CFD Simulation of Velocity Distribution in a River with a Bend Cross Section and a Cubic Bed Roughness Shape

Abstract

The variation of bed roughness along a channel cross section especially if the cross section with bend affects the velocities in that part of the section may be used to change the flow patterns in the channel and as a mean of river training. In this research the Computational Fluid Dynamics (CFD) for modelling the effect of bed roughness on the free surface flows in open channel has been validated for a straight river, the effect of angles of attack downstream the bed roughness has been investigated. This study presents the results and analysis of numerical simulations that were carried out to compute Manning’s coefficient of artificial geometric roughness element (cubic shape). Artificial roughness elements were fixed on bed of the flume within the test section in different spacing and angles of attack. A sequence of CFD simulations using the k-ω SST model are compared with a set of laboratory data for the influence of flow at a free surface in open channel with cubic shape bed roughness. The numerical results gaining confidence in a modelling of Volume of Fluid (VOF) technique and allows for modelling of more complex hydraulic structures by including the effect of angles of attack to the simulation.