Combined Impact of Density Stratification and Hindered Settling on Nonequilibrium Suspended Sediment Transport in Open Channel Flows

Abstract

The present paper studies the two-dimensional unsteady suspended sediment transport problem through an open channel turbulent flow that carries large amounts of sediments. Presence of large amounts of sediments causes separate, distinct horizontal layers that result to differences in density, which is called density stratification. Also, due to interactions with neighboring particles, a particle settles at a reduced speed relative to that of a single particle in clear fluid, which is called hindered settling. The model includes both of these effects and the governing equation, which is a nonlinear partial differential equation (PDE), has been solved by the finite difference (FD) method. The model has been validated with existing models under certain specific conditions. It is found that stratification causes a decrement in sediment concentration values and the effect becomes prominent as time increases until it reaches a stable value. A reverse result is obtained for the case of hindered settling and both the effects are visible mainly in the main suspension region. Finally, the model has been validated with a few existing models together with some experimental data at steady-state and far-field conditions.