Direct numerical simulation of a backward-facing step at Re_tau=395 and an expansion ratio 2

A direct numerical simulation (DNS) of the turbulent flow over a backward-facing step (BFS) at Re_tau=395 (based on the channel half height and the skin friction velocity at the inflow) with an expansion ratio equal to 2 has been carried out. The dimensions of the computational domain are 38h × 2h × 2pih in the stream-wise, cross-stream and span-wise direction, respectively, where h is the step height. A fully developed turbulent channel flow at Re_tau=395 is placed at the inflow whereas convective boundary condition are used at the outflow. Periodic boundary conditions are imposed in the span-wise direction. Finally, non-slip boundary conditions are imposed at the walls. We have used a 1510 x 302 x 360  (~164M grid points) staggered mesh to cover the computational domain. The grid is concentrated around the expansion and re-circulation regions by means of piece-wise tanh-functions. A fourth-order energy-conserving spatial discretization has been used. You can find more details in: ílchez, ,