@article{varigonda_serafim_freydin_dowell_narayanaswamy_2024, title={Two-dimensional pressure field imaging of an elastic panel executing post-flutter oscillations}, volume={125}, ISSN={["1095-8622"]}, DOI={10.1016/j.jfluidstructs.2023.104056}, abstractNote={Two dimensional pressure field was acquired at 10 kHz to study the post flutter oscillations of a thin elastic panel placed beneath a Mach 2.5 turbulent boundary layer. The panel was made of aluminum and is secured to the mounting fixture using a collection of rivets, which resulted in a boundary condition that was between both ideally clamped and pinned boundaries. Direct comparison of the mean and unsteady pressure fields were made for the panel executing post flutter oscillations and oscillations away from the flutter boundary. Whereas the mean pressure fields were largely similar during and away from post-flutter oscillations, the unsteady pressure fields showed a significant increase in the pr.m.s. during post flutter oscillations. The spectral content of the pressure oscillations and panel oscillations revealed that the tonal aeroelastic frequency dominate the post flutter oscillations. This tonal frequency was determined to lie at the close vicinity of the (2,1) panel elastic mode. The r.m.s. panel deflection field during post flutter oscillations were also reconstructed from the unsteady pressure fields and the reconstructed panel deflection also corresponded to the (2,1) elastic mode.Further coherence and cross-correlation analyses provided insights into possible mechanisms that control the transition of the panel oscillations away from the flutter boundary. The analyses suggest that the transition away from the flutter boundary is possibly initiated by the decoherence of the organized pressure field during the post flutter region by the turbulent boundary layer.}, journal={JOURNAL OF FLUIDS AND STRUCTURES}, author={Varigonda, Santosh V. and Serafim, Luisa P. and Freydin, Maxim and Dowell, Earl. H. and Narayanaswamy, Venkateswaran}, year={2024}, month={Mar} }
 @article{varigonda_narayanaswamy_2023, title={Fluid structure interactions generated by an oblique shock impinging on a thin elastic panel}, volume={119}, ISSN={["1095-8622"]}, url={http://dx.doi.org/10.1016/j.jfluidstructs.2023.103890}, DOI={10.1016/j.jfluidstructs.2023.103890}, abstractNote={The flow structure coupling generated by an impinging shock boundary layer interactions (SBLI) flowfield over a rectangular panel is investigated. The impinging oblique shock is generated by an 8° shock generator placed incident to a Mach 2.5 flow. The shock strength is large enough to generate a mean separation that is nearly two-dimensional over the panel span. The panel is configured such that the panel oscillation amplitude is much smaller than the panel and incoming boundary layer thicknesses. This resulted in a weak coupling between the flowfield and structural response, and forms a relatively simpler configuration to study. Two multivariate measurement campaigns are performed to capture the mean and dynamic flowfield and panel response. The first campaign simultaneously measures the 2D panel surface pressure field, panel center-span deflection, and off-body velocity field at 10 Hz. The second campaign measures simultaneously the 2D panel surface pressure field and panel strain at two mid-span locations at 10 kHz. The acquisition rate is sufficient to resolve at least the first seven panel elastic models. These measurements provide comprehensive information about the fluid structure interaction (FSI) phenomenon from both aerodynamics and structural dynamics perspectives. Summarily, with the weak flow/structure interactions implemented in this study, there is no change in the mean separation size. However, the pressure fluctuations beneath the SBLI unit exhibit discrete elevations in the vicinity of different panel resonance mode frequencies. The greatest elevation pressure PSD occurs at the panel modes that overlaps with the separation bubble pulsation frequency band. Detailed coherence maps at and away from panel elastic modes and conditional statistics reveal critical insights into the mechanisms that cause the strengthening of the pressure fluctuations due to flow/structure coupling. It was found that the acoustic forcing by the cavity resonance has an important contribution to the dynamics of the surface pressure and panel oscillations.}, journal={JOURNAL OF FLUIDS AND STRUCTURES}, publisher={Elsevier BV}, author={Varigonda, S. V. and Narayanaswamy, V.}, year={2023}, month={May} }
