lithotripsy",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Optical imaging; Organs; Cavitation bubbles; Medical diagnosis",
"note": "\u00a9 2002 Acoustical Society of America. \n\nPublished Online: 06 May 2002. \n\nWork supported by NIH DK43881.",
"abstract": "High\u2010speed photography was used to investigate cavitation at the surface of artificial and natural kidney stones during exposure to lithotripter shock pulses in vitro. It was observed that numerous individual bubbles formed over virtually the entire surface of the stone, but these bubbles did not remain independent and combined with one another to form larger bubbles and bubble clusters. The movement of bubble boundaries across the surface left portions of the stone bubble free. The biggest cluster grew to envelop the proximal end of the stone (6.5 mm diameter artificial stone) then collapsed to a small spot that over multiple shots formed a crater in that face of the stone. The bubble clusters that developed at the sides of stones tended to align along fractures and to collapse into these cracks. High\u2010speed camera images demonstrated that cavitation\u2010mediated damage to stones was due not to the action of solitary, individual bubbles, but to the forceful collapse of dynamic clusters of bubbles.",
"date": "2002-05-06",
"date_type": "published",
"id_number": "CaltechAUTHORS:20190709-092102208",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190709-092102208",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "NIH",
"grant_number": "DK43881"
}
]
},
"doi": "10.1121/1.4778494",
"resource_type": "conference_item",
"pub_year": "2002",
"author_list": "Pishchalnikov, Yuriy A.; Sapozhnikov, Oleg A.; et el."
},
{
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"items": [
{
"id": "Williams-D-R",
"name": {
"family": "Williams",
"given": "David R."
}
},
{
"id": "Rowley-C-W",
"name": {
"family": "Rowley",
"given": "Clarence W."
},
"orcid": "0000-0002-9099-5739"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Murray-R-M",
"name": {
"family": "Murray",
"given": "Richard M."
},
"orcid": "0000-0002-5785-7481"
},
{
"id": "MacMartin-D-G",
"name": {
"family": "MacMartin",
"given": "Douglas G."
},
"orcid": "0000-0003-1987-9417"
},
{
"id": "Fabris-Drazin",
"name": {
"family": "Fabris",
"given": "Drazin"
}
},
{
"id": "Albertson-Julie",
"name": {
"family": "Albertson",
"given": "Julie"
}
}
]
},
"title": "Model-based control of cavity oscillations. I - Experiments",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aerospace Systems, Operations and Life Cycle",
"note": "\u00a9 2002 by David R. Williams. Published by the American Institute of Aeronautics and Astronautics, Inc. with permission. \n\nPublished Online: 22 Aug 2012. \n\nWe are grateful for the support provided by the Air Force Office of Scientific Research through contract F49620-98-1-0276. The program was managed by Dr. Steven Walker. Actuator development at IIT was done by Mr. Byung-Hun Kim with partial support from the Aerospace Illinois: a NASA Space Grant Consortium. A special thanks goes to Mr. Ken Ostasiewski, Mr. Tim Hayden and SSgt. Buddy Johns for their invaluable assistance during the experiments over the last three years.\n\nPublished - WilliamsRowleyColoniusEtAl2002.pdf
",
"abstract": "An experimental investigation of acoustic mode noise suppression was conducted in a cavity using a digital controller with a linear control algorithm. The control algorithm was based on flow field physics similar to the Rossiter model for acoustic resonance. Details of the controller and results from its implementation are presented in the companion paper by Rowley, et al.\n\nHere the experiments and some details of the flow field development are described, which were done primarily at Mach number 0.34 corresponding to single mode resonance in the cavity. A novel method using feedback control to suppress the resonant mode and open-loop forcing to inject a non-resonant mode was developed for system identification. The results were used to obtain empirical transfer functions of the components of resonance, and measurements of the shear layer growth for use in the design of the control algorithm.",
"date": "2002-01",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190718-165126408",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190718-165126408",
"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": "F49620-98-1-0276"
},
{
"agency": "Illinois Space Grant Consortium"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2002-0971",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2002-971",
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"pub_year": "2002",
"author_list": "Williams, David R.; Rowley, Clarence W.; et el."
