Applicability of Euler-Lagrange coupling multiphase-flow model to bed-load transport under high bottom shear

Abstract

Bed-load transport at high shear stress is numerically simulated with the aid of the two-phase flow model, in which Euler-Lagrange coupling of the governing equations of the fluid and sediment phases are implemented. Fluid phase is described by the vertically two-dimensional k-e turbulence model in unidirectional flow condition, while the sediment motion is expressed by the numerical tracing of the saltating particles. The fluid/particle interaction, as the main interaction mechanism, is explicitly introduced into the governing equations in the present model. The characteristics of the mean-flow velocity profile of the saltation dominant flow, namely two-layer profile, is reproduced well with the present model. Experimental results show the existence of the three-layer type velocity profile under the high bottom shear, while the present model cannot reproduce such characteristics. The limitation of the assumption in the present model by neglecting the existence of the interparticle collision will be discussed on the basis of the results of the simulation.