平面二维河床变形的数值模拟

Numerical Simulation of 2-D River-bed Deformation

为了研究河道平面二维的河床变形问题,及由此而引起的对防洪、航运等造成的影响,本文给出了非均匀沙的平面二维全沙动床数学模型方程组,并考虑了悬移质不饱和输移、非均匀沙推移质输移及床沙级配的调整。 在求解水流泥沙运动方程时,采用控制体积法(SIMPLEC程式)及动边界技术,对水流速度场、悬移质浓度场及河床变形进行了数值模拟。该模型采用正交曲线网格来克服天然河道边界形状复杂、长宽尺度相差悬殊以及由于水位波动引起计算边界变化等困难。通过水流、泥沙运动及河床变形的计算,给出了水位、流速、悬移质含沙量及其级配、床沙级配变化以及河床各冲淤部位的变化,并用实测资料对计算结果进行了检验,检验结果表明,计算的水位、流速、涨水期的淤积过程及落水期的冲刷过程均与实测值吻合较好。

To research on the problem about the river-bed deformation and its influence on flood control and navigation, the 2-D non-uniform total load mobile-bed 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 were considered.The control volume method(SIMPLEC) and movable boundary technique were used in solving the equations of water and sediment movement. The velocity field, the concentration field of the suspended load and the river-bed deformation were simulated. Computational difficulties in natural rivers, such as complicated boundary figures, its variation due to fluctuating of water level, great disparity between width and length of computational domain, etc. could be overcome by the presented model. Through the calculation of water and sediment movement, and river-bed deformation, the water level, the flow velocity, the concentration of the suspended load and its size-distribution, the size-distribution of the bed material, the position of erosion and deposition of the river-bed are obtained. The model was tested by the data of derformation from Zhichen to Zhijian on the Yangtze River. The calculated results show that the water level, the flow velocity, the erosion, deposition discharge and the distribution along the cross section were in close agreement with the field results.