The flux profile of a blowing sand cloud: a wind tunnel investigation
The flux profile of a blowing sand cloud: a wind tunnel investigation
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DOI：
10.1016/s0169-555x(02)00170-8
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发表时间：
2003-01-15
期刊：
影响因子：
3.9
通讯作者：
Wang, XM
中科院分区：
文献类型：
--
作者：
Dong, ZB;Liu, XP;Wang, XM
风沙云的通量廓线，即风沙通量随高度的变化，是风沙粒子沿不同轨迹运动的反映，也是检查流沙的依据。在这里，我们报告的风洞结果的系统测试的通量剖面不同大小的沙子在不同的自由流，风速。结果表明，在60 cm近地层内，风沙通量随高度的衰减可用指数函数表示：q（h）= aexp（- h/B），其中q（h）为高度h处的风沙输送率，a和B为随风速和沙粒粒径变化的参数。定义了该函数中系数a和B的意义：a表示真实蠕变下的输沙率，B表示风沙输沙率随高度的相对衰减率。真正的蠕变分数，在表面上输送的沙子（h = 0）的总输送量的比例变化很大，随着沙子的大小和风速下降。通过在对数尺度上绘制输沙率q（h），将通量剖面转换为直线。代表输沙率随高度的相对衰减率的直线的斜率随着自由流风速和沙粒粒径的增加而减小，这意味着随着沙粒粒径和风速的增加，相对更多的风沙被输送到更高的高度。平均跃移高度代表的50%的累积通量的百分比发生的高度增加与风速和粒度，这意味着跃移变得更加强烈的粒度和/或风速的增加。(C)2002 Elsevier Science B. V.保留所有权利。
The flux profile of a blowing sand cloud, or the variation of blown sand flux with height, is the reflection of blown sand particles that move in different trajectories, and also the basis for checking drifting sand. Here we report the wind tunnel results of systematic tests of the flux profiles of different sized sands at different free-stream, wind velocities. The results reveal that within the 60-cm near-surface layer, the decay of blown sand flux with height can be expressed by an exponential function: q(h) = aexp(- h/b), where, q(h), is the blown sand transport rate at height h, a and b are parameters that vary with wind velocity and sand size. The significance of coefficient a and b in the function is defined: a represents the transport rate in true creep and b implies the relative decay rate with height of the blown sand transport rate. The true creep fraction, the ratio of the sand transported on the surface (h = 0) to the total transport varies widely, decreasing with both sand size and wind speed. The flux profiles are converted to straight lines by plotting sand transport rate, q(h), on a log-scale, The slope of the straight lines that represents the relative decay rate with height of sand transport rate decreases with an increase in free-stream wind velocity and sand grain size, implying that relatively more of the blown sand is transported to greater heights as grain size and wind speed increase. The average saltating height represented by the height where 50% of the cumulative flux percentage occurs increases with both wind speed and grain size, implying that saltation becomes more intense as grain size and/or wind velocity increase. (C) 2002 Elsevier Science B.V. All rights reserved.