Structure and Unsteadiness of Swept-Ramp Shock Wave/Turbulent Boundary Layer Interactions

In this study we investigate the flow structure and large-scale unsteadiness of a 3D shock wave/turbulent boundary layer interaction generated by a swept compression ramp in a Mach 2 flow. The unsteady dynamics of the flow are investigated using 50 kHz particle image velocimetry (PIV) in side-view and plan-view planes. The 50 kHz PIV velocity data are bandpass-filtered to investigate potential mechanisms that drive the large-scale unsteadiness. Our analysis shows that strong correlation exists between velocity fluctuations in the upstream boundary layer and motion of the separation-line surrogate for frequencies lower than 10 kHz (0.25 U∞/δ99). This frequency band correlates well with the characteristic frequency range of boundary layer superstructures. Separated flow motions in the high-frequency band (10–50 kHz) do not seem to be strongly correlated to the upstream flow, instead significant correlation is observed with structures within the separation region that move primarily in the cross-stream direction.