DIRECT AND LARGE-EDDY SIMULATION AND ANALYSIS OF SHOCK-SEPARATED FLOWS

Abstract

The in-house CRoCCo code is used to generate a database of high-fidelity direct numerical simulation (DNS) and large eddy simulation (LES) data of shock wave and turbulent boundary layer interactions (STBLI) at supersonic to hypersonic conditions. The DNS data is employed in the validation of the LES method and the assessment of the sub-grid-scale (SGS) models in application to the STBLI flow problem. It is determined that, under hypersonic conditions, a scale similar model term in both the shear stress and heat transfers SGS terms is necessary to produce the correct STBLI separation flow. The use of the dynamic eddy viscosity term alone produced as much as 30% error in separation length. The high grid-resolving efficiency (equivalently the practicality over the DNS) of the CRoCCo code LES method for the simulation of STBLI flows is also demonstrated with a typical reduction of 95% grid size and 67% in number of time steps as compared to the DNS, a feature that makes spectral convergence of the STBLI low-frequency cycle feasible.

The thorough documentation of DNS-validated, high-fidelity LES solutions of hypersonic STBLI flows is a unique contribution of this work. Thanks to the detail in the turbulence data afforded by the LES, an extensive and novel characterization of the separation shear layer in the STBLI flows is possible and the results are related to compressible mixing layer theory. In addition, visualizations of the numerical data show the form of the inviscid instability in hypersonic shock-separated flows. These visualizations combined with the extended CRoCCo Lab numerical database provide significant insight into the nature of the separation length scaling in STBLI at hypersonic Mach numbers.