底床形态对异重流分流约束机制及其水沙演化机理

It is one of main contents and scientific problems that what mechanism on turbidity current diversion constrained by bed shapes in reservoir and its flow and sediment evolutionary mechanism, which is also the main technological problem faced by the flushing predict calculation in reservoir in sediment-laden river. At present, the resistance issues involved in the mathematical equations that describe the physical process is often generalized into a comprehensive resistance which has not accurately reflected the energy loss mechanism, and is divided into on-way resistance and local resistance with the status that is weakness in theory and lack of related quantitative parameters.Therefore,this project aims in the aspect of mechanism, with flume experiments investigation, using advanced velocimeter, the channel bed shapes(triangle,trapezoid,rectangular) respectively is shifted to study the flow pattern and the dynamic mechanism where gravity current creeps. In the aspect of theory, calculation theory and methods on localized loss and turbulent kinetic energy transfer are to be built, with combined solution by water dynamics equation and energy conservation equation. In the aspect of application, according to the kinetic theory of sediment movement, transport characteristic of gravity current of sediment under different boundary conditions is to be analyzed, with the results of quantitative relationships between the key parameters and process constrained by bed shapes about localized loss, velocity shift coefficient, sediment content shift coefficient, Froude number etc. And verification is to be carried out with surveyed data in Xiaolangdi reservoir, which would lay the foundation for practical application.

底床形态对水库异重流分流的约束机制，以及底床形态对水库异重流分流的水沙演化机理是异重流输移研究的主要内容和重要科学问题，也是多沙河流水库排沙预测面临的主要技术难题。目前，对描述该内容的物理方程中涉及的阻力问题往往概化为综合阻力不能准确反映其能量损失机理，而分割为沿程阻力与局部阻力等又存在理论薄弱和相关参数缺乏的现状。因此，本项目在机理层面，通过水槽试验研究，借助于先进流速仪，改变底床形态（三角形、梯形、矩形）研究异重流分流突变段水流流态及紊动机制，揭示水流流态与局部损失的耦合机理；在理论层面，利用水动力学方程和能量守恒方程，建立紊动动能变化、局部损失计算理论与方法；在应用层面，依据泥沙运动力学理论，解析不同边界条件下异重流的输移特性，获得分流突变处异重流局部损失、流速改变、含沙量改变、佛汝德数等关键参量及过程的定量关系，并利用小浪底水库实测资料开展验证，为实际应用奠定基础。

本项目以理论探讨、水槽试验和数学模型为手段，完成了各项研究任务。现将研究成果汇报如下：（1）不同输沙流态下水库支流分流分沙机理。采用典型多沙河流水库的代表小浪底和官厅水库实测资料，分析了小浪底水库典型支流畛水和石井、官厅水库典型支流妫水的淤积变化特征，并采用拦门沙增长规模作为自变量、体积比含沙量与入库流量与形态作为因变量建立了公式，给出了不同输沙流态条件下支流分流分沙机理。（2）局部阻力损失公式。改建了现有的π型玻璃水槽，以入库流量、含沙量、横断面形态为变化因子组合了11组试验，分析了异重流运动、扩散过程规律，研究分流突变河段异重流流态变化特点，流速垂线分布变化特性；结合分流突变处水流输沙特性，研究分流处浑液面变化，含沙量垂线分布变化特性，分析了底床横断面变化对异重流分流的约束机制，提出基于底床横断面形态变化的异重流分流处局部阻力损失表达式；（3）分流分沙比理论公式。在此基础上，引入分流窗口时间，结合韩其为异重流倒灌长度公式，建立了异重流分流比、分沙比理论公式，并采用水槽试验结果进行了验证。在以上研究成果基础上，提出异重流局部损失的计算公式和支流分流量与底床形态变化表达式，以小浪底水库畛水支流库段为例模拟矩形、梯形、三角形河槽约束下支流分流后的干流含沙量的变化情况，结果表明相同过流量条件下，三角形河槽内的异重流浑液面高于梯形和矩形的，支流分流、分沙比较大。研究成果不仅丰富了河流泥沙动力学，而且为黄河调水调沙生产实践提供了技术支撑，具有重要的理论价值和实践价值。通过项目研究，获得省部级奖项1项；出版专著1部；软件著作权1项；标注期刊论文13篇，其中SCI 1篇，EI 4篇；国际会议1篇，国内核心4篇，国内会议一般期刊3篇,参加国际学术会议5人次；培养青年学术骨干3名，博士研究生2名。

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