A Numerical Simulation of Windblown Sand Movement over a Slope Surface

摘要

Current theoretical studies and numerical simulations of windblown sand movement concentrate on ideal circumstances, such as steady wind velocity, flat sand surface, etc. However, environment of windblown sand movement is complex in natural, such as complex landform, turbulence structure of wind flow. Actually gradient of windward slope of sand dune and sand ripple etc. which are basic form of desert landscape, have great influence on the initiation and transportation of sand particles. Wind velocity over slope surface is measured by using PDPA technique in wind tunnel to analyze characteristics of wind flow at windward slope and leeward slope. Here established a model of sand saltation movement where wind is coupled with sand particles to simulate windblown sand movement over a slope surface. The SIMPLE algorithm is applied to calculate wind flow and sands transportation is simulated by tracking every particle moving over slope. The results have shown that there is a reversed flow region in leeward slope, and the area become larger when the coupling effect of wind and sand particles is taken into consideration, which implies that particles have obvious effect on wind flow, especially at the leeward slope. At the windward slope, mass flux of sand particles gradually increase along the slope and change regularity of mass flux along height is different from that on flat surface although mass flux of sand particles gradually decreases with height at the windward slope. At the leeward slope, mass flux of sand particles increases first and then decrease with height at leeward slope, which is different from that at windward slope. The maximum of mass flux gradually reduces as sand flux moves away from the top of slope. This work is a preliminary study for sand flow in a complex terrain and is basic importance for study the real sand flow.