FLOW STRUCTURE OF PARTLY VEGETATED OPEN-CHANNEL FLOWS WITH EELGRASS  

作　　者：WANG Chao YU Ji-yu WANG Pei-fang GUO Peng-cheng 

机构地区：[1]Key Laboratory of Integrated Regulation and Resource Department on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098, China [2]State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Nanjing 210098, China [3]College of Environmental Science and Engineering, Hohai University, Nanjing 210098, China [4]Yellow River Engineering Consulting Co. Ltd., Zhengzhou 450003, China

出　　处：《Journal of Hydrodynamics》2009年第3期301-307,共7页水动力学研究与进展B辑（英文版）

基　　金：supported by the National Basic Research Program of China (973 Program, 2008CB418203);the National Natural Science Foundation of China (Grant No. 50709009);the Elitist Support Project of Ministry of Education (Grant No. NCET-07-0254)

摘　　要：Aquatic vegetation can influence the transport of sediment and contaminants by changing the mean velocity and turbulent flow structure in channels. It is important to understand the hydraulics of the flows over vegetation in order to manage fluvial processes. Experiments in an open-channel flume with natural vegetation were carried out to study the influence of vegetation on the flows. In a half channel with two different densities of vegetation, the flow velocity, Reynolds stresses, and turbulence intensities were measured using an Acoustic Doppler Velocimeter （ADV）. We obtained velocity profiles in the lateral direction, Reynolds stresses in the vertical direction, and the flow transition between the vegetated and non-vegetated zones in different flow regimes. The results show that the streamwise velocity in the vegetated zone with higher density is almost entirely blocked. Reynolds stress distribution distinguishes with two different regions： inside and above the vegetation canopies. The turbulence intensities increase with increasing Reynolds number. The coherent vortices dominate the vertical transport of momentum and are advected clockwise between the vegetated zone and non-vegetated zone by secondary currents （a relatively minor flow superimposed on the primary flow, with significantly different speed and direction）, generated by the anisotropy of the turbulence.Aquatic vegetation can influence the transport of sediment and contaminants by changing the mean velocity and turbulent flow structure in channels. It is important to understand the hydraulics of the flows over vegetation in order to manage fluvial processes. Experiments in an open-channel flume with natural vegetation were carried out to study the influence of vegetation on the flows. In a half channel with two different densities of vegetation, the flow velocity, Reynolds stresses, and turbulence intensities were measured using an Acoustic Doppler Velocimeter （ADV）. We obtained velocity profiles in the lateral direction, Reynolds stresses in the vertical direction, and the flow transition between the vegetated and non-vegetated zones in different flow regimes. The results show that the streamwise velocity in the vegetated zone with higher density is almost entirely blocked. Reynolds stress distribution distinguishes with two different regions： inside and above the vegetation canopies. The turbulence intensities increase with increasing Reynolds number. The coherent vortices dominate the vertical transport of momentum and are advected clockwise between the vegetated zone and non-vegetated zone by secondary currents （a relatively minor flow superimposed on the primary flow, with significantly different speed and direction）, generated by the anisotropy of the turbulence.

关 键 词：open channel aquatic vegetation velocity profile turbulence characteristics 

分 类 号：O42[理学—声学] X524[理学—物理]