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

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 degrees and 11.31 degrees. The ANSYS-CFX software and the k - epsilon 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 - epsilon 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 degrees. In addition, by increasing relative depth, discrepancy between numerical and experimental data decreases. The results of modelling show that the k - epsilon 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. (C) 2018 Sharif University of Technology. All rights reserved.