Simulations of a Mach 3 Compression-Ramp Interaction using LES/RANS Models

Abstract

Two large-eddy simulation / Reynolds-averaged Navier-Stokes (LES/RANS) models are applied to a shock / boundary interaction generated by a 20-degree compression corner. The models are designed to transition from unsteady RANS to LES as the boundary layer shifts from its logarithmic behavior to its wake-like response, but differ in that one model requires a pre-selection of a model constant for each problem, while the other computes this constant as a function of local and ensemble-averaged turbulence properties. Predictions are compared with mean-flow and second-moment experimental data obtained at Princeton University. In general, calculated mean-flow velocity, surface pressure, and surface skin friction distributions agree well with experiment, with the most noticeable discrepancy being a slight over-prediction of the level of upstream influence induced by the shock wave. Comparisons with mass-flux fluctuation intensity, Reynolds axial stress, and Reynolds shear stress profiles are also presented. These show good agreement with experimental trends relating to Reynolds-stress amplification and anisotropy modulation, particularly when assumptions used in hot-wire anemometry are employed in the computation of the Reynoldsstress profiles. The calculations also predict the existence of a low-frequency motion of the separation shock that is probably associated with the motion of the backflow region. Higherfrequency modulations of the shock front as induced by the passage of coherent, streak-like structures through the shock also appear to contribute to the measurable intermittency effects.