 @article{freydin_dowell_varigonda_narayanaswamy_2022, title={Response of a plate with piezoelectric elements to turbulent pressure fluctuation in supersonic flow}, volume={114}, ISSN={["1095-8622"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85135818767&partnerID=MN8TOARS}, DOI={10.1016/j.jfluidstructs.2022.103696}, abstractNote={The aeroelastic response of a plate with supersonic freestream flow on one side and a shallow cavity on the other to turbulent pressure fluctuations is investigated computationally and experimentally. An empirical model is developed for the pressure fluctuations in a turbulent boundary layer that accounts for spatial and spectral variations in the pressure field. Supersonic wind tunnel tests were conducted in a Mach 2.5 flow with and without an impinging shock at the plate surface. In both cases the boundary layer was turbulent. The impinging shock creates shock-wave boundary-layer interaction, which alters the characteristics of the pressure fluctuations. Pressure-sensitive paint was used to measure the unsteady pressure on the surface of a rigid plate and characterize the pressure field (local mean, rms, and the spatial coherence length) and piezoelectric patches were used as sensors to measure the response of an elastic plate. The extracted pressure parameters were used to simulate the fluid–structure response and correlate with experiments. The computed pressure perturbation due to plate motion is found to be small relative to the natural pressure fluctuation for the fluid/structural configuration studied. Computed and measured power spectra of the piezoelectric element voltage show good agreement over a wide range of structural natural frequencies. Aeroelastic response sensitivity to pressure fluctuation coherence length was also investigated computationally. It is found that with small fluid elements, which represent small-scale uncorrelated noise, the structural response is relatively small because the excitation is filtered by the plate dynamics. Experimental results suggest that the effective excitation spatial scale is on the order of the boundary layer thickness.}, journal={JOURNAL OF FLUIDS AND STRUCTURES}, author={Freydin, Maxim and Dowell, Earl H. and Varigonda, Santosh Vaibhav and Narayanaswamy, Venkateswaran}, year={2022}, month={Oct} }
 @article{varigonda_narayanaswamy_2021, title={Methodology to image the panel surface pressure power spectra in weakly coupled fluid/structure interactions}, volume={62}, ISSN={["1432-1114"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85117895242&partnerID=MN8TOARS}, DOI={10.1007/s00348-021-03314-4}, number={11}, journal={EXPERIMENTS IN FLUIDS}, author={Varigonda, S. V. and Narayanaswamy, V.}, year={2021}, month={Nov} }
 @article{freydin_levin_dowell_varigonda_narayanaswamy_2021, title={Natural Frequencies of a Heated Plate: Theory and Experiment (Sept, 10.2514/1.J059660, 2020)}, volume={59}, ISSN={["1533-385X"]}, DOI={10.2514/1.J059660.c1}, abstractNote={Free AccessArticle UpdatesCorrection: Natural Frequencies of a Heated Plate: Theory and ExperimentCorrections for this articleNatural Frequencies of a Heated Plate: Theory and ExperimentMaxim Freydin, Dani Levin, Earl H. Dowell, Santosh Vaibhav Varigonda and Venkateswaran NarayanaswamyMaxim Freydin https://orcid.org/0000-0001-5146-0216 Duke University, Durham, North Carolina 27708Search for more papers by this author, Dani Levin Duke University, Durham, North Carolina 27708Search for more papers by this author, Earl H. Dowell Duke University, Durham, North Carolina 27708Search for more papers by this author, Santosh Vaibhav Varigonda North Carolina State University, Raleigh, North Carolina 27695Search for more papers by this author and Venkateswaran Narayanaswamy North Carolina State University, Raleigh, North Carolina 27695Search for more papers by this authorPublished Online:7 May 2021https://doi.org/10.2514/1.J059660.c1SectionsRead Now ToolsAdd to favoritesDownload citationTrack citations ShareShare onFacebookTwitterLinked InRedditEmail AboutCorrection NoticeThis correction pertains to the numerical values of the non-dimensional in-plane edge stiffness presented in the results section in the original article when it was first published online [https://doi.org/10.2514/1.J059660]. The error originates in an erroneous mathematical definition made in a separate paper [6] in which the