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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Reynolds stress and sand transport over a foredune
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Reynolds stress and sand transport over a foredune

机译：雷诺应力和砂岩在前缘上的运输

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Reynolds shear stress (RS=-u′ w′) and sand transport patterns over a vegetated foredune are explored using three-dimensional velocity data from ultrasonic anemometers (at 0·2 and 1·2m) and sand transport intensity from laser particle counters (at 0·014m). A mid-latitude cyclone on 3-4 May 2010 generated storm-force winds (exceeding 20ms~(-1)) that shifted from offshore to obliquely alongshore. Quadrant analysis was used to characterize the spatial variation of RS quadrant components (Q1 through Q4) and their relative contributions were parameterized using the flow exuberance relation, EX_(FL)=(Q1+Q3)/(Q2+Q4). The magnitudes of RS and sand transport varied somewhat independently over the dune as controlled by topographic forcing effects on flow dynamics. A 'flow exuberance effect' was evident such that Q2 (ejection-like) and Q4 (sweep-like) quadrants (that contribute positively to RS) dominated on the beach, dune toe, and lower stoss, whereas Q1 and Q3 (that contribute negatively to RS) dominated near the crest. This exuberance effect was not expressed, however, in sand transport patterns. Instead, Q1 and Q4, with above-average streamwise velocity fluctuations (+u′), were most frequently associated with sand transport. Q4 activity corresponded with most sand transport at the beach, toe, and stoss locations (52, 60, 100%). At the crest, 25 to 86% of transport was associated with Q1 while Q4 corresponded with most of the remaining transport (13 to 59%). Thus, the relationship between sand transport and RS is not as straightforward as in traditional equations that relate flux to stress in increasing fashion. Generally, RS was poorly associated with sand transport partly because Q1 and Q4 contributions offset each other in RS calculations. Thus, large amounts of transport can occur with small RS. Turbulent kinetic energy or Reynolds normal stresses (u′~2, w′~2) may provide stronger associations with sand transport over dunes, although challenges exist on how to normalize and compare these quantities.
机译：利用超声波风速计（在0·2和1·2m处）的三维速度数据和激光粒子计数器的沙子传输强度，研究了雷诺兹剪切应力（RS = -u'w'）和植被带上沙的传输模式。在0·014m）。 2010年5月3-4日的中纬度气旋产生风暴力风（超过20ms〜（-1）），从海上转移到倾斜的沿海。象限分析用于表征RS象限分量（Q1至Q4）的空间变化，并使用流量旺盛关系EX_（FL）=（Q1 + Q3）/（Q2 + Q4）参数化其相对贡献。在沙丘上，RS和沙的迁移量在一定程度上独立地变化，这受地形对流体动力学的影响所控制。明显的“流量旺盛效应”使得Q2（喷射状）和Q4（扫描状）象限（对RS产生正向影响）在海滩，沙丘脚趾和较低的底部占主导地位，而Q1和Q3（对象限较高对RS负）在波峰附近占主导地位。但是，这种旺盛的效果并未在沙粒的运输方式中体现出来。取而代之的是，Q1和Q4具有高于平均水平的水流速度波动（+ u'），最常与砂的运输有关。第四季度的活动对应于沙滩，脚趾和草丛位置的大多数沙子运输（52％，60％，100％）。在波峰处，运输的25％至86％与第一季度相关，而第四季度与其余的大部分运输相对应（13％至59％）。因此，沙流与RS之间的关系并不像传统方程式那样简单，传统方程式将通量与应力相关联，且关系不断增加。通常，RS与沙的运输联系不佳，部分原因是Q1和Q4贡献在RS计算中相互抵消。因此，小的RS可能会发生大量的传输。湍流动能或雷诺法向应力（u'〜2，w'〜2）可能与沙丘上的沙运输有更强的联系，尽管在如何规范和比较这些量方面存在挑战。

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