Flow Analysis of Compound Channel with Non Homogenous Roughness

Abstract

Generally the natural channel consists of a wider and rougher floodplain than the main channel. Therefore the flow velocity in floodplain subsection is slower than the velocity at its main section. Due to this difference in velocities between faster moving main channel flow and slower moving floodplain flow, a relative drag and pull is created which gives rise to momentum transfer mechanism, which is called “kinematics effect”. This effect is responsible for decreasing the overall rate of discharge for over bank flow in straight compound channel. Experiments are carried out to compute the velocity as well as boundary shear along the wetted perimeter of a straight compound channel to quantify the momentum transfer along the expected interfaces originating at the junction region between main channel and floodplain. The boundary shear stress distribution is not uniform over the wetted perimeter of uniformly or non-uniformly roughened channel section. Therefore, investigation which deals with the effect of differential roughness on the flow characteristics is essential. In the present work, experiments have been done in two differential roughness conditions of compound channel having width ratio of 2.923 to analyse the stream wise velocity at different points along the lateral direction, boundary shear stress on the wetted perimeter, prediction of flow parameters. The results have been found well validated with the results obtained from 3D numerical software ANSYS (Fluent).