Sediment diffusion coefficient model for predicting the vertical distribution of suspended sediment concentration in uniform open-channel flows

Abstract

This paper presents a theoretical model for predicting the vertical distribution of suspended sediment concentrations in open-channel flows. The model developed uses a new sediment diffusivity coefficient obtained by the application of the Itakura and Kishi correction method to the Kerssens sediment diffusivity profile. The new coefficient is calculated using composite operators applied to the Rouse sediment diffusivity profile. The diffusivity profile proposed increases as a parabolic profile from zero at the bottom to a maximum value in the lower part of the flow, and then decreases slowly towards the water surface without reaching zero. The maximal value is calculated at a level between 20 and 30% of the total water depth as explained previously by Coleman. Based on this diffusivity profile, a theoretical formulation for computing sediment concentration is derived analytically, using the well-known convection–diffusion equation. We compare results from the proposed model with experimental measurements and existing theoretical models, obtained by previous researchers, in order to evaluate the applicability of the present model to predict particle concentration profiles in open-channel flows. The computed values of sediment concentrations are in good agreement with the experimental data reported in the literature.