沉水植被斑块对风生流型浅水湖泊水流影响研究

Wind-induced current is the dominant hydrodynamic process in shallow lake in China. The transportation of substance and water quality pattern are closely related to the wind-induced current. Most of the shallow lakes in China grow aquatic plants, and submerged plants are the main species of the aquatic plants. Submerged aquatic plants change the lake hydrodynamic process, and further change the processes of transportation of substance and water quality pattern. Therefore, the relationship between the flow characters of wind-induced current and aquatic plants becomes an important research topic of shallow lake hydrodynamics in our country. This project uses prototype submerged herbaceous plant often found in shallow lakes and riparian wetlands as test materials and carry out experiment in the wind tunnel flume to explore the hydrodynamic characters of wind-induced current, the mechanism of interaction between submerged herbaceous plant patch and wind-induced current. The results from this research would provide theoretical base for controlling water turbidity, distribution of nutrients, pollutants and ecological restoration of damaged ecology. Numerical modeling together with field survey and indoor experiments is the main tool for investigating ecological remediation engineering of river, lake and riparian wetland. Therefore, this project will develop a three dimensional numerical model which will include the interaction phenomena between submerged herbaceous plant patch and wind-induced current. This model will also be verified with the experimental results from this project.

风生流是我国浅水湖泊的主导水动力过程，湖泊的物质输运和水质状态与风生流密切相关。我国浅水湖泊中多生长水生植物，沉水植物是其中的主要物种，沉水植物的存在改变了湖泊的水动力过程，进而改变了物质输运和水质状态。因而，湖泊风生流的流动特性及其与水生植物的关系就成了我国浅水湖泊水动力和生态研究的一个重要组成部分。本课题以国内浅水湖泊、滨河湿地常见的原型沉水草本植物为对象，利用风洞水槽进行试验，分析风生流的水动力特征和沉水草本植物斑块与风生流的相互作用机理，为控制湖泊水体浊度、营养盐和其他污染物质的分布，恢复受损生态，提供理论基础。数值模拟配以现场观测和实验室典型试验，是当前研究河道、湖泊、滨海湿地生态修复工程的主要手段。为此，本课题拟引入含沉水植被斑块水槽试验分析得到的阻力系数、紊动特征尺度等成果，建立含柔性沉水植物斑块的风生流的三维数值模型，并利用本课题试验成果对建立的数学模型实用性进行验证。

风生流是我国浅水湖泊的主导水动力过程，湖泊的物质输运和水质状态与风生流密切相关。我国浅水湖泊中多生长水生植物，沉水植物是其中的主要物种，沉水植物的存在改变了湖泊的水动力过程，进而改变了物质输运和水质状态。因此，湖泊风生流的流动特性及其与水生植物的关系就成了我国浅水湖泊水动力和生态研究的一个重要组成部分。本项目的研究目的是阐明湖泊水生植被覆盖区清水形成的机理，以期指导湖泊湿地大型水生植物修复和湿地水质净化工程实践。本项目以国内浅水湖泊、滨河湿地常见的沉水植物苦草为对象，利用风洞水槽进行试验，分析风生流的水动力特征和沉水草本植物斑块与风生流的相互作用机理。试验发现风生流的表面水体流速都是顺风向、为正的风生流，而下部水体流速则都是与风向相反、为负的补偿流。沿着整个水槽，风生流的大尺度垂向环流结构是存在的。还发现风生流沿垂直方向是一个周期性的运动过程，其周期和风生表面波的周期接近。风生流中增加了植物使得水流结构更加复杂，下扫流将水体中的泥沙携带至近底层，泥沙在底部喷射流态的作用下，水流能量降低，促使泥沙顺利着床淤积。数值模拟配以现场观测和实验室典型试验，是当前研究河道、湖泊、滨海湿地生态修复工程的主要手段。本项目利用大涡模型，模拟了含柔性沉水植物斑块的风生流，且得到了较好的模拟结果。