Wall-Modeled Large-Eddy Simulations of Mach 14 Turbulent Boundary Layer - Aero-Optical Distortions

Abstract

A wall-modeled large-eddy simulation of a Mach 14 boundary layer flow over a flat plate was carried out for the conditions of the Arnold Engineering Development Complex Hypervelocity Tunnel 9. Adequate agreement of the mean velocity and temperature, as well as Reynolds stress profiles with a reference direct numerical simulation is obtained at much reduced grid resolution. The normalized root-mean-square optical path difference obtained from the present wall-modeled large-eddy simulations and reference direct numerical simulation are in good agreement with each other but below a prediction obtained from a semi-analytical relationship by Notre Dame University. This motivates an evaluation of the underlying assumptions of the Notre Dame model at high Mach number. For the analysis, recourse is taken to previously published wall-modeled large-eddy simulations of a Mach eight turbulent boundary layer. The analysis of the underlying assumptions focuses on the root-mean-square fluctuations of the thermodynamic quantities, on the strong Reynolds analogy, two-point correlations, and the linking equation. It is found that with increasing Mach number, the pressure fluctuations increase and the strong Reynolds analogy over-predicts the temperature fluctuations. In addition, the peak of the correlation length shifts towards the boundary layer edge.