structural plate model with elastic in-plane boundaries was derived. The error resulted in a respective error in the numerical code. The effect of that error on the results in this article is that all numerical values of the non-dimensional in-plane edge stiffness stated throughout the paper need to be multiplied by a factor of two. For example, the calibrated non-dimensional in-plane edge stiffness in Section IV was found to be 0.5, which means the correct value is 1. Specific affected figures are Fig. 5, 6, and 7. References [6] Freydin M., Dowell E. H. and , “Nonlinear Theoretical Aeroelastic Model of a Plate: Free to Fixed In-Plane Boundaries,” AIAA Journal, Vol. 59, No. 2, 2021. https://doi.org/10.2514/1.J059551 Google Scholar Previous article FiguresReferencesRelatedDetailsRelated articlesNatural Frequencies of a Heated Plate: Theory and Experiment2 Sep 2020AIAA Journal What's Popular Volume 59, Number 6June 2021 Crossmark TopicsContinuum MechanicsMaterials and Structural MechanicsSolid MechanicsStructural Mechanics KeywordsPlate TheoryPDF Received16 April 2021Accepted16 April 2021Published online7 May 2021}, number={6}, journal={AIAA JOURNAL}, author={Freydin, Maxim and Levin, Dani and Dowell, Earl H. and Varigonda, Santosh Vaibhav and Narayanaswamy, Venkateswaran}, year={2021}, month={May}, pages={AU2–AU2} }
 @article{freydin_levin_dowell_varigonda_narayanaswamy_2020, title={Natural Frequencies of a Heated Plate: Theory and Experiment}, volume={58}, ISSN={["1533-385X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85095131109&partnerID=MN8TOARS}, DOI={10.2514/1.J059660}, abstractNote={No AccessTechnical NotesNatural Frequencies of a Heated Plate: Theory and ExperimentCorrections for this articleCorrection: Natural Frequencies of a Heated Plate: Theory and ExperimentMaxim Freydin, Dani Levin, Earl H. Dowell, Santosh Vaibhav Varigonda and Venkateswaran NarayanaswamyMaxim FreydinDuke University, Durham, North Carolina 27708*Graduate Research Assistant, Department of Mechanical Engineering and Materials Science. Student Member AIAA.Search for more papers by this author, Dani LevinDuke University, Durham, North Carolina 27708*Graduate Research Assistant, Department of Mechanical Engineering and Materials Science. Student Member AIAA.Search for more papers by this author, Earl H. DowellDuke University, Durham, North Carolina 27708†William Holland Hall Professor, Department of Mechanical Engineering and Materials Science. Honorary Fellow AIAA.Search for more papers by this author, Santosh Vaibhav VarigondaNorth Carolina State University, Raleigh, North Carolina 27695‡Graduate Research Assistant, Department of Mechanical and Aerospace Engineering.Search for more papers by this author and Venkateswaran NarayanaswamyNorth Carolina State University, Raleigh, North Carolina 27695§Associate Professor, Department of Mechanical and Aerospace Engineering. Senior Member AIAA.Search for more papers by this authorPublished Online:2 Sep 2020https://doi.org/10.2514/1.J059660SectionsRead Now ToolsAdd to favoritesDownload citationTrack citations ShareShare onFacebookTwitterLinked InRedditEmail About References [1] Whalen T. J., Schöneich A. G., Laurence S. J., Sullivan B. T., Bodony D. J., Freydin M., Dowell E. H. and Buck G. M., “Hypersonic Fluid–Structure Interactions in Compression Corner Shock-Wave/Boundary-Layer Interaction,” AIAA Journal, Vol. XX, No. XX, July 2020, pp. XX. https://doi.org/10.2514/1.J059152 Google Scholar[2] Freydin M., Dowell E. H., Whalen T. J. and Laurence S. J., “A Theoretical Computational Model of a Plate in Hypersonic Flow,” Journal of Fluids and Structures, Vol. 93, Feb. 2020, Paper 102858. https://doi.org/10.1016/j.jfluidstructs.2019.102858 CrossrefGoogle Scholar[3] Spottswood S. M., Beberniss T. J., Eason T. G., Perez R. A., Donbar J. M., Ehrhardt D. A. and Riley Z. B., “Exploring the Response of a Thin, Flexible Panel to Shock-Turbulent Boundary-Layer Interactions,” Journal of Sound and Vibration, Vol. 443, March 2019, pp. 74–89. https://doi.org/10.1016/j.jsv.2018.11.035 CrossrefGoogle Scholar[4] Santos Silva A. C., Sebastian C. M., Lambros J. and Patterson E. A., “High Temperature Modal Analysis of a Non-Uniformly Heated Rectangular Plate: Experiments and Simulations,” Journal of Sound and Vibration, Vol. 443, March 2019, pp. 397–410. https://doi.org/10.1016/j.jsv.2018.11.041 CrossrefGoogle Scholar[5] Ehrhardt D. A. and Virgin L. N., “Experiments on the Thermal Post-Buckling of Panels, Including