沙障地表形态衍化数值模拟方法研究

Numerical Method of Surface Morphology Evolution of Sand Barrier

提出了一个风沙相互作用数值模型,该模型以概率统计理论为基础,通过计算不同地表风速下沙粒的风蚀与沉积概率来实现风-沙相互作用过程,最后通过动网格技术,改变下边界节点坐标,实现沙床表面的起伏变化。数值计算与野外沙障凹坑的测量结果对比表明,沙障内地表形态的数值计算结果与实测地表形态较为接近,凹坑最低点位置向下风向一侧移动,误差最大位置为凹坑的最低点处,t=4 d时,平均绝对误差为17.86%,随着积沙增加,误差逐渐减小,t=8 d时,平均绝对误差为8.52%。所提模型无论从定性还是从定量上,都与野外测量结果较为一致,可以正确模拟沙障地表的发展过程。

A new numerical model of sand-wind interaction was proposed to predict the surface morphology evolution and provide the basis for dimension design of sand barrier. Based on the theory of probability and statistics,the model realized sand-wind interaction process by calculating wind erosion and deposition probability of sand grains at different wind speeds. Firstly,the model parameters of air phase and sand phase were initialized,and the velocity distribution can be calculated by computational fluid dynamic（ CFD） method. Secondly,the wind friction velocity of sand element was calculated by using velocity field data,and the sand transport rate can be obtained. Finally,the thickness of sand element was calculated by calculating sand change in one time step. The moving mesh technique was used to change the fluctuation of the sand bed by changing the coordinates of lower boundary nodes. The numerical results were compared with the measured results,which showed that the numerical results of the surface morphology in the sand barrier were close to the measured results. The lowest point of pit was the maximum position that moved along the downwind area,the average absolute error was 17. 86% when t = 4 d,the error was decreased gradually with the increase of sand accumulation,the average absolute error was 8. 52% when t = 8 d. Both qualitative and quantitative results were consistent with the measured results,and the model can simulate the surface morphology evolution of sand barrier correctly.