Flow adjustment and interior flow associated with a rectangular porous obstruction
Flow adjustment and interior flow associated with a rectangular porous obstruction
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DOI：
10.1017/jfm.2011.199
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发表时间：
2011-06
影响因子：
3.7
通讯作者：
J. Rominger;H. Nepf
中科院分区：
文献类型：
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作者：
J. Rominger;H. Nepf
通过实验和标度法描述了矩形多孔障碍物前缘和内部的流动。多孔障碍物由浅水中突现的矩形圆柱体阵列组成，这种结构模仿了水生植物。流动的主要特征取决于无因次冠层流阻，这是阻塞宽度和孔隙率的函数。对于本文测试的冠层流阻范围，流体在障碍物上游以与阵列宽度成比例的长度尺度减速。对于高流量堵塞，多孔阻塞内的内部调节长度由阵列宽度设置。对于低流量堵塞，阵列的每单位体积的正面面积设置内部调节长度。在调整区域的下游，内部速度由湍流应力的横向发散和冠层阻力之间的平衡，或由压力梯度和冠层阻力之间的平衡所控制，这取决于对开尔文-亥姆霍兹（KH）涡阵列的横向渗透，这是由无量纲冠层流动阻塞设置的。对于具有两条平行流边的多孔障碍物，沿两条边的KH涡街在阵列宽度上通信：这种现象导致交叉阵列涡组织，显著增强了涡强度，并在多孔障碍物内产生了显著的横向输送。
The flow at the leading edge and in the interior of a rectangular porous obstruction is described through experiments and scaling. The porous obstruction consists of an emergent, rectangular array of cylinders in shallow flow, a configuration that mimics aquatic vegetation. The main features of the flow depend upon the non-dimensional canopy flow-blockage, which is a function of the obstruction width and porosity. For the ranges of canopy flow-blockage tested in this paper, the fluid decelerates upstream of the obstruction over a length scale proportional to the array width. For high flow-blockage, the interior adjustment length within the porous obstruction is set by the array width. For low flow-blockage, the array's frontal area per unit volume sets the interior adjustment length. Downstream of the adjustment regions, the interior velocity is governed by a balance between the lateral divergence of the turbulent stress and canopy drag, or by a balance between the pressure gradient and canopy drag, depending on the lateral penetration into the array of Kelvin–Helmholtz (KH) vortices, which is set by the non-dimensional canopy flow-blockage. For a porous obstruction with two stream-parallel edges, the KH vortex streets along the two edges are in communication across the width of the array: a phenomenon that results in cross-array vortex organization, which significantly enhances the vortex strength and creates significant lateral transport within the porous obstruction.