考虑颗粒群阻力效应的跃移运动

Effects of particle swarm on saltation of wind-blown sand flow

考虑到风沙流中颗粒群阻力效应,采用修正后的单球模型阻力系数公式,计算了跃移运动达到稳定状态时的风速廓线、输沙量、沙粒相体积分数.结果表明:当跃移达到稳定状态时,考虑颗粒群阻力效应对阻力系数修正时计算所得的输沙量、沙粒相体积分数均大于不修正时的相应值.当摩阻风速增大时,输沙量及颗粒相体积分数也会随之增大,而以相同速度起跳的颗粒跃移长度随之增大,高度有所降低.

Most studies on wind-blown sand flow use the standard drag coefficient formula for single sphere particle to deal with sand movement in saltation,failing to think about the particle swarm effect when more and more grains move together.A modification of the drag coefficient by grains＇ volume density was introduced in this paper and was then used to calculate the mass flux,wind speed profile and grains＇ volume density in steady state of wind-blown sand movements.The numerical results show that both mass flux and grains＇ volume density calculated with the modified model were larger than those calculated by the standard model,but the wind speed was insensitive to this kind of modification.In addition,with the friction velocity being increased,the mass flux and grains＇ volume density increased as well.This means that the effect of particle swarm on saltation is of importance and should be considered in further study.