Multiscale wind velocity fluctuation and complex inertial response of sand saltation to wind variations give rise to intermittent and nonuniform sand transport, which greatly challenges the prediction of transport rate under wind conditions around saltation threshold. In this paper, three‐dimensional sand saltation within simulation domain of wind tunnel scale is modeled based on large eddy simulation of turbulent wind. Special attention is paid to the prediction of surface shear stress and consequently aerodynamic entrainment. When the wall stress model considering the influence of large‐scale turbulent structures was employed in case of relatively small resistance level for calculating particle aerodynamic entrainment, the model results predict sand transport below the impact threshold. The sand transport rate in this regime increases exponentially with mean wall stress, in contrast to the standard power law‐like behavior above the impact threshold. Aerodynamic entrainment and strong transport events lag behind high‐speed fluids sweep on a large scale even in wind tunnel, but the spatiotemporal variability of small‐scale sand transport is still unclear and quite complex due to transport inertia.

中文翻译：

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表面应力波动对阈值附近盐分砂运移的影响

沙质盐分对风变化的多尺度风速波动和复杂的惯性响应导致了间歇性和非均匀性的沙质输运，这极大地挑战了在盐分阈值附近的风条件下输运速率的预测。本文基于湍流的大涡模拟，对风洞尺度模拟域内的三维砂盐化进行了建模。要特别注意表面剪切应力的预测，以及因此引起的空气动力学夹带。当在考虑较小阻力水平的情况下采用考虑大型湍流结构影响的壁应力模型来计算颗粒空气动力夹带时，该模型结果预测了在冲击阈值以下的砂子迁移。在这种状态下，砂的输运速度随平均壁应力呈指数增长，这与高于冲击阈值的标准幂律行为相似。即使在风洞中，空气动力学夹带和强烈的运输事件仍落后于高速流体的大规模扫掠，但由于运输惯性，小规模沙土运输的时空变异性仍不清楚，并且相当复杂。