Large-eddy simulation of separated flow in a channel with streamwise-periodic constrictions

Large-eddy simulations using the approximate-deconvolution subgrid-scale model of compressible flow in a channel with streamwise-periodic constrictions are performed at two Reynolds numbers of 2800 and 10,595. The goal of the study is the evaluation of this subgrid-scale model for massively separated flows. The Mach number was chosen as 0.2 to facilitate comparison with incompressible flow data. A relatively coarse structured grid and a finite-volume discretization employing a skew-symmetric fourth-order central scheme are used with a four-stage Runge-Kutta method for time integration. The results are compared to data from the literature obtained with incompressible direct numerical simulations, as well as highly resolved large-eddy simulations. Despite the chosen coarse resolution, good agreement of the statistical quantities and important flow features, such as separation and reattachment locations, is achieved. In contrast to previous works we also consider the flow properties at the straight upper wall. We introduce a new measure quantifying the time fraction of reverse flow along the wall. Furthermore, we analyze the energy density spectra of the velocity fluctuations and study the turbulence structure with Lumley's flatness parameter and realizability map. We also illustrate the vortex systems associated with the shedding and other instantaneous flow structures.