近岸植被化河道水流混合层及相干结构

For rivers with vegetation growing near the shore, studies are mostly focused on river ecological restoration and ecological river engineering practice, whereas there are few studies on whether flow and sediment characteristics are beneficial to river health and stability, if flow capacity meets the requirements of flood discharge and pollutants transport mechanism and so on. The object of this project is three typical types of offshore vegetation flow. And this project analyzes the water and sediment dynamic characteristics, revealing time-average and turbulence characteristics of flow under the joint influence of the offshore vegetation zone and secondary flow caused by cross section, sediment exchange mechanism between the vegetation zone and mainstream and the distribution of bed shear stress, in order to investigate the control effect of offshore vegetation and natural river boundary on water and sediment, which is helpful for the achievement of the stability of ecological river with offshore vegetation and the sustainable development of the river channel. Then three-dimensional hydrodynamic model and two-dimensional depth-averaged model and one-dimensional unsteady flow model based on vegetation resistance are established, forming the mathematical description of water and sediment characteristics of the offshore vegetation river. At the same time, the momentum exchange and sediment exchange between offshore vegetation belt and river mainstream are analyzed to reveal the effect of offshore vegetation belt on longitudinal dispersion. On the basis of theoretical analysis and experimental research, we will propose the theoretical description of the longitudinal dispersion of ecological river channels considering the influence of offshore vegetation zone. These results can be directly applied to ecological river design and environmental impact assessment.

对近岸植被化河道大都集中在河道生态修复、生态河道工程实践的研究。对近岸植被化河道水流泥沙特性是否有益于河流健康与稳定,过流能力是否满足行洪要求,污染物质输移机理如何等探究的较少。本项目以三种典型形式近岸植被水流为对象,研究其水沙动力学特性,揭示近岸植被带及断面形状共同形成二次流作用下水流时均和紊动特性,植被带与主流带泥沙交换机理，河床切应力分布及纵向离散特性。探究如何借助近岸植被与自然河床边界控制水沙,实现近岸植被河道的稳定健康可持续发展。进而建立描述近岸植被水流的三维水动力学模型和二维水深平均模型以及基于植被阻力的一维非恒定水流模型,以形成近岸植被河道水流特性的数学描述。同时对近岸植被带与主流带之间动量交换、泥沙交换进行分析，揭示近岸植被带对污染物纵向离散的影响。在理论分析和试验研究基础上提出近岸植被带影响下生态河道纵向离散的理论描述。成果直接服务于生态河道设计及环境影响评价。

对近岸植被化河道大都集中在河道生态修复、生态河道工程实践的研究。对近岸植被化河道水流泥沙特性是否有益于河流健康与稳定,过流能力是否满足行洪要求,污染物质输移机理如何等探究的较少。本项目以三种典型形式近岸植被水流为对象,即近岸连续植被、非连续植被和岸冰河道水流，研究其水沙动力学特性，揭示近岸植被带及断面形状共同形成二次流作用下水流时均和紊动特性,植被带与主流带动量交换机理，泥沙在植被斑中的沉积模式，河床切应力分布及纵向离散特性。探究如何借助近岸植被与自然河床边界控制水沙,实现近岸植被河道的稳定健康可持续发展。进而建立描述近岸植被水流的三维水动力学模型和二维水深平均模型以及基于植被阻力的一维非恒定水流模型,以形成近岸植被河道水流特性的数学描述。同时对近岸植被带与主流带之间动量交换、泥沙交换进行分析，揭示近岸植被带对污染物纵向离散的影响。在理论分析和试验研究基础上提出了近岸植被带影响下生态河道纵向离散的理论描述。成果直接服务于生态河道设计及环境影响评价。