The flow turbulence and Reynolds stress anisotropy in flow over the smooth rigid bed with the emergent rigid vegetation in a straight channel have been experimentally investigated. Higher-order turbulence such as turbulent diffusivity, third-order moments of velocity fluctuation, quadrant analysis and flux of turbulence kinetic energy have been analysed. Reynolds stress anisotropy has been investigated by Anisotropic invariant maps (AIMs) with the use of eigenvalues for both vegetation and non-vegetation condition. In the vegetation zone, more diffusivity occurs and an apparent decrease in velocity causes larger eddies in the outer layer; whereas in the non-vegetation zone, larger eddies formation at near-bed has been found. Quadrant analysis has been done based on relative signs of velocity fluctuation which signifies that Reynolds shear stress is transported from the bed surface to the free surface when flow enters in the vegetation zone from the non-disturbed region. The longitudinal distribution of the anisotropy tensor near the bed surface for the vegetation zone provides the higher anisotropic flow than those of non-vegetation zone. Although, transverse and vertical distributions of the anisotropy tensor in the vicinity of the bed surface for the non-vegetation zone provide a lower anisotropic stream. Flow anisotropy can be understood by AIMs indicating axis-symmetric expansion in a non-vegetation zone whereas axis-symmetric contraction is in the vegetation zone. The outcomes of this study deliver a significant and detailed view of turbulent flow structures in vegetation and non-vegetation zone in an open channel flow.

通过实验研究了直通道中出现刚性植被的光滑刚性河床上流的湍流和雷诺应力各向异性。对湍流扩散系数、三阶速度脉动矩、象限分析、湍流动能通量等高阶湍流进行了分析。雷诺应力各向异性已通过各向异性不变图 (AIM) 使用植被和非植被条件的特征值进行了研究。在植被区，扩散性更强，速度明显降低，导致外层涡流更大；而在非植被区，在近床处发现了较大的涡流形成。根据速度波动的相对符号进行象限分析，这表明当水流从非扰动区域进入植被区时，雷诺剪应力从床面传递到自由表面。植被区近床面各向异性张量的纵向分布提供了比非植被区更高的各向异性流量。尽管如此，非植被区床面附近的各向异性张量的横向和垂直分布提供了较低的各向异性流。流动各向异性可以通过 AIM 来理解，AIM 指示非植被区域中的轴对称扩张，而植被区域中的轴对称收缩。这项研究的结果提供了明渠流中植被和非植被区域湍流结构的重要而详细的视图。