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{
"id": "Theofilis-V",
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"family": "Theofilis",
"given": "V."
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},
{
"id": "Sherwin-S-J",
"name": {
"family": "Sherwin",
"given": "S. J."
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "T."
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "A unifying perspective of linear flow instabilities",
"ispublished": "unpub",
"full_text_status": "public",
"date": "2002",
"date_type": "published",
"publisher": "Caltech Library",
"id_number": "CaltechAUTHORS:20190718-165126719",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190718-165126719",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"resource_type": "conference_item",
"pub_year": "2002",
"author_list": "Theofilis, V.; Sherwin, S. J.; et el."
},
{
"id": "https://authors.library.caltech.edu/records/3y6g3-xxv50",
"eprint_id": 97454,
"eprint_status": "archive",
"datestamp": "2023-08-19 07:51:38",
"lastmod": "2023-10-18 15:57:36",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Eldredge-J-D",
"name": {
"family": "Eldredge",
"given": "Jeff"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Leonard-A",
"name": {
"family": "Leonard",
"given": "Anthony"
}
}
]
},
"title": "A Vortex Particle Method for Compressible Flows",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Computational Fluid Dynamics",
"note": "\u00a9 2001 by the authors. Published by the American Institute of Aeronautics and Astronautics, Inc. with permission. \n\nPublished Online: 22 Aug 2012. \n\nThe first author gratefully acknowledges support from a Graduate Research Fellowship from the National Science Foundation.\n\nPublished - EldredgeColoniusLeonard2001.pdf
",
"abstract": "A vortex particle method for the simulation of two-dimensional compressible flows is developed. The computational elements are Lagrangian particles that carry vorticity,dilatation,enthalpy,entropy and density. The velocity field is decomposed into irrotational and solenoidal parts,which allows its calculation in terms of the particles' vorticity and dilatation. The particle coverage is truncated and incident acoustic waves are absorbed using a suitable boundary treatment. A Kirchhoff surface formulation is developed for computing the far-field sound. The method is applied to a co-rotating vortex pair and the results are discussed.",
"date": "2001-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190726-104729692",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190726-104729692",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "NSF Graduate Research Fellowship"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2001-2641",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2001-2641",
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"basename": "EldredgeColoniusLeonard2001.pdf",
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"author_list": "Eldredge, Jeff; Colonius, Tim; et el."
},
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"datestamp": "2023-08-21 22:16:39",
"lastmod": "2023-10-13 20:28:06",
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"creators": {
"items": [
{
"id": "Preston-A-T",
"name": {
"family": "Preston",
"given": "Al"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Brennen-C-E",
"name": {
"family": "Brennen",
"given": "Christopher E."
}
}
]
},
"title": "Toward Efficient Computation of Heat and Mass Transfer Effects in the Continuum Model for Bubbly Cavitating Flows",
"ispublished": "unpub",
"full_text_status": "public",
"note": "Published - PRE202.pdf
",
"abstract": "The Rayleigh-Plesset equation is used extensively to model spherical bubble dynamics, yet is has been shown that it cannot correctly capture damping effects due to mass and thermal diffusion. Full single bubble models have been successfully used to study these diffusion effects, but these are to computationally expensive to implement into the continuum model for bubbly cavitating flow since the diffusion equations must be solved in the radial direction at each position in the flow. The focus of the present research is the development of simpler and more efficient bubbly dynamic models that capture the important aspects of the diffusion processes. We present some preliminary results from a full bubbly model that has been developed to provide insight into possible simplifications. This in turn can be used to develop and validate simpler models. The full model is contrasted to the Rayleigh-Plesset equations, and a suggestion for possible improvement to the Rayleigh-Plesset equation is made.",
"date": "2001-06",
"date_type": "published",
"publisher": "Caltech Library",
"id_number": "CaltechAUTHORS:PREcav01",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:PREcav01",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"primary_object": {
"basename": "PRE202.pdf",
"url": "https://authors.library.caltech.edu/records/rs2a0-agd96/files/PRE202.pdf"
},
"resource_type": "conference_item",
"pub_year": "2001",
"author_list": "Preston, Al; Colonius, Tim; et el."
