Shock Perturbations in Hypersonic Attached Shock-Wave/Turbulent-Boundary-Layer Interactions

Abstract

An experimental campaign was conducted in the University of Maryland, College Park’s High-Temperature Ludwieg Tube to examine turbulent shock-wave/boundary-layer interactions (SWBLI) on a conical compression-corner configuration at Mach 6.25. The SWBLI behavior was analyzed for multiple test conditions on five cone-flare configurations–a straight cone and four compression angles of 5◦, 10◦, 15◦, and 20◦–which all result in attached interactions at the junction. Unsteady oscillatory behavior along the shock was examined through high-speed schlieren imaging. Edge-detection techniques and correlation speed analysis were used to characterize the propagation speeds of turbulent structures and resulting flare-shock disturbances, frequency content along the shock, and interaction unsteadiness. Fluctuations observed along the shock were shown to remain relatively constant in amplitude as they propagate; a spatial frequency analysis showed that these were not favorable to any specific wavenumbers. As the compression angle increased, root mean square perturbation amplitudes decreased and the spatial wavenumber spectra dropped off more rapidly. The propagation speed of the shock disturbances was found to decrease as the compression angle of the flare increased, aligning more closely with the mean propagation speed of the flare boundary layer than that of the cone boundary layer. This suggests that the region downstream of the corner has influence on the shock behavior and that the shock could be receptive to disturbances in the region downstream of the corner. Additionally, the computed perturbation amplitudes were used along with the propagation speeds of disturbances to characterize how large upstream boundary-layer structures manifested in the compression shock region. Statistical analyses revealed modest increases in the mean, standard deviation, and root mean square shock perturbation amplitudes when large disturbances were present in the upstream boundary layer. The relative increase grew slightly with increasing compression angle and diminished slightly with increasing Reynolds number. The modest trends suggest that other features within the interaction had a more dominant effect on exciting the shock perturbations.