Modeling multi-scale turbulent dispersion in two-phase dilute flows

Abstract:

For sediment transport in turbulent dispersed multiphase flows, turbulent dispersion causes sediment particles to be transported from high concentration regions to low concentration regions and determines the concentration distribution of suspended sediment. In this study, we present a new turbulent dispersion model for large-scale dilute flows with suspended sediment. Three time scales are considered in the model: particle response time, fluid turbulence time scale, and Kolmogorov time scale. Two Stokes numbers are defined using these three time scales: one for large eddies and the other for small eddies. The new turbulent dispersion model considers the effects of both large-scale and small-scale (Kolmogorov-scale) eddies on turbulent dispersion by parametrizing Schmidt number using these two Stokes numbers. The new model is validated against experimental data available for flows with suspended sediment in open channels under a wide range of conditions for two-phase dilute flows.