Numerical modelling of flow field in compound channels with non-prismatic floodplains

Abstract

In this paper an attempt has been made to study flow field in compound channels with non-prismatic floodplains. A three dimensional computational fluid dynamic (CFD) model is used to calculate the velocity distribution, secondary flow circulation and boundary shear stress in non-prismatic compound channels with two different convergence angles of 3.81o and 11.31o. The ANSYS-CFX software and k-e turbulence model is used to solve Reynolds Averaged Navier-Stokes (RANS) equations. The results of the numerical modeling were then compared to the experimental data on non-prismatic compound channels with the same convergence angles. The study shows that, more or less, the k-e turbulence model is capable of predicting the velocity and boundary shear stress distributions along the flume fairly well, especially for convergence angle of 3.81o. Also by increasing relative depth, discrepancy between numerical and experimental data decreases. The results of modeling show that the k-e turbulence model is able to predict secondary flow circulations in the main channel, created by the mass exchange between the floodplains and the main channel.