Computation of flow over backward-facing step without and with free surface

A finite difference method for the solution of the two-dimensional incompressible Reynolds-averaged Navier-Stokes equations, is used to simulate the flow over a backward-facing step without and with a free surface. For the turbulent flow, a two-layer turbulence model is employed for the turbulence closure. In case of the backward-facing step flow without free surface, the present results compare favorably with the measurements for the reattachment points, the pressure distribution and the velocity profiles. For those with a free surface, because experimental data is not available at present moment, only qualitative comparisons are made with some relevant results. It is shown that the computed flows exhibit many distinctive features of interest, including the recirculating zone, the surface wave, and their interactions.