对风沙输运中起跳沙粒运动状态分布的讨论

本文用Lagrange方法结合起跳沙粒初始运动状态分布模拟了稳态风沙输运过程。根据已有的对地表沙粒撞击起跳现象的研究成果,列出四种典型的沙粒起跳初始运动状态分布形式。将在各分布形式下模拟得到的宏观量与风洞实验测量得到的宏观量的变化规律相比较,通过考察依据各分布形式所作数值模拟得到的风沙宏观运动的特征量与实验测量结果的一致程度,得到了其中较合理的分布形式。分析表明稳定风沙输运中起跳沙粒的初始速度和角度的分布曲线均应为一单调下降曲线,根据实验数据本文构造出由指数分布和正态分布组成的分段函数形式来描述这一曲线。并通过进一步的实验验证了这一分布形式的合理性。

ON THE PROBABILISTIC DISTRIBUTION OF INITIAL EJECTION STATE OF PARTICLES IN EQUILIBRIUM SAND TRANSPORT

The equilibrium sand transport is simulated by Lagrange model combined with the probabilistic distributions of initial speed and angle of ejection sand grain in this paper. Five forms of the possible distributions are summarized from the previous study results published in literature. Since the macro-quantities simulated by rational distribution should be coincident well with experimental result, the rationality of the distributions can be tested by comparing the quantities simulated from these distributions with the experimental quantities. Detailed analysis indicates that the distribution of initial speed and angle of ejected grains in equilibrium sand transport should be a monotonous decline function. According to the experimental data a segmented function comprised by an exponential distribution and a normal distribution is suggested in this paper. This distributions is confirmed by further comparison with experimental data.