水库下游冲刷的数值模拟——模型的构造

Numerical Simulation of Degradation Downstream of a Reservoir——Model Framework

由于水库下游冲刷过程中悬移质与推移质、推移质与河床质、河床质与悬移质交换机理及床沙粗化机理的复杂性,使得研究水库下游冲刷数学模型的难度较大。 为了研究水库下游冲刷、河床演变问题及由此而引起的对防洪、航运等造成的影响,本文建立了一维全沙数学模型,模型考虑了非均匀悬移质不饱和输移、非均匀沙推移质输移及床沙级配的调整。文中考虑了冲刷过程中挟沙能力的沿程调整,挟沙能力包括以下三个方面,即悬移质中细颗粒部分从累计效果看不参予与床沙交换(冲泻质),这部分泥沙全部计入挟沙能力;悬移质的粗颗粒部分落淤到床面与床沙交换后部分地计入挟沙能力;床沙中可悬浮部分从床面冲起后部分地计入挟沙能力。非均匀沙推移质输沙率公式考虑了床沙运动的随机性及床沙粗化对输沙率的影响。床沙级配的调整采用CARICHAR混合层模型。对计算中经常遇到的关键性问题提出了处理方法。

To research into the problem about degradation and fluvial process downstream of reservoirs and Us influence on flood control and navigation, a 1-D total load mathematical model was established in this paper. The non-equilibrium transport of non-uniform suspended load, the non-uniform bedload transport and sorting of the bed material are considered in the model.The adjustment of sediment-carrying capacity along the distance during degradation was considered in this paper. The sediment-carrying capacity are composed of three parts. The finer material does not exchange with the bed material from total results and is taken into account in the sedimnent-carrying capacity. The coarser material of the suspended load deposites to the bed surface and exchanges with the bed material and is partially taken into account in the sediment-carrying capacity. The suspended material of the bed material is eroded from the bed surface and partially reckoned in the sediment-carrying. The probability of movement of the bed material and effects of armoring of the bed material are considered in the formula of non-uniform bedload transport capacity. Techniques are suggested for some questions in calculations, such as, the various principle of roughness during degradation, sediment recovery coefficient in non-equilibrium suspended load equation, the thickness of the mixed layer, bifurcation and confluence of main and branch channel, the distribution of deposition and erosion along the cross section.