RESEARCH ON A TWO-DIMENSIONAL HORIZONTAL FLOW AND SEDIMENT NUMERICAL SIMULATION OF BRAIDED REACH

摘要

The natural branching rivers have characteristics of irregular geometrical boundary, complex topographical condition and incapable of being defined hydraulic factor, so it is difficult to make precise numerical simulation of flow and sediment transportation, and at the mean time, it requires higher standard of numerical method. As a simulation of a branch river, flow and sediment mathematical model plays an important role in quantitatively predicting the transportation of flow and sediment and the evolution of river bed. With the development of calculation speed, memory and chip number of computer, flow and sediment mathematical model has developed rapidly and also different calculation methods have emerged. Among them, the finite element method can simulate irregular geometric form quite well by using triangular grids. Therefore it can be adopted in simulating the flow and sediment in natural branching river. Based on triangular grids, the planar two-dimensional flow and sediment mathematical model in natural branching river has been established by using the finite element method. Since the mass concentration and pre-estimated and verified iteration are used to solve the equations, the question of memory units and calculating speed are settled quite well. The simulation carried out on Tianxingzhou reach of the Yangtze River shows that the results are closely fitted with the field data, which proves the model is creditable, and also the research findings can provide technical support for research on the natural branching river regulation.