稳态风沙流中瞬态输沙特征

风沙流中沙粒运动在来流风速不变时也会表现出非稳态特征。在风洞内利用粒子图像测速系统（PIV）测量了风沙运动的时间序列，并基于PIV测量技术提出风沙流中沙粒平均直径、数密度、平均水平速度和输沙通量等参数在某一时刻的计算方法，其中输沙通量的计算考虑沙粒大小垂向分布的影响。结果表明：来流风速不变时，沙粒平均直径、数密度、平均水平速度和输沙通量随时间具有明显的波动性；沙粒平均直径和平均水平速度的标准偏差一般随高度增加而增加，沙粒数密度和输沙通量标准偏差随高度增大而减小；这些参数的相对标准偏差均随高度增加而增大。

Characteristics of instantaneous sediment transport in steady aeolian sand transport

In aeolian sand transport, the movement of sand particles shows unstable characteristics even though the freestream wind speed is constant. In this paper, the sand movement over a period of time is measured by PIV (particle image velocimetry) in wind tunnel. Then the calculated method of instantaneous parameters such as mean particle diameter, particle number density, mean horizontal particle velocity and sand flux are also proposed based on the PIV technology, in which the vertical distribution of mean particle size is considered for the calculation of sand flux. The results show that when the freestream wind speed is constant, the time series of mean particle diameter, particle number density, mean horizontal particle velocity and sand flux show an obvious fluctuation. The standard deviations of mean particle diameter and mean horizontal particle velocity increase with increasing height, while the standard deviations of particle number density and sand flux decrease with height. The relative standard deviations of these parameters increase with increasing height.