Large Eddy Simulation of the Flow Over non-confined Backward Facing Step Using High Order Compact Finite Difference Schemes

In the present study, large eddy simulation of unsteady, three-dimensional and turbulent flow over non-confined backward facing step (BFS) is numerically conducted. Due to the capability of the compact differential scheme in high-order solution of the compressible flow, this method is used to solve the filtered Navier-Stokes equations in the generalized curvilinear coordinate using a multi-block structured grid. To study the influence of the sub-grid scale (SGS) stress model, the Smagorinsky model, the MKEV model, the dynamic Smagorinsky model (DSM), and the WALE model are considered. The numerical results include the general characteristics of the flow over BFS such as the reattachment length, friction and pressure coefficients, the mean velocity and the Reynolds stresses. Moreover, the present LES results are compared with the available experimental data and DNS, LES and RANS results and a very good agreement is achieved. Moreover, the obtained results using the DSM and WALE models give a better agreement with the DNS and experimental data than those by Smagorinsky and MKEV models.