Numerical Investigation of Transitional Shock-Wave/Boundary-Layer Interaction in Supersonic Regime

Direct numerical simulations of shock-wave/boundary-layer interactions are performed at Mach number M-infinity=1.7 to investigate the influence of the state of the incoming boundary layer on the interaction properties. Four shock-wave/boundary-layer interaction cases are considered, corresponding to transitional and turbulent interactions for two different shock strengths, corresponding to flow-deflection angles phi=3 deg and phi=6 deg. It is found that significant separation is not evident in the mean flow of any interaction; the boundary layer remains attached at phi=3 deg and close to incipient separation at phi=6 deg, independent of the state of the incoming boundary layer. The extent of the interaction is larger for the transitional flow cases, characterized by a wider spreading of the wall pressure rise and a slower boundary-layer recovery. The scaling analysis for the interaction length scale L developed by Souverein etal. ("A Scaling Analysis for Turbulent Shock-Wave/Boundary-Layer Interactions," Journal of Fluid Mechanics, Vol.714, January 2013, pp.505-535) for turbulent interactions is found to be equally applicable for the transitional interactions. The wall-pressure spectra show that the dominant frequency range is that associated with the most energetic structures of the incoming boundary layer, and no evidence of low-frequency shock unsteadiness is noticed.