},
{
"id": "https://authors.library.caltech.edu/records/trj71-n4y75",
"eprint_id": 97445,
"eprint_status": "archive",
"datestamp": "2023-08-21 22:12:21",
"lastmod": "2023-10-18 15:57:10",
"type": "conference_item",
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"creators": {
"items": [
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Computation of the Sources of Sound in Turbulent Flow",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Acoustic phenomena; Aeroacoustics; Turbulent flows",
"note": "\u00a9 2001 Acoustical Society of America. \n\nPublished Online: 05 June 2001.",
"abstract": "Direct numerical simulations of turbulent flows and their radiated acoustic fields offer a detailed description of the acoustic sources at low Reynolds number. High Reynolds number jets will remain inaccessible to direct computation for many years to come and there is thus a great need for good models of the acoustic sources. The low Reynolds number simulations can provide insight and data for such source modeling efforts. In this brief survey of research in this area issues that were anticipated in the research of Professor David Crighton for whom this session has been dedicated are discussed. These include the technical challenges that must be overcome in order to accurately compute aeroacoustic flows the modeling of acoustic sources in jets and mixing layers as wave packets and the scattering and refraction of sound by turbulence.",
"date": "2001-05",
"date_type": "published",
"id_number": "CaltechAUTHORS:20190726-104728798",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190726-104728798",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"doi": "10.1121/1.4744852",
"resource_type": "conference_item",
"pub_year": "2001",
"author_list": "Colonius, Tim"
},
{
"id": "https://authors.library.caltech.edu/records/476q0-75d28",
"eprint_id": 97470,
"eprint_status": "archive",
"datestamp": "2023-08-19 07:40:42",
"lastmod": "2023-10-18 15:58:09",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Rowley-C-W",
"name": {
"family": "Rowley",
"given": "Clarence W."
},
"orcid": "0000-0002-9099-5739"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Murray-R-M",
"name": {
"family": "Murray",
"given": "Richard M."
},
"orcid": "0000-0002-5785-7481"
}
]
},
"title": "Dynamical models for control of cavity oscillations",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 2001 by the authors. Published by the American Institute of Aeronautics and Astronautics, Inc. with permission. \n\nPublished Online: 22 Aug 2012. \n\nThis work was supported by AFOSR under grants F49620-98-1-0095 and F49620-95-1-0419. The first author gratefully acknowledges a NSF graduate research fellowship.\n\nPublished - RowleyColoniusMurray2001.pdf
",
"abstract": "We investigate nonlinear dynamical models for self-sustained oscillations in the flow past a rectangular cavity. The models are based on the method of Proper Orthogonal Decomposition (POD) and Galerkin projection, and we introduce an inner product and formulation of the equations of motion which enables one to use vector-valued POD modes for compressible flows. We obtain models between 3 and 20 states, which accurately describe both the short-time and long-time dynamics. This is a substantial improvement over previous models based on scalar-valued POD modes, which capture the dynamics for short time, but deviate for long time.",
"date": "2001-05",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190726-104731145",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190726-104731145",
"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": "F49620-98-1-0095"
},
{
"agency": "Air Force Office of Scientific Research (AFOSR)",
"grant_number": "F49620-95-1-0419"
},
{
"agency": "NSF Graduate Research Fellowship"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2001-2126",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2001-2126",
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"basename": "RowleyColoniusMurray2001.pdf",
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"resource_type": "conference_item",
"pub_year": "2001",
"author_list": "Rowley, Clarence W.; Colonius, Tim; et el."
