Sharp-Fin-Induced Hypersonic Shock-Wave/Boundary-Layer Interactions

Abstract

A series of experimental campaigns were conducted to study the hypersonic shockwave/boundary-layer interaction (SWBLI) generated by a sharp fin on a flat plate. A campaign focusing on the case of a transitional incoming boundary layer was investigated in the HyperTERP reflected-shock facility. This campaign demonstrated the viability of fast-responsetemperature-sensitive paint as a diagnostic technique for a facility of this scale and also showed the value of a plan-view schlieren made possible through flush-mounted windows. Results showed the presence of quasi-conical symmetry for this transitional SWBLI and a significant level of unsteadiness in the inception region and near the separation line. Schlieren results showed the ability to identify the line of upstream influence from a power spectral density analysis of the plan-view data. The new high-temperature Ludwieg tube (HTLT) facility at the University of Maryland, College Park was characterized for both Mach-6.25 and Mach-8 configurations. The Mach-6.25 Pitot rake survey showed test times of ~100ms with a core flow diameter >184mm. In the Mach-6.25 configuration, the facility is able to generate Reynolds numbers of up to 44x10^6 m^-1. The Mach-8 Pitot rake survey showed test times of 40-80ms with a core flow diameter of roughly 300mm with the ability to reach Reynolds numbers of 13x10^6 m^-1. These measurements were corroborated by schlieren imaging and Femtosecond Laser Electronic Excitation Tagging velocimetry. Neither the Pitot rake surveys nor the velocimetry measurements showed any evidence of the presence of a wake generated by the piston system through which the facility operates. Subsequently, an experimental campaign was conducted in the HTLT facility investigating the fin-induced SWBLI in the case of a turbulent incoming boundary layer. Heat-flux distributions show the progression through different flow regimes and the presence of quasi-conical symmetry. At higher interaction strengths, the appearance of a tertiary peak and secondary trough in the heat flux may be indicative of the onset of secondary separation and reattachment. A survey over the parameter space shows an influence of both Reynolds number and interaction strength on quantities such as maximum surface heating and the spatial distribution of the heat flux. High-speed plan-view schlieren imaging shows broadband elevated energy levels between the shock wave and the fin surface.