稳态风场下的沙粒运动规律

The characteristic of sand movement in windblown sand movement

风沙运动是风沙地貌以及土壤侵蚀的主要原因,跃移运动是风沙运动的主要形式,跃移沙粒占整个运动沙粒的75%左右,这一运动不仅是沙量传输的主要运动形式,也是造成沙质地表风蚀和风沙灾害的根本原因.通过数值模拟的方式研究了当风沙运动达到稳定状态时的风沙流运动特征,详细讨论了稳态情况下沙粒的跃移运动规律,以期对防沙治沙工作能起到一定的指引.研究结果表明:在不同的初始风速条件下,当风沙运动达到稳定状态时在高度小于10倍的沙粒直径处的风速基本相同,这是由于地表风场被运动沙粒强烈修正,有效粗糙度随着摩阻风速的增加而增加;同时在给定的风场风速下,跃移轨迹和碰撞速度并不是无限增大的,而是存在最大的跃移轨迹和最大的碰撞速度,并且最大碰撞速度以及最大跃移轨迹的高度和长度与摩阻速度成线性关系.

Windblown sand movement is responsible for aeolian landforms,deflation and soil erosion.The saltation movement is the main form of windblown sand movement,it accounted for about 75%,which is not only a major sport in windblown sand movement,but also the reason of erosion.The windblown sand movement in steady and it＆#39;s characteristic were discussed in detail,in order to be play on anti -desertification.The results showed that the wind speed in the reptating layer varies little at the different frication velocities,the wind in the steady state is modified by the sand grains in the air,and the effective roughness increases with the increase of friction velocity;Simultaneously,saltation trajectory and impact velocity is bounded,the maximum saltation trajectory and the maximum impact velocity present in a given wind speed;And the maximum impact speed and the maximum saltation height and length of tracks has a linear relationship with the friction.