风应力驱动下湖湾水流结构及污染物运动特性的数值模拟研究

Bay is the forefront area to be ecological damaged and repaired with complicated hydrodynamic and water environment, which is the relatively small and enclosed area in the lake. Natural conditions, wind-driven circulation patterns is the the main movement form. Therefore,researching on flow structure under wind-driven and transportation of pollutants in the bay of lake is the key to improve the technology of ecological restoration in bay. Currently, numerical simulation method is the main method to study of hydrodynamic and transport in lakes. Two-dimensional or quasi three-dimensional mathematical model are usually used to research the flow and transport phenomenons in lake, which is difficult to accurately describe the spatial flow pattern and combining the trajectory characteristics of dissolved pollutants. In the project, we focus on the Calculation of complex flow and transport phenomenons in lakes, and use the two-dimensional hydrodynamic model, three dimensional numerical model for gas-liquid two-phase flow model and Lagrangian Particle-tracking method to research the the influence between the wind stress and the flow in different type's bay. Further more, research the function mechanism of flow in the bay which role by wind field, study the flow structure of the typical bay, the concentration of pollutants, the dissolved substance trajectory. Finally building a vectors relations between the wind field, flow field and the concentration field of the pollutant.

湖湾作为湖泊中相对狭小和封闭的区位，是生态破坏与修复的前沿阵地，其水动力与水环境异常复杂。自然条件下，风生流是湖湾水体的主要运动形式，故揭示风应力驱动下湖湾水流结构及污染物运动特性是提升湖湾生态修复技术的关键。当前，数值模拟方法是研究湖泊水动力及污染物运动的主要手段。国内外大多采用二维或准三维数学模型研究湖泊平面分层风生流及其污染物迁移扩散特性，尚难以准确描述湖湾空间流态以及非溶解态污染物运动轨迹。项目围绕风应力驱动下湖湾水体及污染物复杂的运动特征，通过二维水动力模型、水气两相流全三维数值模拟、拉格朗日粒子追踪等方法，研究风应力对不同类型湖湾水动力从形成到稳定过程的影响，分析风场对湖湾流场的作用机制，探究典型湖湾风生流空间流场及结构、污染物时空变化、非溶解态物质运动轨迹等，构建自然条件下湖湾风场-流场-污染物浓度场的矢量映射关系，为湖湾水环境修复与河湖连通水质调度提供理论依据和技术支撑。

湖湾作为湖泊中相对狭小和封闭的区位，是生态破坏与修复的前沿阵地，其水动力与水环境异常复杂。自然条件下，风生流是湖湾水体的主要运动形式，揭示风应力驱动下湖湾水流结构及污染物运动特性是提升湖湾生态修复技术的关键。本项目通过对长江流域与淮河流域的87个湖湾形态调查，选取面积、形态系数和开敞度作为湖湾分类指标，给出了湖湾类型的概化公式。采用数值模拟的方法定量分析了风力驱动下概化湖湾风场-流场-污染物浓度场三者间的矢量映射关系。主要成果包括：（1） 针对自然界湖湾形态差异较大的现状，调研了湖湾地理特征资料，筛选了表征湖湾地理特征的重要指标，即面积、形态系数和开敞度，依据指标对湖湾进行分类，界定类别界限，并推导了将真实湖湾概念化为矩形湖湾的公式。（2）采用湖湾水动力水质数值模型，模拟了不同形态湖湾的二维流场与示踪剂浓度场，以湖湾平均流速、污染物浓度等为指标，系统研究了湖湾自然属性对湖湾湖流及湖湾水体交换能力的响应规律。（3）在上述研究基础上，模拟研究了不同风向作用下湖湾环流的形成过程以及风速与湖湾平均流速、水体交换率间的定量关系。