The wake structure behind a porous obstruction and its implications for deposition near a finite patch of emergent vegetation
The wake structure behind a porous obstruction and its implications for deposition near a finite patch of emergent vegetation
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DOI：
10.1029/2012wr012224
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发表时间：
2012-09-13
影响因子：
5.4
通讯作者：
Nepf, Heidi
中科院分区：
文献类型：
--
作者：
Chen, Zhengbing;Ortiz, Alejandra;Nepf, Heidi
本实验研究描述的平均和湍流结构的圆柱体，这是一个模型的一个补丁的紧急植被的圆形阵列的唤醒。斑块直径D和斑块密度a（每体积的正面面积）是变化的。流动结构与无因次流动阻塞参数C（D）aD有关，C（D）aD是斑块直径与阻力长度尺度（C（D）a）（-1）的比值。C-D是圆柱体阻力系数。离开补片的速度U-e相对于上游速度U-无穷大减小，并且U-e/U-无穷大随着流动阻塞（C（D）aD）增加而减小。建立了U-e/U-infinity的预测模型。补片后的尾流包含两个湍流强度峰值。第一个峰值直接发生在补丁的后面，并且与补丁内的湍流产生有关。湍流强度的第二个峰值出现在距离补丁下游L-w处，与von Karman涡街的尾流尺度涡有关。尾流中U-e的存在延迟了冯卡门涡街的形成，直到距离L-1（
This experimental study describes the mean and turbulent flow structure in the wake of a circular array of cylinders, which is a model for a patch of emergent vegetation. The patch diameter, D, and patch density, a (frontal area per volume), are varied. The flow structure is linked to a nondimensional flow blockage parameter, C(D)aD, which is the ratio of the patch diameter and a drag length scale (C(D)a)(-1). C-D is the cylinder drag coefficient. The velocity exiting the patch, U-e, is reduced relative to the upstream velocity, U-infinity, and U-e/U-infinity decreases as flow blockage (C(D)aD) increases. A predictive model is developed for U-e/U-infinity. The wake behind the patch contains two peaks in turbulence intensity. The first peak occurs directly behind the patch and is related to turbulence production within the patch at the scale of individual cylinders. The second peak in turbulence intensity occurs at distance L-w downstream from the patch and is related to the wake-scale vortices of the von Karman vortex street. The presence of the flow U-e in the wake delays the formation of the von Karman vortex street until distance L-1 (