Effect of sweep on the mean and unsteady structures of impinging shock/boundary layer interactions

An experimental investigation has been conducted to assess the effect of sweep on impinging oblique Shock/Boundary Layer Interactions (SBLIs), specifically focused on the distribution of mean and fluctuating pressure signatures at the wall. Four shock generators are utilized with x-y plane deflection of θ = 12.5^◦, and x-z plane sweep angles of 15.0^◦, 22.5^◦, 30.0^◦, and 40.0^◦. The induced swept oblique shocks impinge upon the naturally turbulent Mach 2.3 boundary layer along the tunnel floor (Re_θ ≈ 5000). The resultant SBLIs all exhibit significant separation, with a structure that grows in the spanwise direction. Flow features are assessed using oil-flow visualization, static pressure tapings, and fast-response pressure transducers. The rise in mean pressure near separation scales locally with cylindrical similarity suggesting the three-dimensional separation along the span obeys Free Interaction Theory. Local reattachment behavior is only mildly dependent upon span, yet the overall shock structure is clearly conical. Low-frequency unsteadiness is observed beneath the separation shock foot in all cases, shifting towards higher frequencies as sweep is increased. Spanwise ripples in the separation shock attributed to the low-frequency wall-pressure signature travel along the shock span with velocities an order of magnitude below that of the freestream flow. Results offer a vital insight into characterizing swept SBLI behavior in a fundamental configuration that has been largely overlooked in literature.