沉水植被斑块尾流多尺度紊流结构研究  

Investigation of wake flow on submerged vegetation patches based onspectral proper orthogonal decomposition

作　　者：张维乐 吴时强[2,3] 吴修锋 薛万云[2,3] 王芳芳[2] 张宇 於思瀚[2] ZHANG Weile;WU Shiqiang;WU Xiufeng;XUE Wanyun;WANG Fangfang;ZHANG Yu;YU Sihan(College of Architectural Engineering,Tianjin University,Tianjin 300072,China;Nanjing Hydraulic Research Institute,Nanjing 210029,China;Yangtze Institute for Conservation and Development,Nanjing 210098,China)

机构地区：[1]天津大学建筑工程学院,天津300072 [2]南京水利科学研究院,江苏南京210029 [3]长江保护与绿色发展研究院,江苏南京210098

出　　处：《水科学进展》2023年第6期913-927,共15页Advances in Water Science

基　　金：国家自然科学基金资助项目(52209032);江苏省自然科学基金资助项目(BK20221190)。

摘　　要：探究斑块尾流中多尺度紊流结构对理解植被群落影响下的泥沙输移规律和河床演化过程有着重要意义。通过室内水槽试验,分析不同高径比及植被体积分数影响下的斑块后水流特性,得到时均流速及雷诺应力分布规律;通过谱本征正交分解对其脉动场进行分析,探究不同尺度涡的空间模态及能量分布规律。研究结果表明:①冠层垂向剪切层内剪切强度及其最大量纲一剪切层垂向厚度随着植被体积分数增大而增大,随着高径比增大而减小。②斑块尾流中,大尺度涡旋对应频率集中在0.15~0.29 Hz,对应斯特劳哈尔数为0.16~0.32,垂向分布介于0.2~1.3倍植被高度,纵向分布介于2~6倍斑块直径,横向关于植被中心线呈现出非对称分布。③纵向出流流速及剪切层内紊动强度是影响稳定尾流区长度的重要因素。剪切层纵向输运速度随着纵向出流流速增大而增大,剪切层垂向扩散速度随着紊动强度的增大而增大。The multi-scale turbulent structures enable understanding the vegetation patch-affected sediment transport and riverbed evolution.Here,flume-based wake flow characteristics were analysed under different aspect ratios and vegetation densities.The mean flow velocity and Reynolds stress distribution were obtained.The fluctuation field was analysed using the spectral proper orthogonal decomposition to obtain different scale eddies′spatial modes and energy distribution.We demonstrate the following:①The shear strength and non-dimensional shear layer thickness increased with the vegetation density and decreased with increasing canopy shear layer aspect ratio.②The wake flow large-scale eddies exhibited a 0.15—0.29 Hz frequency and 0.16—0.32 Strouhal number(Sr).The eddies exhibited 0.2—1.3 times higher vertical distribution than the vegetation and 2—6 times wider longitudinal distribution than the patch diameter.The eddies exhibited transverse distribution from the vegetation centreline.③The wake region longitudinal outflow velocity and turbulence intensity affected the stable wake region length.The longitudinal outflow velocity and turbulence intensity determined the shear layer longitudinal transportation and vertical diffusion velocities,respectively.

关 键 词：植被斑块 多尺度紊流 沉水植被 谱本征正交分解 尾流区长度 

分 类 号：TV133[水利工程—水力学及河流动力学]