Wall-Modeled Large-Eddy Simulation of Supersonic Flow over Backward-Facing Step for Aero-Optical Distortion Analysis

Abstract

This paper reports on compressible wall-modeled large-eddy simulations of a Mach two turbulent boundary layer flow over a cavity. The cavity is defined by a backward-facing step and a compression ramp. The freestream and wall boundary conditions as well as the momentum thickness Reynolds number for the simulations are identical to those of experiments in the Tri-Sonic Wind Tunnel at Notre Dame University. The objective of the research is to understand and predict the aero-optical distortion caused by high-speed turbulent boundary layer flows over optical windows with film cooling. For the present simulation, the cooling film was not considered. Profiles of the root-mean-square velocity fluctuations upstream of the step and velocity profiles downstream of the step compare favorably with available data in the literature. The normalized root-mean-square optical path distortion for the approach boundary layer is in good agreement with a semi-analytical model by Notre Dame University. A preliminary analysis of the optical path distortion downstream of the step indicates a large streamwise variation for the recirculation region and moderate fluctuations downstream of reattachment.