Sweep effects on a canonical shock wave/boundary layer interaction

Abstract

In this study, we use wall-resolved large-eddy simulations to investigate how the presence of a sweep angle in the upstream flow affects a canonical situation involving shock/boundary layer interaction (SBLI). The chosen configuration is based on the experiments of Bo et al. (2012) where an incident shock impinges on a turbulent boundary layer developing at a freestream Mach number of M=2.7, with a Reynolds number based on the momentum thickness of Reθ=3200. The sweep angle is implemented by adding a spanwise velocity component (crossflow) at the inflow and enforcing periodicity conditions on the side boundaries. This corresponds to an idealized configuration of swept SBLI that is unable to reproduce the conical symmetry found in some real-life applications. Several sweep angles are investigated and compared to a reference unswept case. A viscosity is selected for each case in an effort to keep a constant Reθ across the whole range of sweep angles. The mean flow structure is analysed, showing a strongly skewed flow around the separation zone which increases in size compared to the unswept case. Pressure loads on the wall surface are also higher for swept cases; and the characteristic low-frequencies of the flow separation also slightly increase with significant energy density around a Strouhal number based on the separation length and freestream velocity of StLsep=0.15. Proper orthogonal decomposition (POD) is then applied to obtain more accurate informations on the unsteadiness around the interaction area. This analysis reveals in the swept cases the formation of streamwise-elongated structures related to this new frequency of StLsep=0.15 and moving along the spanwise direction at a convection velocity of about 80% of the transverse freestream velocity.