Suspended-load transport

Abstract

The mode of sediment transport where the sediment particles are surrounded by the fluid over an appreciably long period of time is known as suspended-load transport. This chapter introduces basic concepts of sediment suspension and formulations to predict the suspended-load transport rate. The introduction of advection–diffusion model made a considerable progress in deriving the distribution of sediment concentration in sediment-laden flows. Diffusion in turbulent flow results in exchange of momentum and suspended sediment particles between layers of the flow. When the terminal fall velocity of sediment is slow enough, the sediment particles go in suspension. The suspended-load transport rate is readily computed from the known vertical distributions of sediment concentration and flow velocity. Also, based on the energy concept, gravitational theory was developed to determine the distribution of suspended sediment particles. The work done per unit time of a unit volume of fluid and suspended sediment mixture is to transfer from a layer to another layer of the flow. The conservation of energy is preserved separately in the fluid and sediment phases by balancing the energy supplied and the energy dissipated. The effects of suspended load on velocity distribution, von Kármán constant, turbulence characteristics are also discussed in details. Further, the findings on the response of turbulent bursting to sediment suspension are detailed. The computation of suspended-load transport is exemplified through worked out problems.