干支流汇合处的二维河床变形数值模拟

为了做好汇流处的河道规划，定量地预测出汇流处的河床变形情况是很重要的．本文建立了一个既能处理干支流汇流，又能考虑泥沙粒度分布以及流线曲率的二维河床变形数学模型，并通过两个算例对汇流处的河床变形以及粒径分选情况进行了讨论．在算例1中，干支流的泥沙粒度分布被设定为相同，在算例2中，支流的泥沙被设定为比干流的细小，其平均粒径为干流的一半．计算结果表明，汇流处的冲淤情况两计算例子基本相同，受支流河床泥沙组成的影响不大，但汇流处的河床平均粒径，却深受支流来沙的影响，两算例差异较大．当支流泥沙细小时，受其直接流入影响，汇流处左岸未呈现出冲刷与河床粗化的对应关系．

Two Dimensional Numerical Simulation for River Bed Variation at Confluence

River bed variation forecasting is a very important issue in the work of river channel planning, especially in the planning work at the confluence. This paper presents a two dimensional model to simulate the river bed variation situation at the confluence of branch and main river, the model may consider not only the sediment sorting effect but also the difference between streamline curvature and channel curvature. Two calculation cases are employed to discuss the river bed variation and sorting conditions at the confluence. In the first calculation case,the sediment condition of branch is same as that of main river, while in the second calculation case, the sediment of branch is finer, its mean grain size is only the half of that of main river. The calculation results indicate that the erosion and deposition situations of two cases are similar and only effected slightly by However, the mean grain size at confluence is the sediment condition variation in branch. effected largely and appears quite different between two cases. When the sediment in branch is fine, the corresponding relationship between erosion and sediment coarsening can hardly be seen at the left bank of confluence, due to the fine sediment transportation from branch to confluence.