Numerical Modeling of the Effect of Different Angles of Floodplain Divergence on Shear Stress Distribution and Fluid Velocity in Compound Non-Prismatic Channels

Compound channels form the cross section of many rivers, especially in adjacent areas of residential and agricultural areas. Investigation of hydraulic behavior of compound channels is of great importance in floodplain control and river management plans. In this study, by modeling a concrete compound channel with Ansys Fluent software using k-ε turbulence model and VOF method, shear stress and average flow velocity in compound channel with divergent floodplains were determined for different divergence angles. Also, the boundary conditions for flow in the studied channel are defined as input mass flow rate, output limit as pressure outlet, solid boundaries as non-slip and rough wall and upper channel boundary as non-slip and rough wall. The modeling and comparison between the laboratory data and the results of the present study showed that the maximum velocity in the channel occurs with a divergence angle of 3 degrees and with increasing the divergence angle, the flow velocity also decreases. In addition to, maximum of shear stress in the compound channel occurs with a lower divergence angle; In other words, as the divergence angle of the floodplain increases, the amount of shear stress of the fluid also decreases.