NUMERICAL INVESTIGATION OF TURBULENT SHALLOW RECIRCULATING-FLOWS BY AQUASI-3-DIMENSIONAL K-EPSILON-MODEL

A quasi-three-dimensional multilayer k-epsilon model has been develope d to simulate turbulent recirculating flows behind a sudden expansion in shallow waters. The model accounts for the vertical variation in th e flow quantities and eliminates the problem of closure for the effect ive stresses resulting From the depth integration of the non-linear co nvective accelerations found in the widely used depth-integrated model s. The governing equations are split into three parts in the finite di fference solution: advection, dispersion and propagation. The advectio n part is solved using the four-node minimax-characteristics method. T he dispersion and propagation parts are treated by the central differe nce method, the former being solved explicitly and the latter implicit ly using the Gauss-Seidel iteration method. The relative effect of bed -generated turbulence and transverse shear-generated turbulence on the recirculating flow has been studied in detail. In comparison with the results computed by the depth-integrated k-epsilon model, the results computed by the present model are found to be closer to the reported data.