混合沙跃移运动数值模拟

Numerical simulation of mixed sand saltation

采用数值模拟方法分析了混合沙的跃移运动规律,模拟结果表明:模型能够合理反映混合沙实际跃移行为,模拟结果与野外试验和他人实验结果基本相符;混合沙跃移输运主要集中于地表之上30cm以下,达总输沙量95%以上;总输沙率垂向分布整体呈指数规律递减,靠近地表处形成输沙率峰值;不同粒径沙粒输沙率随高度的变化与总输沙率基本一致,但是各粒径输沙量、输沙率峰值大小、峰值所处的高度各不相同;风速的增大并不改变混合沙和各粒径沙粒输沙率垂向分布的结构形式,只是风速增高,输沙率峰值和峰值所处的高度均增大;随着风速的增大,总输沙量中小粒径沙粒份额逐渐降低,大粒径沙粒份额逐渐升高。

The movement regulation of mixed sand saltation was analyzed by numerical simulation method.Results showed that the model could reflect the actual mixed sand saltation behavior,simulation results were basically consistent with field experiments and others experimental results.Mixed sand saltation transport mainly concentrated on 30cm above sand bed,with more than 95% of the total sand mass flux,vertical profile of the total sand transport rate exponentially decreased,the peak of sand transport rate was formed near sand bed.Vertical profiles of different size sand transport rate were consistent with the total sand transport rate,but the mass flux,transport rate peak size,peak height of each sand size were different with each other.The transport rate vertical profiles of mixed sand and each size sand were unaltered with wind velocity increasing,while the peak size and peak height of sand transport rate increased as wind velocity increasing,the proportion of small sand particles gradually decreased in the total mass flux,while the proportion of large sand particles increasing.