Numerical simulation of aeolian dusty sand transport in a marginal desert region at the early entrainment stage

摘要

Aeolian dusty sand transport in the marginal region of a desert is described numerically from first suspension motion at the early entrainment stage to the unsteady state within a moderate range (1000 m long × 500 m high). A two-dimensional model is built for wind-blown dust flow, and the calculations are carried out using Fluent software. The simulation results describe an integrated picture of aeolian dusty sand transport including uplift, suspension, diffusion, deposition and its space-time concentration. According to the features of a sand-dust storm near the surface, a volume concentration expression of ejection grains is developed as a boundary condition in the simulation approach. The model is verified by comparing results with both experimental data from a wind tunnel and an analytic solution. Uniform dust sizes and R-R distributions are used in the simulation. Gas-solid two-phase flow patterns with these grains are obtained in the downwind space, including the turbulence intensity, gas phase stream functions and solid volume concentration distributions. The influence of wind velocities and grain sizes is analyzed. From the simulation results, spatial distributions of dust volume concentration in the early entrainment stage are described clearly. Different from coarse sands, there is a clear band of uniformly saturated dust concentration in the region directly above the surface.