Mixture Theory for Suspended Sediment Transport

The transport of suspended sediment in a turbulent flow is examined through the continuum theory of mixtures. Turbulent averaging, applied to the mixture momentum balances, yields a correlation representing the effect on the particles of the drag associated with velocity fluctuations in the fluid. This correlation balances the buoyant weight of the sediment in a plane uniform mean flow. Thus, classical results for turbulent diffusion of particles may be reinterpreted as models for this correlation, and the source of the diffusion process is clearly identified in view of the dynamics of fluid-particle interaction. This viewpoint leads to a multi-layer model for the mass transport in a turbulent boundary layer and results in a significant improvement in the accuracy of predicted concentration profiles in steady plane flows.