Numerical modeling of turbulent compound channel flow using the lattice Boltzmann method

The flow of water in a straight Compound channel with prismatic cross section is investigated with a relatively new tool, the lattice Boltzmann method. The large eddy Simulation model is added in the lattice Boltzmann model for nonlinear shallow water equations (LABSWE (TM)) so that the turbulence, caused by lateral exchange of momentum in the shear layer between the main channel and floodplain, call be taken into account and modeled efficiently. To validate the numerical model, a symmetrical compound channel with trapezoidal main channel and flat floodplain is tested. Similar to most natural watercourses, the floodplain has higher toughness values than the main channel. Different relative depths, D-r (the ratio of the depth of flow on the floodplain to that in the main channel), are considered. The Reynolds number is set at 30000 in the main channel. The lateral distributions of the longitudinal velocity, the boundary shear stress, the Reynolds stress and the apparent shear stress across the channel are obtained after the large eddy simulation is performed. The results of numerical simulations are compared with the available experiment data, which show that the LABSWE (TM) is capable of modeling the features of flow turbulence in compound channels and is sufficiently accurate for practical applications in engineering. Copyright (C) 2008 John Wiley & Sons, Ltd.