Density-Based Spectral Analysis of a Turbulent Compression Ramp Shock Boundary Layer Interaction at Mach 2.3

Abstract

Quantitative high-speed schlieren imaging and various spectral analysis techniques are employed to characterize low frequency unsteadiness observed in an unswept θ = 22° compression ramp-induced Shock Boundary Layer Interaction (SBLI). The incoming boundary layer is turbulent with Reθ = 5600 and the Mach number is 2.3. Results are supported by data from wall-mounted fast-response pressure transducers. Both techniques observe similar frequencies of the separation shock with dominant energy at Stδ0 ≈ 0.01 and StL ≈ 0.02. Detailed comparisons are performed with an analogous transitional Mach 4 compression ramp SBLI investigated in the same facility. Downstream features - such as the shear layer, reattachment shock, and transient events within the separation bubble - are highly coherent with and lead the characteristic separation shock motion by approximately −0.25π, while upstream features - such as the boundary layer - also lead but are less coherent, affirming the importance of downstream influences on turbulent SBLI within the given flow regimes. Major comparative findings between this turbulent Mach 2.3 SBLI study and the analogous transitional Mach 4 study include: 1) broadly identical coherence between major SBLI features (minus the turbulent boundary layer) and; 2) broadly identical phase relationships between major SBLI features (the shear layer, reattachment shock, and transient bubble events) despite the difference in boundary layer state and flow speed.