Shock-wave/turbulent boundary layer interaction over curved compression ramp*

In this study, the shock-wave/turbulent boundary layer interaction over concave surfaces with two different radii of curvature is compared to a compression ramp for a free stream Mach number M_∞ = 2.9 and Reynolds number Re_θ = 2400 using direct numerical simulation. Both the compression ramp (R24) and the curved compression ramps have a total turning angle of 24°, with the radii of curvature of the curved ramps being 7 (C7) and 14 (C14) times the thickness of the incoming turbulent boundary layer. The rounding of the corner mitigates the relaxation effect of the adverse pressure gradient, thereby influencing the formation of the separation bubble. Both R24 and C7 exhibit transitory detachment, with R24 displaying a rear-strong separation bubble and C7 showing a frontal-strong separation bubble. In contrast, C14 experiences incipient detachment, which does not lead to the formation of a mean separation bubble. The turbulent kinetic energy (TKE) is amplified across the ramps. While R24 shows both first and second TKE amplification points, C7 lacks the second amplification. Overall, TKE amplification is lower over C14, but the second amplification is distinctly prominent. The power spectrum density of wall pressure fluctuations reveals low-frequency instability in both R24 and C7 cases, while mid-frequency instability is suppressed due to the corner rounding on C7. Notably, the C14 case does not exhibit evident low-frequency instability.