基于床面泥沙三维暴露度的非均匀泥沙输移规律研究

Bed load sediment transport is an important subject of river dynamics. However, there are three flaws in the current study on bed load sediment transport rate: The theoretical foundation of sediment transport law is not perfect in the absence of quantitative analysis of all movement forms of the moving particles; sediment incipient motion standard were treated as deterministic problem, which did not reflect sediment continuous starting condition and probability; the random distribution of sediment on bed surface is mainly based on the two-dimensional exposure test and the theoretical hypothesis by Han Qiwei, which is not perfect..In this research, the self-designed instrument to measure particle position, 3 d laser scanner, PIV and ADV velocity measuring system, high speed camera, particle fluctuating pressure sensing system, large test flume with variable slope will be used to investigate 3-D distribution features of bed surface sediment, near wall region turbulence coherent characteristics, the pulsation force acting on the sediment particles and the process of the moving particles; and the mechanism of acting force of flow on sediment, the coupling effect between the turbulence characteristics and moving particles, and the change laws of sediment moving parameters will be presented. Finally the threshold probability formula corresponding to sediment starting state in theory will be deduced, and the formula of bed-load sediment transport rate is established considering the influence of the three-dimensional bed sediment distribution and near-bottom turbulence structure..This research will theoretically improve the research level of sediment transport law, improve the accuracy of formula calculation, and provide a solid theoretical foundation for the study of river bed evolution and regulation, reservoir and navigation engineering design.

推移质泥沙输移问题是河流动力学中一个重要课题。目前研究成果主要存在问题：缺乏对推移质各运动形式量化分析，使泥沙输移规律的理论基础不够完善；泥沙起动标准多被作为确定性问题，不能量化反映泥沙起动状态及概率；床面泥沙随机性分布主要基于韩其为提出的理论假设及二维暴露度试验观测。本项目拟采用自主设计定制的颗粒位置测量仪、3D激光扫描仪、PIV与ADV测速系统、高速照相机、水流脉动传感器、大型自动变坡水槽等测试仪器和技术，对床面泥沙三维分布规律、近底水流湍流特征、泥沙颗粒受力脉动过程及推移质运动过程观测分析；揭示床面泥沙受力机理、湍流特征与颗粒间的耦合效应、推移质运动参数的变化规律；构建泥沙起动标准与起动概率间量化指标，建立计入床面泥沙三维随机分布规律与近底湍流结构影响的非均匀泥沙输沙率公式。项目研究将从理论上提高泥沙输移规律研究水平，提高公式计算精度，为河库泥沙冲淤计算提供坚实理论基础。

非均匀沙输移规律对泥沙运动力学的理论发展和水利工程的实际应用具有重要意义。.从泥沙起动特点出发，分别以二维床面和三维床面为研究对象，重新定义了床面泥沙颗粒位置关系的量化参数，通过自行设计的试验装置，观测、统计分析了水流作用条件下均匀沙和非均匀沙床面颗粒位置量化参数的取值范围和分布规律，为研究非均匀沙起动和输移规律奠定了坚实基础。.通过均匀沙和非均匀沙水槽试验，研究了上游表层泥沙颗粒不同遮蔽距离和遮蔽粒径下的近底水流特性。此外，借助高速摄影技术，进行了非旋转和旋转圆球的沉降试验，研究了水流作用条件下泥沙颗粒受到的作用力。该研究进一步揭示了床面三维形态对近底湍流结构的影响，以及水沙相互作用条件下泥沙颗粒的受理机理。.基于泥沙起动的随机特性，以概率论与力学分析相结合的方式，建立了考虑水流条件随机性和床沙位置分布规律影响的泥沙起动概率公式，以此重新定义泥沙起动标准，构建了均匀沙和非均匀沙的起动流速公式。在此基础上，通过水槽试验，建立了低强度输沙时的均匀推移质输沙率公式，构建了同一起动标准下不同起动参数量值的对应关系。该研究丰富和拓宽了泥沙起动的随机理论。.基于高速摄像技术，观测了跃移颗粒撞击床面的过程，构建了跃移颗粒撞击模型；观测了不同床沙级配及水流条件下推移质的运动形式，确立各运动形式与其影响因素间的关系，构建了均匀沙、非均匀沙推移质平均运动速度公式。该研究进一步揭示了推移质运动的统计规律和力学机理。.基于经典推移质水槽试验实测资料，采用起动概率理论、颗粒跃移特性和非线性理论，分别建立了均匀推移质输沙率公式，其中起动概率理论的推移质输沙率公式反映了推移质各运动形式量比的影响。在此基础上，由非均匀泥沙颗粒位置关系，推求了非均匀泥沙起动概率修正系数，构建了非均匀推移质输沙率公式和推移质级配公式。该研究揭示了不同泥沙级配和水流条件下的非均匀沙推移质运动规律，可为工程实际应用提供重要的理论支撑。