滩地植被化全动床复式河槽河床自适应演变机制研究

In the vegetated compound channel, the vegetation can affect the flow patterns and vortices, and then affect the sediment transport and fluvial process. Applying the theories of fluid mechanics, mechanics of sediment transport and fluvial processes, the applicants will investigate the interaction between the flow, floodplain vegetation and channel evolution with the variations of vegetation pattern and upstream sediment supply. The modification mechanism between the bed morphology and vegetation pattern variation will be elucidated. Through the flume experiment and theoretical analysis, the longitudinal variation of flow patterns will be obtained, and the effect of floodplain vegetation on the channel resistance will be clarified. The method for estimating the longitudinal distribution of streamwise velocity will be proposed in the vegetated region. The motion of the vertical vortex around the vegetation canopy and the motion of the horizontal vortex in the mixing region will be obtained using the tracer experiment. The quantitative relation between the vortices and the turbulence intensity will be proposed. The key factor for changing the position and range of sediment deposition will be clarified. These breakthroughs will perfect and update the theory, concept and method of the study on the vegetated compound channel with mobile bed. Meanwhile, the achievements of this project will enrich the research contents of river dynamics and bed morphology, and will provide the theoretical supports for the river training, river environmental restoration, and the bank protection by vegetation, etc.

在滩地有植被的复式河道中，植被特性影响滩槽水流和漩涡特性，进而改变泥沙输运和河床演变过程。申请课题以流体力学、泥沙运动力学和河床演变学等理论为基础，研究滩地植被属性及上游泥沙补给变化条件下全动床复式河槽的水流-滩地植物-滩槽演变的相互作用和内在关联，揭示复式河槽河床形态与植被特性变化的自适应演变机制。通过水槽试验和理论分析，获取水流各项特性的沿程变化规律，阐明滩地植被对床面阻力的影响，建立滩地植被区流速纵向分布的计算方法；采用示踪剂获取淹没植被顶端和掺混区的漩涡运动轨迹和作用范围，指出漩涡与紊动强度激增的定量关系；阐明滩地植被区控制推移质沉积位置和范围的关键植被因素。申请课题成果将实现滩地植被化复式河槽河床演变研究在理论、机理和方法上的创新和完善，同时将丰富水力学及河流动力学的研究内容，为河道整治、河流生态修复、植被防冲护岸等提供理论支持。

本项目以河流生态修复、植被防冲护岸和河道冲淤整治为主要应用目标，开展滩地植被化全动床复式河槽水沙运动及河床演变研究，揭示复式河槽河床形态与植被属性变化的自适应演变机制。项目通过水槽试验与理论分析，首先在不同滩地植被条件下，详细测量滩地植被区的水流各项特性，探讨了滩地植被区流速和紊动强度在水流方向及横向的变化过程，建立了植被区流速纵向分布计算方法；其次获取了滩地淹没植被垂向漩涡和掺混区横向漩涡的运动轨迹和作用范围，揭示了漩涡对泥沙运动及河床形态的影响；之后探讨了滩地植被区的泥沙输移模型，将植被属性与河床演变建立关系，搞清滩地有植被的全动床复式河槽河床自适应演变机制；最后，探究了河道内串联排列的生态浮床最佳分布方式，确定了生态浮床最有效去除有机物的排列间距。研究成果可以为河道整治、河流生态修复、植被防冲护岸等提供理论支持，实现滩地植被化复式河槽河床演变研究在理论、机理和方法上的创新和完善，丰富水力学及河流动力学的研究内容。