},
{
"id": "https://authors.library.caltech.edu/records/vvney-2rv11",
"eprint_id": 97464,
"eprint_status": "archive",
"datestamp": "2023-08-19 07:09:17",
"lastmod": "2023-10-18 15:57:58",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "An overview of simulation, modeling, and active control of flow/acoustic resonance in open cavities",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aerospace Systems, Operations and Life Cycle",
"note": "\u00a9 2001 by the authors. Published by the American Institute of Aeronautics and Astronautics, Inc. with permission. \n\nPublished Online: 22 Aug 2012. \n\nI am grateful to my collaborators at Caltech, Mr. Clancy Rowley, Dr. Amit Basu, and Prof. Richard Murray, for their contributions to the cavity flow project. Thanks are due to Clancy as well for reading a draft of this report. I have also benefited from numerous discussions on cavity acoustics with A. Cain,M. Gharib, A. Roshko, D. Williams. The support by AFOSR under grant F49620-98-1-0095 with technical monitor Dr. Thomas Beutner is gratefully acknowledged.\n\nPublished - Colonius2001a.pdf
",
"abstract": "An overview of some recent advances in simulation, modeling, and control of flow/acoustic resonance in flows over open cavities is provided. A wide variety of experiments utilizing differing actuator concepts, with both open and closed-loop control, have shown that significant attenuation of tones and broadband noise is possible. These are discussed in connection with recent advances in theoretical modeling and numerical simulation. Such work may ultimately provide accurate low-order models of cavity resonance that are suitable for robust and effective control over a wide range of flow conditions. Several areas that will require further advances in our understanding of the flow physics are highlighted.",
"date": "2001-01",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190726-104730673",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190726-104730673",
"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": "F49620-98-1-0095"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2001-0076",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2001-76",
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"pub_year": "2001",
"author_list": "Colonius, Tim"
},
{
"id": "https://authors.library.caltech.edu/records/57se5-p6j06",
"eprint_id": 97474,
"eprint_status": "archive",
"datestamp": "2023-08-19 07:09:22",
"lastmod": "2023-10-18 15:58:18",
"type": "conference_item",
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"creators": {
"items": [
{
"id": "Mohseni-K",
"name": {
"family": "Mohseni",
"given": "Kamran"
},
"orcid": "0000-0002-1382-221X"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Freund-J-B",
"name": {
"family": "Freund",
"given": "Jonathan B."
}
}
]
},
"title": "On the Role of Nonlinearity in Mach Wave Radiation in a Mach = 1.92 Jet",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aerospace Systems, Operations and Life Cycle",
"note": "\u00a9 2000 by authors. Published by the American Institute of Aeronautics and Astronautics, Inc. with permission. \n\nPublished Online: 22 Aug 2012.\n\nPublished - MohseniColoniusFreund2001.pdf
",
"abstract": "Mach wave radiation in a turbulent fully expanded supersonic jet is revisited. Our goal is to determine the extent to which predictions for the radiated sound that are based on linearized analysis agree with solution of the full nonlinear equations. To this end, we solve the linearized Navier-Stokes equations (LNS) with precisely the same mean flow and inflow disturbances as a previous direct numerical simulation (DNS) of a turbulent M = 1.92 jet.1 We restrict our attention to the first two azimuthal modes, n = 0 and n = 1, which constitute most of the acoustic field. The direction of peak radiation and the peak Strouhal number matches the DNS reasonably well, which is in accord with previous experimental justification of the linear theory. However, it is found that the sound pressure level predicted by LNS is significantly lower than that from DNS. Thus, linear theory misses a substantial component of the noise. In order to investigate the discrepancy, the behavior of individual frequency components of the solution are examined. Near the peak Strouhal number, particularly for the azimuthal mode n = 1, the amplification of disturbances in the LNS closely matches those from the DNS data. However, away from the peak frequency (and generally for the azimuthal mode n = 0), the DNS data shows amplification rates roughly comparable to those at the peak Strouhal number, while those from the linear computations are damped.",
"date": "2001-01",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190726-104731478",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190726-104731478",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"other_numbering_system": {
"items": [
{
"id": "2001-0377",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.2001-377",
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},
"resource_type": "conference_item",
"pub_year": "2001",
"author_list": "Mohseni, Kamran; Colonius, Tim; et el."
},
{
"id": "https://authors.library.caltech.edu/records/vwmha-e2379",
"eprint_id": 136,
"eprint_status": "archive",
"datestamp": "2023-08-21 20:48:17",
"lastmod": "2023-10-13 20:28:04",
"type": "conference_item",
"metadata_visibility": "show",
"creators": {
"items": [
{
"id": "Preston-A-T",
"name": {
"family": "Preston",
"given": "Al"
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Brennen-C-E",
"name": {
"family": "Brennen",
"given": "Christopher E."
