Estimation of diffusion coefficients, lateral shear stress, and velocity in open channels with complex geometry

The lateral distributions of depth-averaged apparent shear stress, depth mean velocity, and diffusion coefficients are essential in certain quantitative analysis for sediment transport and environmental studies. An analytical method for the computation of these parameters is presented. A mathematical relationship between these parameters, based on the concept of surplus energy transport through a minimum relative distance developed by Yang and Lim [1997], is established, the depth-averaged apparent shear stress is determined from the boundary shear stress, depth mean velocity is obtained by considering the influence of nonuniform shear velocity and the free surface in 3-D channels, and the diffusion coefficients are linked to the depthaveraged apparent shear and velocity. The theoretical formulations for the distributions of depth-averaged apparent shear stresses, depth mean velocity and diffusion coefficients in trapezoidal and compound channels are presented. Comparisons between the theoretical and the measured lateral distributions of the depthaveraged apparent shear stresses and the depth mean velocities are also presented, and a reasonable agreement is achieved.