Shock-Wave/Boundary-Layer Interactions at Compression Ramps Studied by High-Speed Schlieren

The shock-wave/boundary-layer interactions (SWBLIs) at compression ramps (ramp angle alpha=20-30 deg) are studied at Ma=2.0 and under two Reynolds numbers (Re1=18,600 and Re2=35,600, with the Reynolds number Re based on boundary-layer thickness). High-speed schlieren operating at 20 kHz are used as the flow diagnostics. The flow structures in the compression ramp SWBLIs (including the shock wave, interaction region, and induced turbulent region over the ramp surface) are discussed. Their variations under increasing ramp angles and Reynolds numbers are further examined. The low-frequency shock-wave oscillations are also studied through tracking the shock-wave motion. A larger ramp angle increases the spectral intensity of the shock wave's low-frequency unsteadiness, whereas increasing the Reynolds number results in a lower peak frequency for the separation and reattachment shock waves.