Two-Dimensional Numerical Simulation Of Water And Sediment Movement And Fluvial Process In Curved And Bifurcated Channels

Curved and bifurcated channels is quite common in alluvial plain,and it differs with single straight river because it has two branches at least.What’s more,the movement of water and sediment is very complex and the primary and secondary branches change alternately with the deformation of riverbed,which bring navigational conditions many uncertainty factors.This paper establishes a two-dimensional mathematical model of curved and bifurcated channels based on the numerical simulation software-MIKE to study the law of the movement of water flow,riverbed’s deformation focusing on the studying object-Yaojian river and other typical curved and bifurcated channels in the middle reach of Yangtze river,and predicts the evolution trend of curved and bifurcated channels in a long time period.The main content of this paper is listing as follows:1.After setting up a two-dimensional mathematical model of typical curved and bifurcated channels according to a large number of measured morphology data,this paper selects some representative formulas to verify the reliability of the generalized model,and the validation includes the horizontal surface slope,the longitudinal velocity distribution and the maximum scour depth of the bend.Then calculation of the generalized mathematical model calculation is done based on the designed working condition which has 7 kinds of fixed bed conditions and five kinds of movable bed conditions.Finally this paper analyzes the movement of water and sediment and the law of riverbed’s deformation of typical curved and bifurcated channels.Part of the results in this paper show that: Water level and velocity distribution are both complex in branching area of curved and bifurcated channels,but at the same time,distribution of water level and velocity are quite different in each branch.The intensity of circulation in the inlet and outlet boundaries are quite large,which makes the big elevation changes of the terrain of central island’s head and tail.The results of the study have universal applicability due to the extensive samples,and can be applied to other models of bending and braided river and channel regulating engineering.2.In order to verify the reliability of mathematical model of Yaojian river based on the measured data,a validation is made to test the mathematical model for the fixed-bed during flood,medium and dry seasons and for riverbed’s deformation during a year and a half time because of the river erosion.This paper uses the preliminary design of theThree Gorges hydropower station from 1961 to 1970,that is to say,10 years of water and sediment conditions for sediment reduction after processing the inlet boundary condition of the mathematical model of Yaojian river and uses the fitting curve of the outlet boundary water level and the inlet boundary flow to calculate the water level conditions of the outlet boundary for simulating calculation in 20 years.Finally this paper analyzes the movement of water and sediment and the law of riverbed’s deformation and predicts the deformation of riverbed and sedimentation trend during a long time period.It is concluded in this paper that the right branch continues to be the the primary branch of Yaojian river for a long time,and the left branch has a tendency to shrink or even to be blocked.These results of this paper has certain reference value in reaching this river’s regulation schemes.