ENTROPY CONSIDERATIONS APPLIED TO SHOCK UNSTEADINESS IN HYPERSONIC INLETS.

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dc.contributor.advisorLewis, Mark Jen_US
dc.contributor.authorBussey, Gillian Mary Hardingen_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.accessioned2013-02-06T06:38:02Z
dc.date.available2013-02-06T06:38:02Z
dc.date.issued2012en_US
dc.description.abstractThe stability of curved or rectangular shocks in hypersonic inlets in reponse to flow perturbations can be determined analytically from the principle of minimum entropy. Unsteady shock wave motion can have a significant effect on the flow in a hypersonic inlet or combustor. According to the principle of minimum entropy, a stable thermodynamic state is one with the lowest entropy gain. A model based on piston theory and its limits has been developed for applying the principle of minimum entropy to quasi-steady flow. Relations are derived for analyzing the time-averaged entropy gain flux across a shock for quasi-steady perturbations in atmospheric conditions and angle as a perturbation in entropy gain flux from the steady state. Initial results from sweeping a wedge at Mach 10 through several degrees in AEDC's Tunnel 9 indicates the bow shock becomes unsteady near the predicted normal Mach number. Several curved shocks of varying curvature are compared to a straight shock with the same mean normal Mach number, pressure ratio, or temperature ratio. The present work provides analysis and guidelines for designing an inlet robust to off- design flight or perturbations in flow conditions an inlet is likely to face. It also suggests that inlets with curved shocks are less robust to off-design flight than those with straight shocks such as rectangular inlets. Relations for evaluating entropy perturbations for highly unsteady flow across a shock and limits on their use were also developed. The normal Mach number at which a shock could be stable to high frequency upstream perturbations increases as the speed of the shock motion increases and slightly decreases as the perturbation size increases. The present work advances the principle of minimum entropy theory by providing additional validity for using the theory for time-varying flows and applying it to shocks, specifically those in inlets. While this analytic tool is applied in the present work for evaluating the stability of shocks in hypersonic inlets, it can be used for an arbitrary application with a shock.en_US
dc.identifier.urihttp://hdl.handle.net/1903/13503
dc.subject.pqcontrolledAerospace engineeringen_US
dc.subject.pqcontrolledPhysicsen_US
dc.subject.pquncontrolledEntropyen_US
dc.subject.pquncontrolledHypersonic inletsen_US
dc.subject.pquncontrolledHypersonicsen_US
dc.subject.pquncontrolledScramjeten_US
dc.subject.pquncontrolledShock wavesen_US
dc.subject.pquncontrolledThermodynamicsen_US
dc.titleENTROPY CONSIDERATIONS APPLIED TO SHOCK UNSTEADINESS IN HYPERSONIC INLETS.en_US
dc.typeDissertationen_US

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