Three-dimensional Numerical Simulation Of Flow And Sediment Transport In Open Channel Bend

In nature,the river bend is universal,and the bended and straight sections are the basic elements of the river.The rule of the ideal bended flow and sediment movement is the theoretical basis for studying the flow and sediment movement in natural rivers.The traditional method to study the flow and sediment movement of the bend is to use the similarity criterion to obtain a certain scale physical model test.Although the physical model test itself has many advantages,but there are also many shortcomings.With the development of science and technology,especially the progress of computer technology,numerical simulation has become an important method for the study of the flow and sediment movement law of the bended channel and has been widely used.The bended flow and sediment movement has its own unique boundary conditions and geometric characteristics.Due to the existence of centrifugal force,the flow appears a phenomenon of ultra-high water surface in the bend,resulting in a radial pressure difference.Under the action of centrifugal force and radial pressure difference,the curved channel flow produces a characteristic motion-bend circulation movement.The flow in the bend presents a complex three-dimensional spiral flow motion.Due to the presence of a circular circulation,the lateral transport of sediments was induced,resulting in the erosion and deposition characteristics of the bank on the concave side of the bend and on the side of the convex bank.In this paper,the hydraulic characteristics and sediment transport in the bend are analyzed theoretically,and the influence of the curvature of the bend on the hydraulic characteristics and sediment transport in the bend is described.This paper uses the hydrodynamic module and sediment transport module in MIKE3 to perform three-dimensional numerical simulation.The control equations of the hydrodynamic model are the continuity equation and the momentum conservation equation,and are closed by the k-? turbulence model.Only the transport operation of the bed load is considered in the sediment transport model.The sediment transport model only considers the transport operation of the bed load.Through three-dimensional numerical simulation of six bends with a certain width of the channel and bends of 30°,60°,90°,120°,150°,and 180°,and the simulation results of hydraulic characteristics and river bed erosion are obtained: The curvature not only affects the horizontal aspect ratio and surface water level,but also affects the change of the average velocity of the bottom layer.The change of the vertical and horizontal velocity and the change of the circulation position are also affected by the degree of curvature;Changes are also affected by the degree of curvature.According to the changes of the hydraulic characteristics and riverbed erosion and siltation affected by the bending degree,the effect of the bending degree on the hydraulic characteristics and river bed erosion was summarized.