}
}
]
},
"title": "A Numerical Investigation of Unsteady Bubbly Cavitating Nozzle Flows",
"ispublished": "unpub",
"full_text_status": "public",
"note": "Published - PRE198.pdf
",
"abstract": "The effects of unsteady bubble dynamics on cavitating flow through a converging-diverging nozzle are investigated numerically. A continuum model that couples the Rayleigh-Plesset equation with the continuity and momentum equations is used to formulate unsteady, quasi-one-dimensional partial differential equations. These equations are solved numerically using a Lagrangian finite volume method. Special formulations are used at the boundary cells to allow Eulerian boundary conditions to be specified. Flow regimes studied include those where steady state solutions exist, and those where steady state solutions diverge at the so-called flashing instability. These latter flows consist of unsteady bubbly shock waves travelling downstream in the diverging section of the nozzle. The computations show reasonable agreement with an experiment that measures the spatial variation of pressure, velocity and void fraction for steady shockfree flows, and good agreement with an experiment that measures the shock position and throat pressure for flows with bubbly shocks.",
"date": "2000-06",
"date_type": "published",
"publisher": "Caltech Library",
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"basename": "PRE198.pdf",
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"author_list": "Preston, Al; Colonius, Tim; et el."
},
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{
"id": "Rowley-C-W",
"name": {
"family": "Rowley",
"given": "Clarence W."
},
"orcid": "0000-0002-9099-5739"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
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},
{
"id": "Murray-R-M",
"name": {
"family": "Murray",
"given": "Richard M."
},
"orcid": "0000-0002-5785-7481"
}
]
},
"title": "POD Based Models of Self-Sustained Oscillations in the Flow Past an Open Cavity",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 2000 by the authors. Published by the American Institute of Aeronautics and Astronautics, Inc. with permission. \n\nPublished Online: 22 Aug 2012. \n\nSupported by AFOSR under grant F49620-98-1-0095 with technical monitor Dr. Thomas Beutner.\n\nPublished - RowleyColoniusMurray2000.pdf
",
"abstract": "The goal of this work is to provide accurate dynamical models of oscillations in the flow past a rectangular cavity, for the purpose of bifurcation analysis and control. We have performed an extensive set of direct numerical simulations which provide the data used to derive and evaluate the models. Based on the method of Proper Orthogonal Decomposition (POD) and Galerkin projection, we obtain low-order models (from 6 to 60 states) which capture the dynamics very accurately over a few periods of oscillation, but deviate for long time.",
"date": "2000-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190726-104731320",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190726-104731320",
"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": "F49620-98-1-0095"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "2000-1969",
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"author_list": "Rowley, Clarence W.; Colonius, Tim; et el."
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"items": [
{
"id": "Colonius-T",
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"family": "Colonius",
"given": "Tim"
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},
{
"id": "Basu-A-J",
"name": {
"family": "Basu",
"given": "Amit J."
}
},
{
"id": "Rowley-C-W",
"name": {
"family": "Rowley",
"given": "Clarence W."
},
"orcid": "0000-0002-9099-5739"
}
]
},
"title": "Numerical investigation of the flow past a cavity",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 1999 by the authors. Published by the American Institute of Aeronautics and Astronautics, Inc. with permission. \n\nPublished Online: 22 Aug 2012. \n\nThis research was supported by AFOSR under grant F49620-98-1-0095 with technical monitor Dr. Thomas Beutner. Supercomputer time was provided by the Department of Defense High Performance Computing centers, as well as the National Science Foundation. C.W. Rowley acknowledges the support of a National Science Foundation Graduate Fellowship.\n\nPublished - ColoniusBasuRowley1999.pdf
",
"abstract": "Numerical simulations are used to investigate the resonant instabilities in the flow past an open cavity. The compressible Navier-Stokes equations are solved directly (no turbulence model) for two-dimensional cavities with laminar boundary layers upstream. The computational domain is large enough to directly resolve a portion of the radiated acoustic field. The results show a transition from a shear layer mode, for shorter cavities and lower Mach numbers, to a wake mode for longer cavities and higher Mach numbers. The shear layer mode is well characterized by Rossiter modes. The wake mode is characterized instead by a large-scale vortex shedding with Strouhal number independent of the Mach number. The vortex shedding causes the boundary layer to periodically separate upstream of the cavity. The wake mode oscillation is similar to that reported by Gharib and Roshko (J. Fluid Mech., 177, 1987) for incompressible ow with a laminar upstream boundary layer. The results suggest that laminar separation upstream of the cavity edge is the cause of the transition to wake mode.",
"date": "1999-05",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190726-104730595",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190726-104730595",
"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": "F49620-98-1-0095"
},
{
"agency": "NSF Graduate Research Fellowship"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "99-1912",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.1999-1912",
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"pub_year": "1999",
"author_list": "Colonius, Tim; Basu, Amit J.; et el."
