Spatial distribution of deposition within a patch of vegetation
Spatial distribution of deposition within a patch of vegetation
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DOI：
10.1029/2010wr009516
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发表时间：
2011-03
影响因子：
5.4
通讯作者：
Lijun Zong;H. Nepf
中科院分区：
文献类型：
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作者：
Lijun Zong;H. Nepf
本实验室研究描述了沉积的空间格局中观察到的一个补丁的植被位于一个通道的墙壁。有两个来源的泥沙通量的补丁：平流的颗粒在上游前缘和横向分散的颗粒从邻近的明渠。这两种供给的相对贡献决定了斑块净沉积的空间格局。我们定义的平流长度尺度内补丁的纵向距离，平流贡献了显着的沉积物源。在距前缘的平流长度尺度内的距离处，斑块中的净沉积横向均匀，反映了输送颗粒的横向均匀平均流。在距离前缘比平流长度尺度更远的距离处，净沉积在平行于流动的边缘附近最高，并减少到斑块中，这是斑块边缘分散输送的特征。两个过程有助于横向分散，这两个过程都与在补片和通道之间的流动平行界面处形成的剪切层涡有关。涡流产生湍流，并增强沉积物穿过界面的湍流扩散。此外，涡流在补片内的流场中引起波振荡，这似乎增强了补片内的横向输送。
This laboratory study describes the spatial pattern of deposition observed in a patch of vegetation located at the wall of a channel. There are two sources of sediment flux to the patch: the advection of particles across the upstream leading edge and the lateral dispersion of particles from the adjacent open channel. The relative contribution of these two supplies determines the spatial pattern of net deposition in the patch. We define the advection length scale within the patch as the longitudinal distance over which advection contributes a significant sediment source. At distances from the leading edge that are within the advection length scale, net deposition in the patch is laterally uniform, reflecting the laterally uniform mean flow delivering the particles. At distances farther than the advection length scale from the leading edge, the net deposition is highest near the flow‐parallel edge and decreases into the patch, which is the signature of dispersive transport from the patch edge. Two processes contribute to the lateral dispersion, both of which are associated with the shear‐layer vortices formed at the flow‐parallel interface between the patch and the channel. The vortices generate turbulence and enhance the turbulent diffusion of sediment across the interface. In addition, the vortices induce a wave oscillation in the flow field within the patch that appears to enhance the lateral transport inside the patch.