河流交汇区水流紊动特性与污染物输运机理研究

River confluences are important control points for mixing transportation and enrichment of water pollution. The environmental management at river confluences increasingly becomes the focus and hot spot of public attention. However, owing to the complexity of flow structure, strong turbulent flow and the specificity of river-bed form at river confluences, the mechanisms of pollutant transport have been not very clear. Therefore, in many aspects it is great significance to study on the turbulent structures of complex river-bed and the mechanisms of pollutant transport, for instances, investigation of pollutant trajectory and the end-result, management of water pollution and channel, and protection of aquatic ecological environment. Based on the methods of combination theoretical analysis, field and laboratory test with numerical analysis, hydraulic field, pollutant concentration field, pollutant trajectory and region of influence will be studied. The evolution law between pollutant distribution and flow elements will be verified. The coupling mechanism between turbulent structure of flow and pollutant transportation will be analyzed. The mesoscopic mechanics mechanism of pollutant diffusion and transportation will be revealed. These research results will have important scientific significance and application value for the development and management at river confluences as well as the development of economic and social.

河流交汇区是水体污染混合和输移富集的重要控制点，其治理日益成为社会环境治理的焦点和热点之一。然而，河流交汇处水流结构复杂、紊动强烈、床面形态特殊，污染物输运机制尚不清楚。因此，研究河流交汇区复杂河床水流紊流结构及污染物输运机制对明确河流污染物输移轨迹和归宿、治理河道水体污染、保护水生态环境均具有重要意义。本项目基于理论分析、现场与室内试验和数值分析相结合的方法，研究河流交汇区水动力场、污染物浓度场及污染物运动轨迹、影响范围；探究污染物分布和水流运动要素的演化规律；明确河流交汇区污染带分布与水流要素之间的响应关系；辨析水流紊动结构与污染物输运的耦合机制；揭示污染物迁移扩散的细观力学机制。研究成果对于河流交汇区的开发治理与经济社会发展具有重要的科学意义和应用价值。

河流交汇区是河流系统中典型的地貌单元，两股水流在此汇聚，相互顶托掺混，产生复杂而特殊的水流结构、地形形态、物质混合过程和水环境特征，对河网系统的水系连通、航运、泥沙及污染物输运和河床演变等至关重要。然而，河流交汇处水流结构复杂、紊动强烈、床面形态特殊，污染物输运机制尚不清楚。本项目按照原定计划，结合国内外研究最新动态，综合运用理论分析、室内试验、数值模拟和现场实测的方法，探究了交汇区水面形态、流场结构、水流分区、紊动特性、河床形态等水动力学特征与污染物时空分布、影响范围、混合速率、混合度等污染物输运规律；揭示了交汇角、动量比、宽深比及浓度差对交汇区水流结构和污染物输运的影响机制；构建了多沙河流交汇区水流结构与河床形态概念模型；明确了交汇区污染物混合速率、混合度与交汇条件之间的定量响应关系；揭示了交汇区水流结构与污染物输运机理。研究结果丰富了河流交汇区的流体动力学与污染物输运相关知识，对于河流交汇区的开发治理与经济社会发展具有重要的科学意义和应用价值。