Impact of turbulence on aeolian particle entrainment: results from wind-tunnel experiments
Impact of turbulence on aeolian particle entrainment: results from wind-tunnel experiments
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DOI：
10.5194/acp-22-9525-2022
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发表时间：
2022-07
影响因子：
6.3
通讯作者：
J. Zhang;Guang Li;Lin Shi;N. Huang;Y. Shao
中科院分区：
文献类型：
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作者：
J. Zhang;Guang Li;Lin Shi;N. Huang;Y. Shao
摘要。我们假设大涡流在风成粒子的夹带中起主要作用。为了验证这一点，进行了风洞实验，测量了不同尺寸和流动条件下的颗粒夹带速率。风洞流通常是中性分层的，没有大的涡流，而大的涡流通常在对流大气边界层中看到。在这里，应用了一种新技术，通过部署一块随机飘扬的布，产生类似于对流涡流的大涡流，这里被称为准对流湍流。在Monin-Obukhov相似框架下，分析了中性湍流的准对流湍流特征，并检验了表面剪应力的概率分布。我们表明，在给定的平均流速下，与中性流动条件相比，准对流湍流增加了表面剪切应力并改变了其概率分布，从而大大增强了沙尘颗粒的夹带。我们的假设因此被风洞实验所证实。我们还解释了为什么大涡流对风携带和运输很重要。
Abstract. We hypothesize that large eddies play a major role in the entrainment of aeolian particles. To test this, wind-tunnel experiments are carried out to measure the particle entrainment rate for various sizes and flow conditions. Wind-tunnel flows are usually neutrally stratified with no large eddies, which are typically seen in convective atmospheric boundary layers. Here, a novel technique is applied, by deploying a piece of randomly fluttering cloth, to generate large eddies similar to convective eddies, here referred to as quasi-convective turbulence. The characteristics of quasi-convective turbulence are analyzed with respect to neutral turbulence in the Monin–Obukhov similarity framework, and the probability distributions of surface shear stress are examined. We show that for a given mean flow speed and in comparison with neutral flow conditions, quasi-convective turbulence increases the surface shear stress and alters its probability distribution and hence substantially enhances the entrainment of sand and dust particles. Our hypothesis is thus confirmed by the wind-tunnel experiments. We also explain why large eddies are important to aeolian entrainment and transport.