Compressibility Effects on Turbulent Separated Flow in a Streamwise-Periodic Hill Channel—Part 1

Abstract

We present large-eddy simulation (LES) results of the streamwise-periodic hill channel configuration, which is a standard test case for massively separated flows. The Reynolds number (computed with the hill height, the bulk mass flux through the cross-section above the hill crest and the dynamic viscosity at the wall) is chosen as 2,800, in accordance with recent DNS data from Peller & Manhart [4] for incompressible flow. The Mach number was varied between Ma= 0.2 and Ma = 2.5. The numerical simulation code NSMB discretises the compressible Navier-Stokes equations with the finite-volume method on a deliberately-chosen coarse structured mesh. The subgrid-scales are accounted for by the well-proven approximate deconvolution model (ADM).

This investigation is an extension of our previous work on this configuration, which focused on the validation of our simulation approach at nearly incompressible flow conditions. In this first part of a two-part contribution [8], the scope lies primarily on the effect of compressibility, especially on the separation characteristics and the flow conditions at the walls. To this end, we introduce a new measure that quantifies reverse flow at the walls and study the distributions of the friction and pressure coefficients. Unlike other investigations of this flow case, we also include the upper wall in this study. Furthermore, we describe the dependence of the turbulence and separation characteristics on the Mach number.