Response of hypersonic boundary-layer disturbances to compression and expansion corners

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dc.contributor.advisorLaurence, Stuarten_US
dc.contributor.authorButler, Cameron Scotten_US
dc.contributor.departmentAerospace Engineeringen_US
dc.contributor.publisherDigital Repository at the University of Marylanden_US
dc.contributor.publisherUniversity of Maryland (College Park, Md.)en_US
dc.date.accessioned2021-07-13T05:32:20Z
dc.date.available2021-07-13T05:32:20Z
dc.date.issued2021en_US
dc.description.abstractAn experimental campaign was conducted at the University of Maryland - College Park to examine the impact of abrupt changes in surface geometry on hypersonic boundary-layer instability waves. A model consisting of a 5-degree conical forebody was selected to encourage the dominance of second-mode wavepackets upstream of the interaction region. Interchangeable afterbody attachments corresponding to flow deflections of -5-degree to +15-degree in 5-degree increments were considered. The adverse pressure gradient imposed by the +10-degree and +15-degree configurations caused the boundary layer to separate upstream, creating a region of recirculating flow. High-speed schlieren (440-822 kHz) was employed as the primary means of flow interrogation, with supplemental surface measurements provided by PCB132B38 pressure transducers. A lens calibration was applied to the images to provide quantitative fluctuations in density gradient. The high frame rate made possible the use of spectral analysis techniques throughout the entire field of view. This analysis reveals complex growth and decay trends for incoming second-mode disturbances. Additional, low-frequency content is generated by the deflected configurations. This is most pronounced for the separated cases where distinct, shear-generated disturbances are observed. Spectral proper orthogonal decomposition (SPOD) is demonstrated as a powerful tool for resolving the flow structures tied to amplifying frequencies. Nonlinear interactions are probed through bispectral analysis. Resonance of low-frequency structures is found to play a large role in nonlinear energy transfer downstream of the compression corners, particularly for the separated cases. Concave streamline curvature appears to result in concentrated regions of increased nonlinearity. These nonlinear interactions are shown to be spatially correlated with coherent flow structures resolved through SPOD. Finally, a limited computational study is carried out to demonstrate the ability of linear stability theory and the parabolized stability equations to reproduce experimental results obtained for the +10-degree extension. The development of the second-mode and shear-generated disturbances resolved by the computational analysis shows excellent agreement with the experimental results.en_US
dc.identifierhttps://doi.org/10.13016/aemg-dmg3
dc.identifier.urihttp://hdl.handle.net/1903/27352
dc.language.isoenen_US
dc.subject.pqcontrolledAerospace engineeringen_US
dc.subject.pquncontrolledBoundary layeren_US
dc.subject.pquncontrolledCompressionen_US
dc.subject.pquncontrolledExpansionen_US
dc.subject.pquncontrolledHypersonicen_US
dc.subject.pquncontrolledSeparationen_US
dc.subject.pquncontrolledTransitionen_US
dc.titleResponse of hypersonic boundary-layer disturbances to compression and expansion cornersen_US
dc.typeDissertationen_US

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