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

Abstract

In this paper, an attempt was made to study a flow field in compound channels with non-prismatic floodplains. A three-dimensional Computational Fluid Dynamic (CFD) model was used to calculate the velocity distribution, secondary flow circulation, and boundary shear stress in non-prismatic compound channels with two different convergence angles of 3.81° and 11.31°. The ANSYS-CFX software and the k - £ turbulence model were used to solve Reynolds Averaged Navier-Stokes (RANS) equations. The results of the numerical modelling were then compared to the experimental data in non-prismatic compound channels with the same convergence angles. The study shows that, more or less, the k - £ turbulence model is capable of predicting the velocity and boundary shear stress distributions along the flume fairly well, especially for convergence angle of 3.81°. In addition, by increasing relative depth, discrepancy between numerical and experimental data decreases. The results of modelling show that the k - £ 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.