TWO-PHASE FLOW MODELLING FOR SEDIMENT TRANSPORT WITH GRANULAR-MATERIAL MODEL

摘要

A two-phase flow model is presented for the simulation of sediment transport at high bottom shear stress with focusing on characteristics of the movable bed layer. The model is constructed with Euler-Lagrange coupling of fluid and sediment phases. The flow phase is computed by solving the Reynolds Averaged Navier-Stokes (RANS) equation in conjunction with the k-ε turbulence model. The sediment transport is described as the motion of a granular material under the action of steady flow, on the basis of the Distinct Element Method (DEM), with accounting for the very frequent interparticle collision of the moving particles at the hyper-concentrated layer. The characteristics of the mean-flow velocity on a movable bed are well reproduced by the present model, and the internal structure of flow is discussed based on the result of the flow turbulent properties. In addition, the characteristics of mean velocity profile of sediment phase is studied and discussed in light of the interphase momentum transfer. Finally, the model result as movable bed transport has been compared with the result of the single-particle-motion model of irregular successive saltation over fixed bed.