},
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"datestamp": "2023-08-22 13:31:10",
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"items": [
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"id": "Colonius-T",
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]
},
"title": "Direct numerical simulation of sound generation in turbulent shear flows",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Fluid flows; Linear stability analysis; Supersonics; Computational fluid dynamics; Acoustic phenomena; Supersonic jets; Acoustic field; Acoustic analogies; Subsonic flows; Sound generation",
"note": "\u00a9 1999 Acoustical Society of America. \n\nPublished Online: 25 January 1999. \n\nWork supported by NSF (CTS\u20109501349) and AFOSR (F49620\u201098\u20101\u20100095).",
"abstract": "Direct numerical simulations of turbulent shear flows and their radiated acoustic fields have provided new insights into the mechanisms of sound generation, as well as the efficacy and limitations of the acoustic analogy approach. At present, these computations are expensive, and limited to relatively low Reynolds number and canonical flows. The computational approach consists of using high\u2010order accurate numerical methods, together with accurate and robust nonreflecting and buffer\u2010zone boundary conditions. This talk will focus on the results of computations of sound generated in mixing layers, jets, and open cavity flows. The relationship between linear stability waves in the flow and the radiated acoustic field is examined, in the context of a forced subsonic mixing layer and a fully turbulent supersonic round jet. For the subsonic flow, the acoustic sources can be modeled as wave packets, which radiate a superdirective acoustic field. For the supersonic jet, the directly computed (i.e., nonlinear source) acoustic field is compared to predictions based on radiating stability waves. Finally, the flow/acoustic instabilities in the subsonic flow over an open cavity are examined, and control strategies for reducing the internal acoustic load are explored.",
"date": "1999-01-25",
"date_type": "published",
"id_number": "CaltechAUTHORS:20190726-104730754",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190726-104730754",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "NSF",
"grant_number": "CTS\u20109501349"
},
{
"agency": "Air Force Office of Scientific Research (AFOSR)",
"grant_number": "F49620\u201098\u20101\u20100095"
}
]
},
"doi": "10.1121/1.425824",
"resource_type": "conference_item",
"pub_year": "1999",
"author_list": "Colonius, Tim"
},
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"creators": {
"items": [
{
"id": "Rowley-C-W",
"name": {
"family": "Rowley",
"given": "Clarence W."
},
"orcid": "0000-0002-9099-5739"
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
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}
]
},
"title": "Numerically nonreflecting boundary conditions for multidimensional aeroacoustic computations",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 1998 by Clarence W. Rowley and Tim Colonius. Published by the Confederation of European Aerospace Societies, with permission. \n\nPublished Online: 22 Aug 2012. \n\nThis research was supported in part by the National Science Foundation under grant CTS-9501349 with technical monitor Dr. Roger Arndt, and we also acknowledge the recent support of AFOSR under grant F49620-98-1-0095 with technical monitor Dr. Mark Glauser.\n\nPublished - RowleyColonius1998.pdf
",
"abstract": "Many compressible flow and aeroacoustic computations rely on accurate nonreflecting or radiation boundary conditions. When the equations and boundary conditions are discretized using a finite- difference scheme, the dispersive nature of the discretized equations can lead to spurious numerical reflections not seen in the continuous boundary value problem. These reflections can lead to poor convergence to a stationary state, and can lead to self-forcing of flows. We have constructed numerically nonreflecting boundary conditions which account for the particular finite-difference scheme used, and are designed to minimize these spurious numerical reflections. These extend our earlier work on one- dimensional boundary conditions to the multidimensional case. Stable boundary conditions which are nonreflecting to arbitrarily high-order-of-accuracy are obtained. Various test cases are presented which show excellent results.",
"date": "1998-06",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190726-104731244",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190726-104731244",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "NSF",
"grant_number": "CTS-9501349"
},
{
"agency": "Air Force Office of Scientific Research (AFOSR)",
"grant_number": "F49620-98-1-0095"
}
]
},
"other_numbering_system": {
"items": [
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"id": "98-2220",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.1998-2220",
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"pub_year": "1998",
"author_list": "Rowley, Clarence W. and Colonius, Tim"
},
{
"id": "https://authors.library.caltech.edu/records/ndh7z-em264",
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"creators": {
"items": [
{
"id": "Brennen-C-E",
"name": {
"family": "Brennen",
"given": "Christopher E."
