CALCULATION OF FLOW OVER BACKWORD-FACING STEP IN OPEN CHANNEL USING LOW-REYNOLDS NUMBER TURBULENCE MODEL

Low-Reynolds number turbulence models have been incorporated in the computational method for two-dimensional but complex turbulent flows with a free surface and flow separation so that the boundary complexity and the mean position of the free surface are directly represented. The models used are one of the low-Reynolds number k-ε methods that has been proved accurate in simple geometry and the k-ω model that is known to be versatile. Calculations have been performed for flow over a backward-facing step in open channel and the results are compared with experiments and calculations with conventional high-Reynolds number model. Overall results using the low-Reynolds number models do not drastically improve over the high-Reynolds number version using wall-function assumptions, but they do show marked improvements in the recirculating region near the wall.