Experimental study of swept impinging oblique shock boundary layer interaction

An experimental investigation has been conducted on swept impinging oblique shock/boundary layer interactions (SBLIs) at Mach 2.3. The incoming boundary layer is turbulent with (Re_θ = 5.5 × 10³). The swept impinging oblique shock is induced by a shock generator mounted in the freestream with x-y plane deflection angle θ = 12.5◦ and variable x-z plane sweep angles of 15.0◦, 22.5◦, 30.0◦, and 40.0◦. Oil flow visualization, particle image velocimetry (PIV), mean pressure measurements and fast-response pressure transducers are used to provide detailed characterization of the mean and unsteady features of the SBLIs. Large scale separation is observed in all cases with spanwise growth evident at high shock generator sweep angles. At the onset of separation in the quasi-infinite region, mean pressures are independent of span and scale cylindrically. However, mean pressures at reattachment display a mild dependency on the span, suggesting the global structure of the SBLIs is conical in nature. This agrees with supporting tomographic PIV measurements. Unsteady pressure measurements beneath the separation shock foot for the ψ = 30.0◦ SBLI shows clear low frequency unsteadiness across the span at nearly constant frequency. Spanwise travelling ripples are present at the shock foot with considerable coherence in the low frequency range. The spanwise convection speed of these ripples increases with span suggesting that the wavelength also increases. Minimal upstream influence is associated with the low frequency unsteadiness, suggesting a source mechanism within the SBLI.