}
},
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "d'Auria-F",
"name": {
"family": "d'Auria",
"given": "Fabrizio"
}
}
]
},
"title": "Computing Shock Waves in Cloud Cavitation",
"ispublished": "unpub",
"full_text_status": "public",
"note": "This research was supported, in part, by the Office of Naval Research under grant number N00014-91-J-1295. The third author is also grateful for support from the European Space Agency.\n\nPublished - BRE182.pdf
",
"abstract": "This paper presents a numerical investigation of some of the phenomena involved in the nonlinear dynamics of a homogeneous bubbly mixture bounded by an oscillatory wall. This problem represents an idealization of the flow in a typical vibratory cavitation damage device. Results are presented showing that wave steepening and ultimately shock wave formation occur as the magnitude of the excitation increases. The propagation characteristics of the waves through the bubbly medium have also been studied. Strong pressure peaks of short duration, corresponding to the coherent collapse of the bubble clusters, are computed and accurately resolved, both in space and time. As the amplitude of the excitation is increased a series of period doubling bifurcations occurs. The nonlinear dynamics of the oscillating bubble cluster are observed to follow a subharmonic route to chaos.",
"date": "1998",
"date_type": "published",
"publisher": "Caltech Library",
"id_number": "CaltechAUTHORS:CEBcav98",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:CEBcav98",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Office of Naval Research (ONR)",
"grant_number": "N00014-91-J-1295"
},
{
"agency": "European Space Agency (ESA)"
}
]
},
"primary_object": {
"basename": "BRE182.pdf",
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"pub_year": "1998",
"author_list": "Brennen, Christopher E.; Colonius, Tim; et el."
},
{
"id": "https://authors.library.caltech.edu/records/r5sat-9t240",
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"datestamp": "2023-08-20 07:34:24",
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"creators": {
"items": [
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
}
]
},
"title": "Numerically nonreflecting boundary and interface conditions",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aeroacoustics",
"note": "\u00a9 1996 American Institute of Aeronautics and Astronautics, Inc. \n\nPublished Online: 22 Aug 2012.",
"abstract": "Accurate nonreflecting or radiation boundary conditions are important for effective computation of aeroacoustic and compressible flow problems. In the present work, exact 'discretely nonreflecting boundary closures are derived by considering a one dimensional hyperbolic equation discretized with finite difference schemes and Runge-Kutta time advancements. The current methodology leads to stable local finite-difference-like boundary closures which are nonreflecting to an essentially arbitrarily high order of accuracy. These conditions can also be applied at interfaces where there is a discontinuity in the wave speed or where there is an abrupt change in the grid spacing. compared to other boundary treatments, the present boundary and interface conditions can reduce spurious reflected energy in the computational domain by many orders of magnitude.",
"date": "1996-05",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190726-104730993",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190726-104730993",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"other_numbering_system": {
"items": [
{
"id": "96-1661",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.1996-1661",
"resource_type": "conference_item",
"pub_year": "1996",
"author_list": "Colonius, Tim"
},
{
"id": "https://authors.library.caltech.edu/records/27xtm-nzx97",
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"eprint_status": "archive",
"datestamp": "2023-08-20 03:12:15",
"lastmod": "2023-10-18 15:57:47",
"type": "conference_item",
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"creators": {
"items": [
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Lele-S-K",
"name": {
"family": "Lele",
"given": "Sanjiva K."
