题目 Title

Effects of Submerged Flexible Vegetation on Scalar Transport in an Open-Channel Flow.

期刊 Journal

Water Resources Research (IF=5.4)

作者 Author

Wang JY; He GJ; Huang L; Dey S; Fang HW

摘要 Abstract

Scalar transport in vegetated flow plays an important role in natural river ecology. In this study, a scalar transport model for the flow with flexible submerged vegetation is developed. The turbulent structure and scalar transport characteristics in the flow without vegetation, and with rigid and flexible vegetation are compared. The results show that the scalar diffusion in the flow is mainly governed by the turbulent diffusion outside the diffusion boundary layer. The wake flow downstream of rigid vegetation and the small-scale Kelvin-Helmholtz (KH) vortices near the top of the canopy are the main reasons to enhance the turbulence intensity in the flow and to significantly increase the turbulence diffusion of scalars. However, the flexible vegetation movement induces the large-scale KH vortices near the top of the canopy. It also causes to increase the turbulence intensity in the flow, to redistribute the scalar concentration in a wide range, to increase the scalar concentration across the flow depth, and to increase the scalar turbulence diffusion intensity. In the flow with rigid vegetation, the values of the turbulent Schmidt number vary from 0.72 to 1.93 below the top of the canopy, while in the flow with flexible vegetation, they vary from 0.58 to 1.99 only near the top of the canopy. Above the top of the canopy, the Schmidt number ranges from 0.48 to 0.84. The results are useful for the parameterization of scalar transport in natural vegetated rivers.

简介 Brief introduction

植被水流中的标量输运在天然河流生态中发挥着重要作用。本研究构建了柔性沉水植被水流的标量输运模型，比较了无植被水流、有刚性植被水流和有柔性植被水流的湍流结构和标量输运特征。结果表明，流动中的标量扩散主要受扩散边界层外的紊动扩散控制。刚性植被下游的尾流和冠层顶部附近的小尺度Kelvin-Helmholtz（KH）涡是流动中湍流强度增加和标量紊动扩散显著增加的主要原因。然而，柔性植被的运动会在冠层顶部附近诱发大尺度 KH 涡。它还会增加流动中的湍流强度，在较大范围内重新分配标量浓度，在整个流动深度上增加标量浓度，并增加标量的紊动扩散强度。在有刚性植被的水流中，湍流Schmidt数在冠层顶部以下在0.72到1.93的范围内变化；而在有柔性植被的水流中，仅在冠层顶部附近在0.58到1.99的范围内变化。在冠层顶部以上，Schmidt数在0.48 到0.84的范围内变化。这些结果能够用于天然植被河流中标量输运的参数化。

扫码关注立方体公众号，实时追踪课题组最新科研进展