Localized Heating,” Journal of Sound and Vibration, Vol. 439, Jan. 2019, pp. 300–309. https://doi.org/10.1016/j.jsv.2018.08.043 CrossrefGoogle Scholar[6] Freydin M. and Dowell E. H., “Nonlinear Theoretical Aeroelastic Model of a Plate: Free to Fixed In-Plane Boundaries,” AIAA Journal (under review). Google Scholar[7] Freydin M. and Dowell E. H., “Nonlinear Theoretical/Computational Model of a Plate in Hypersonic Flow with Arbitrary In-Plane Stiffness at the Boundaries,” Second International Symposium on Flutter and Its Application, May 2020, pp. 196–205, https://www.ladhyx.polytechnique.fr/isfa2020/proceedings.html. Google Scholar[8] Dowell E. H. and Voss H. M., “The Effect of a Cavity on Panel Vibration,” AIAA Journal, Vol. 1, No. 2, 1963, pp. 476–477. https://doi.org/10.2514/3.1568 LinkGoogle Scholar[9] Dowell E. H., Aeroelasticity of Plates and Shells, Springer, Berlin, 1974, pp. 48–49. Google Scholar Previous article Next article FiguresReferencesRelatedDetailsCited byHypersonic Fluid–Structure Interaction on a Cone–Slice–Ramp GeometryAnshuman Pandey, Katya M. Casper, Steven J. Beresh, Rajkumar Bhakta and Russell Spillers12 February 2023 | AIAA Journal, Vol. 0, No. 0Response of a plate with piezoelectric elements to turbulent pressure fluctuation in supersonic flowJournal of Fluids and Structures, Vol. 114Demonstration of Internal-Digital Image Correlation (Internal-DIC) for Fluid-Structure Interaction Measurements in a Hypersonic Wind TunnelAnshuman Pandey, Bryan E. Schmidt and Katya M. Casper20 June 2022An Experimental and Computational Correlation Study for Fluid-Thermal-Structural Interaction of a Control Surface in Hypersonic FlowAravinth Sadagopan, Daning Huang, Adam Jirasek, Jürgen Seidel, Anshuman Pandey and Katya M. Casper29 December 2021Fluid/Structural/Thermal/Dynamics Interaction (FSTDI) in Hypersonic Flow16 October 2021Supersonic Aerothermoelastic Experiments of Aerospace StructuresS. Michael Spottswood, Benjamin P. Smarslok, Ricardo A. Perez, Timothy J. Beberniss, Benjamin J. Hagen, Zachary B. Riley, Kirk R. Brouwer and David A. Ehrhardt6 October 2021 | AIAA Journal, Vol. 59, No. 12Methodology to image the panel surface pressure power spectra in weakly coupled fluid/structure interactions28 October 2021 | Experiments in Fluids, Vol. 62, No. 11Impact of Panel Vibrations on the Dynamic Field Properties in Supersonic flowSantosh Vaibhav Varigonda, Chase Jenquin and Venkateswaran Narayanaswamy28 July 2021Fully Coupled Nonlinear Aerothermoelastic Computational Model of a Plate in Hypersonic FlowMaxim Freydin and Earl H. Dowell14 June 2021 | AIAA Journal, Vol. 59, No. 7Hypersonic Fluid-Structure Interaction on the Control Surface of a Slender ConeAnshuman Pandey and Katya M. Casper4 January 2021Fluid-Thermal-Structural Interactions in Ramp-Induced Shock-Wave Boundary-Layer Interactions at Mach 6Antonio Giovanni Schöneich, Thomas J. Whalen, Stuart J. Laurence, Bryson T. Sullivan, Daniel J. Bodony, Maxim Freydin, Earl H. Dowell, Larson J. Stacey and Gregory M. Buck4 January 2021Related articlesCorrection: Natural Frequencies of a Heated Plate: Theory and Experiment7 May 2021AIAA Journal What's Popular Volume 58, Number 11November 2020Supplemental Materials CrossmarkInformationCopyright © 2020 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. All requests for copying and permission to reprint should be submitted to CCC at www.copyright.com; employ the eISSN 1533-385X to initiate your request. See also AIAA Rights and Permissions www.aiaa.org/randp. TopicsAerodynamicsAeronautical EngineeringAeronauticsAerothermodynamicsComputational Fluid DynamicsFinite Element MethodFlow RegimesFluid DynamicsFluid MechanicsFluid Structure InteractionNumerical AnalysisThermodynamicsThermophysics and Heat TransferWind Tunnels KeywordsStatic PressurePlate TheoryHypersonic Wind TunnelsFinite Element ModelingThermal StressesAerodynamic ForceMaterial PropertiesData AcquisitionFSIStructural ModelingAcknowledgmentsThis work was supported in part by a U.S. Air Force Office of Scientific Research grant with Jaimie Tiley as the Program Director. The authors would like to thank Jaimie Tiley and Ivett Leyva for their encouragement and guidance.PDF Received3 April 2020Accepted4 August 2020Published online2 September 2020}, number={11}, journal={AIAA JOURNAL}, author={Freydin, Maxim and Levin, Dani and Dowell, Earl H. and Varigonda, Santosh Vaibhav and Narayanaswamy, Venkateswaran}, year={2020}, month={Nov}, pages={4969–4973} }