The shallow water flow through and around a patch of rigid emergent vegetation was investigated numerically. The mean flow field and turbulent structures were studied, especially their dependence on the solid volume fraction (SVF) of the patch and the bed friction. Two streamwise velocity scales, U_1s at the starting point of the steady wake and U_1e at the downstream end of the steady wake, and the length of the steady wake L₁ were used to describe the steady wake behind the patch. U_1s was found to be related to SVF only. However, U_1e and L₁ were influenced by both the SVF and the wake stability parameter S. For a sparse patch, U_1e was equal to U_1s, and L₁ decreased with the increase of S. For a mid-dense patch, U_1e was always smaller than U_1s, and it increased with S and gradually approached U_1s. The increase of U_1e reduced the lateral velocity difference between the flows inside and outside the wake, which resulted in the increase of L₁. For a highly dense patch, U_1e and L₁ did not increase unless S was larger than a critical value. A new parameter, r, was proposed to represent the development rate of the steady wake. The numerical results showed that r increased monotonously with S for mid-dense patches.

数值研究了浅水流过和围绕一块刚性挺水植被。研究了平均流场和湍流结构，特别是它们对补片的固体体积分数 (SVF) 和床摩擦的依赖性。两个流向速度尺度，稳定尾流起点的U _{1 s}和稳定尾流下游端的U _{1 e}，以及稳定尾流的长度L ₁用于描述斑块后面的稳定尾流。发现U _{1 s}仅与 SVF 相关。然而，U _{1 e}和L ₁受 SVF 和尾流稳定性参数S 的影响。对于稀疏块，U _{1 e}等于U _{1 s}，L ₁随着S的增加而减小。对于中等密度的斑块，U _{1 e}总是小于U _{1 s}，并且随着S 的增加逐渐接近U _{1 s}。U _{1 e}的增加减小了尾流内外流动的横向速度差，导致L₁ . 对于高度密集的补丁，除非S大于临界值，否则U _{1 e}和L ₁不会增加。提出了一个新参数r来表示稳定尾流的发展速度。数值结果表明，对于中等密度的斑块，r随S单调增加。