MODIFICATION OF k-ε TURBULENCE CLOSURE AND ITS APPLICATION TO MEANDERING COMPOUND CHANNEL FLOW

The two-equation k-ε turbulence model is modified by making the eddy viscosity in horizontal directions different from that in the vertical. The correction is referred to an approximate expression of shear stress in the turbulence algebraic stress/flux model. With the modified k-ε turbulence closure, a 3D flow model is developed by solving the Reynolds equations with hydrostatic pressure approximation. Furthermore, bed variation is calculated on the basis of 3D numerical solution of water flow. The computed results for the flow and bed deformation in a sine-generated meandering compound channel are better than those with standard k-ε closure and agree with the measurements. The calculations show that the center of dominant secondary currents is around the level of flood plain. The transverse flow near the surface is governed by the water surface slope instead of the centrifugal force. The secondary currents show an interesting variation with the water depth ratio between flood plain and main channel.