低浓度下反弹参数对固结土壤表面沙粒跃移的影响

Effects of Rebound Parameters on Sand Saltation on Consolidated Surfaces in Very Low Density

风沙运动中跃移起着最重要的作用.跃移沙粒碰撞地表后的反弹参数决定了沙粒接下来的运动轨迹.尽管没有疏松地表跃移复杂,固结土壤表面的沙粒跃移研究并不全面.通过数值计算探究了地球、火星和金星条件下反弹参数对固结土壤表面跃移的影响.反弹参数由B 1k、A 2k和B 2k 3个参量表征,其中,B 1k反映速度恢复系数的变化,A 2k和B 2k反映反弹角度的变化.结果显示,跃移发展稳定后的4个物理量(恢复系数、入射速度、入射角度和跃移长度)对3个参量有不同的响应.相比于A 2k,4个物理量对B 1k和B 2k更敏感.在4个物理量中,跃移长度对3个参量敏感性最高.在低浓度情况下,反弹参数对固结土壤表面沙粒跃移的影响随着风速增加而减弱,因而低速跃移的沙粒应考虑反弹参数的影响.

Sand saltation plays the most important role in aeolian sand movement.The rebound parameters obtained after the collision of saltating grain with the Earth surface,are crucial for subsequent motion of the grain.Although the saltation is less complex than that on loosen surface,sand saltation over consolidated surface is still not well understood.This paper explores the influence of the rebound parameters on sand saltation over consolidated surface on three planets(Earth,Mars and Venus).The rebound parameters include three parameters(B 1k,A 2k and B 2k).B 1k reflects the variation of restitution coefficient while A 2k and B 2k reflect that of rebound angle.The simulated results reveal that all saltation-related physical quantities(restitution coefficient,incident speed,incident angle and saltation length)at a stable stage have different influence on three parameters.Compared with A 2k,these four physical quantities are much more sensitive to B 1k and B 2k.Among the four physical quantities,the saltation length shows the highest sensitivity to all the parameters.Besides,the effects of rebound parameters on sand saltation over consolidated surfaces become weaker gradually with the increase of wind strength.Hence,it is necessary and much meaningful to consider the influence of rebound parameters on sand grain with low-speed saltation.