}
},
{
"id": "Moin-Parviz",
"name": {
"family": "Moin",
"given": "Parviz"
},
"orcid": "0000-0002-0491-7065"
}
]
},
"title": "Direct computation of the sound generated by two-dimensional shear layer",
"ispublished": "unpub",
"full_text_status": "public",
"note": "\u00a9 1993 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. \n\nPublished Online: 22 Aug 2012. \n\nThis work was supported by the Office of Naval Research. Computer time was provided by NASA Ames.\n\nPublished - ColoniusLeleMoin1993a.pdf
",
"abstract": "The sound generated by a two dimensional shear layer is investigated by Direct Numerical Simulation (DNS) of the compressible Navier-Stokes equations. A high-order-accurate numerical scheme and non-reflecting boundary conditions are used to accurately compute both the near field hydrodynamics and the acoustic waves produced by the layer. The directly computed acoustic field shows that the acoustic waves which are generated at the fundamental frequency (most unstable mode), and its first two sub-harmonics, originate near the region where the instability wave at these frequencies saturate, i.e. the region where the layer rolls up into vortices for the fundamental frequency, and the first two Vortex pairings for the sub-harmonics. The sound generated by the pairings is most intense in the downstream direction, indicating a superdirective acoustic source.",
"date": "1993-10",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190726-104730351",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190726-104730351",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Office of Naval Research (ONR)"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "93-4328",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.1993-4328",
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"basename": "ColoniusLeleMoin1993a.pdf",
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"resource_type": "conference_item",
"pub_year": "1993",
"author_list": "Colonius, Tim; Lele, Sanjiva K.; et el."
},
{
"id": "https://authors.library.caltech.edu/records/4p8y7-kyz35",
"eprint_id": 97461,
"eprint_status": "archive",
"datestamp": "2023-08-19 23:38:58",
"lastmod": "2023-10-18 15:57:50",
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"creators": {
"items": [
{
"id": "Colonius-T",
"name": {
"family": "Colonius",
"given": "Tim"
},
"orcid": "0000-0003-0326-3909"
},
{
"id": "Lele-S-K",
"name": {
"family": "Lele",
"given": "Sanjiva K."
}
},
{
"id": "Moin-Parviz",
"name": {
"family": "Moin",
"given": "Parviz"
},
"orcid": "0000-0002-0491-7065"
}
]
},
"title": "Scattering of Sound Waves by a Compressible Vortex",
"ispublished": "unpub",
"full_text_status": "public",
"keywords": "Aerospace Systems, Operations and Life Cycle",
"note": "\u00a9 1990 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. \n\nPublished Online: 17 Aug 2012. \n\nThis work was supported by the Office of Naval Research.\n\nPublished - ColoniusLeleMoin1991a.pdf
",
"abstract": "Scattering of plane sound waves by a compressible vortex is investigated by direct computation of the 2-d Navier-Stokes equations. Non-reflecting boundary conditions are utilized, and their accuracy is established by comparing results on different sized domains. Scattered waves are directly measured from the computations. The resulting amplitude and directivity pattern of the scattered waves is discussed, and compared to various theoretical predictions. For compact vortices (zero circulation), the scattered waves directly computed are in good agreement with predictions based on an acoustic analogy. Strong scattering at about \u00b130\u00b0 from the direction of incident wave propagation is observed. Back scattering is an order of magnitude smaller than forward scattering. For vortices with finite circulation refraction of the sound by the mean flow field outside the vortex core is found to be important in determining the amplitude and directivity of the scattered wave field.",
"date": "1991-01",
"date_type": "published",
"publisher": "American Institute of Aeronautics and Astronautics",
"id_number": "CaltechAUTHORS:20190726-104730425",
"official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190726-104730425",
"rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.",
"funders": {
"items": [
{
"agency": "Office of Naval Research (ONR)"
}
]
},
"other_numbering_system": {
"items": [
{
"id": "91-0494",
"name": "AIAA Paper"
}
]
},
"doi": "10.2514/6.1991-494",
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"basename": "ColoniusLeleMoin1991a.pdf",
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},
"resource_type": "conference_item",
"pub_year": "1991",
"author_list": "Colonius, Tim; Lele, Sanjiva K.; et el."
}
]