Boundary Shear Stress Distribution in Curved Compound Open Channels

An analytical model for evaluation of boundary shear stress in compound open-channel bends is developed. Perpendicular volumetric elements are generated in all cross sections of a bend. Each element represents an equation with two parameters, including the secondary current parameter and momentum transfer coefficient, accounting for acceleration and internal forces. For each cross section with N elements, N equations with N unknowns of streamwise depth-averaged velocity are derived. The boundary shear stress distribution is then calculated using the Darcy-Weisbach relationship. The momentum transfer coefficient is related to the geometric characteristics of the channel cross section and the bend. The present results were compared with the experimental data available in the literature. The experimental models have trapezoidal and rectangular main channels with both curved and straight paths. The results seem to be acceptable except at the interface of the main channel and floodplains, because of the planform vortices. Overall, the total results are satisfactory, and the present analytical model can be used to predict the boundary shear stress in simple and compound channels. (C) 2020 American Society of Civil Engineers.