非均匀沙输移数值模拟关键问题研究

As an important means to study the sediment transportation, numerical simulation plays a pivotal role in the researches for region and river basin sediment problems, as well as the engineering and environmental sediment problems. As a result, the inadequacy of the researches for the key issues in the numerical simulation for non-uniform sediment transportation will seriously restrict the reliability of the outcome, when the numerical simulation was taken as the main research method. At present, the disputes of the key issues in numerical simulation for non-uniform sediment transportation among scholars, and the differences among the outcome of the studies carried out on the sediment problems in some great water control projects, and the current measured data, show that the key issues in numerical simulation for non-uniform sediemnt transportation need to be further and deeply studied. This research is planned to do deep explorations on the properties and the inner mechanism of the non-uniform sediment transport on the basis of the current study. And based on the kinetic theory and sand wave movement, further studies will be carried out on the rise and mixing for non-uniform sediment particles in the near-bed flow layer, and the vertical distribution of sediment concentration under non-equilibrium state condition. After that, the key issues in the numerical simulation for non-uniform sediment transport, such as the non-uniform sediment carrying capacity, sediment recovery saturation coefficient and the thickness of the mixed bed layer will be studied. This study will improve the accuracy of the numerical simulation for non-uniform sediment transportation, as well as to broaden the non-uniform sediment transport theories and to promote the development of the sediment disciplines, which would provide a theoretical basis and technical support for the great water conservancy project construction and the river training works.

数值模拟作为研究泥沙输移的重要手段，在区域及流域泥沙、工程及环境泥沙等问题的研究中发挥着举足轻重的作用，其关键问题研究的不足将严重制约以此为手段的相关研究成果的可靠性。目前，众多学者对非均匀沙输移数值模拟中某些关键问题的争论，以及当前对某些大型水利枢纽工程泥沙问题的数值模拟预测成果之间及其与当前的实际观测成果之间存在的差异都表明，非均匀沙输移数值模拟中的某些关键问题还有待于进一步的深入研究。本项目拟在当前研究的基础上，基于动理学理论和沙波运动理论，对非均匀沙运动特性及输移机理进行进一步的深入探讨，对河床非均匀沙上扬及掺混、非平衡输沙状态含沙量沿垂线分布等基本问题进行进一步研究，在此基础上对非均匀沙挟沙力、恢复饱和系数及混合层厚度等数值模拟中的关键问题进行研究，提高非均匀沙输移数值模拟计算的精度，拓宽非均匀沙输移理论，推动泥沙学科的发展，为重大水利工程建设及河道治理等提供理论依据和技术支持。

数值模拟作为研究泥沙输移的重要手段，在区域及流域泥沙、工程及环境泥沙等问题的研究中发挥着举足轻重的作用，其关键问题研究的不足将严重制约以此为手段的相关研究成果的可靠性。目前，众多学者对非均匀沙输移数值模拟中某些关键问题的争论，以及当前对某些大型水利枢纽工程泥沙问题的数值模拟预测成果之间及其与当前的实际观测成果之间存在的差异都表明，非均匀沙输移数值模拟中的某些关键问题还有待于进一步的深入研究。本项目在当前研究的基础上：①考虑非均匀河床泥沙颗粒间的相互隐蔽与暴露作用、不同含沙量水平下近河床底部泥沙颗粒间的相互碰撞作用及其对泥沙上扬与沉降的影响及不同水沙条件、河床边界及泥沙颗粒特性对近河床底部泥沙沉降的影响，基于动理学理论，推导了泥沙上扬理论公式，并在此基础上了建立了非均匀沙挟沙力计算公式；②在分析非平衡输沙条件下非均匀沙恢复饱和系数随泥沙特性、冲刷历时与距离以及河床边界条件的变化规律的基础上，基于动理学理论建立非平衡调整系数计算公式以完善非平衡输沙条件下的含沙量沿垂线分布求解，从而计算非均匀沙恢复饱和系数；③基于沙波运动过程中河床上的泥沙与水体中的泥沙相互交换及掺混的物理机制，考虑混合层厚度范围内非均匀沙的掺混及交换与沙波运动过程的相关性及比拟关系，建立了基于沙波运动的混合层厚度计算方法。本项研究能提高非均匀沙输移数值模拟计算的精度，拓宽非均匀沙输移理论，推动泥沙学科的发展，为重大水利工程建设及河道治理等提供理论依据和技术支持。