An Experimental Investigation of Hypersonic Boundary-Layer Transition on Sharp and Blunt Slender Cones

dc.contributor.advisorLaurence, Stuart Jen_US
dc.contributor.authorKennedy, Richard Edwarden_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.accessioned2020-02-01T06:44:46Z
dc.date.available2020-02-01T06:44:46Z
dc.date.issued2019en_US
dc.description.abstractUnderstanding the instabilities leading to the laminar-to-turbulent transition of a hypersonic boundary layer is a key challenge remaining for the design of efficient hypersonic vehicles. In the present study, experiments are performed in three different facilities at freestream Mach numbers between 6 and 14 to characterize instability mechanisms leading to transition on a 7-degree half-angle slender cone. Second-mode instability waves are visualized using a high-speed schlieren setup with the camera frame rate and spatial resolution optimized to allow individual disturbances to be tracked. In order to facilitate quantitative time-resolved measurements, a method of calibrating the schlieren system and novel image-processing algorithms have been developed. Good agreement is observed between the schlieren measurements, surface pressure measurements, and parabolized stability equation computations of the second-mode most-amplified frequencies and N factors. The high-frequency-resolution schlieren signals enable a bispectral analysis that reveals phase locking of higher harmonic content leading to nonlinear wave development. Individual disturbances are characterized using the schlieren wall-normal information not available from surface measurements. Experiments are also performed to investigate the effect of nose-tip bluntness. For moderate to large bluntness nose tips, second-mode instability waves are no longer visible, and elongated structures associated with nonmodal growth appear in the visualizations. The nonmodal features exhibit strong content between the boundary-layer and entropy-layer edges and are steeply inclined downstream. Simultaneously acquired surface pressure measurements reveal high-frequency pressure oscillations typical of second-mode instability waves associated with the trailing edge of the nonmodal features.en_US
dc.identifierhttps://doi.org/10.13016/hs94-qi6h
dc.identifier.urihttp://hdl.handle.net/1903/25483
dc.language.isoenen_US
dc.subject.pqcontrolledAerospace engineeringen_US
dc.subject.pqcontrolledFluid mechanicsen_US
dc.subject.pquncontrolledAerodynamicsen_US
dc.subject.pquncontrolledHypersonicsen_US
dc.subject.pquncontrolledStabilityen_US
dc.subject.pquncontrolledTransitionen_US
dc.titleAn Experimental Investigation of Hypersonic Boundary-Layer Transition on Sharp and Blunt Slender Conesen_US
dc.typeDissertationen_US

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