Reynolds stress anisotropy with higher-order turbulence in flow through rigid emergent vegetation: An experimental study

IF 2.4 3区 环境科学与生态学 Q2 ENGINEERING, CIVIL
Pritam Kumar, Aaditya Ojha, Anurag Sharma
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引用次数: 0

Abstract

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.

具有高阶湍流的雷诺应力各向异性通过刚性植被的实验研究
实验研究了直通道中有裸露刚性植被的光滑刚性床上流动的湍流和雷诺应力各向异性。分析了高阶湍流,如湍流扩散率、三阶速度脉动矩、象限分析和湍流动能通量。利用植被和非植被条件下的特征值,通过各向异性不变图(AIMs)研究了雷诺应力各向异性。在植被区,扩散率更高,速度的明显降低会在外层产生更大的涡流;而在非植被区,近床层有较大的旋涡形成。基于速度波动的相对迹象进行了象限分析,这表明当水流从非扰动区域进入植被区时,雷诺剪切应力从床面传递到自由面。植被区床面附近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。尽管如此,非植被区床面附近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AIMs来理解,AIMs表示非植被区的轴对称膨胀,而植被区的轴向对称收缩。这项研究的结果为明渠水流中植被和非植被区的湍流结构提供了重要而详细的视图。
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来源期刊
Journal of Hydro-environment Research
Journal of Hydro-environment Research ENGINEERING, CIVIL-ENVIRONMENTAL SCIENCES
CiteScore
5.80
自引率
0.00%
发文量
34
审稿时长
98 days
期刊介绍: The journal aims to provide an international platform for the dissemination of research and engineering applications related to water and hydraulic problems in the Asia-Pacific region. The journal provides a wide distribution at affordable subscription rate, as well as a rapid reviewing and publication time. The journal particularly encourages papers from young researchers. Papers that require extensive language editing, qualify for editorial assistance with American Journal Experts, a Language Editing Company that Elsevier recommends. Authors submitting to this journal are entitled to a 10% discount.
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