Mathematical model on grain-size distribution in suspension over sand-gravel bed

In this study, the grain-size distribution in suspension over a sand-gravel bed in an open channel turbulent flow is investigated from theoretical point of view. On the basis of diffusion equation, a model on grain-size distribution is developed incorporating the effect of stratification and hindered settling due to increased suspension concentration. The hydrodynamic diffusion related to particle–particle interaction is considered in the computation of reference level and the influence of incipient motion probability, non-ceasing probability and pick-up probability of the sediment particles are considered in the computation of reference concentration. Due to inclusion of several factors, the proposed model predicts well the grain-size distribution of suspended load when compared with the experimental data and also shows its prediction superiority with respect to other existing models.