Numerical Simulation Of Hydrodynamics And Water Quality Of The Typical Reaches And Reservoirs In Ningxia Of The Yellow River

This dissertation takes the Daliushu-Shapotou section with continuous bends and the Yazidang Reservoir with complex terrain as the research object.Based on RNG k-? turbulence mathematical model,2D and 3D numerical simulations are carried out based on the measured results.This paper studies the flow movement,sediment transport,river bed deformation and water quality convection-diffusion on these two typical research objects.Firstly,the image stitching algorithm,edge detection algorithm combined with CAD software and Google Earth software are used to detect the waterfront edge accurately.The longitude and latitude information of the study area is obtained efficiently,and the terrain file is generated by programming with the measured elevation information.Secondly,the Delaunay triangulation mesh of the initial terrain is carried out by Bowyer-Watson algorithm.The irregular triangular mesh model TIN is constructed,and the irregular triangular mesh is generated from discrete elevation points to realize terrain interpolation of triangular mesh after mesh division.Thirdly,a 3D mathematical model of flow-sediment-water quality and a 2D mathematical model of flow-sediment-water quality are established.The governing equations of the mathematical model are written into a unified general form by transient terms,convection terms,diffusion terms and source terms.On this basis,the governing equations are discretized by using five formats in the FVM.The discrete governing equations are solved by using the SIMPLEC algorithm based on the unstructured grid combined with the under-relaxation technique.The GMRES algorithm is used to solve the discrete equations with initial conditions and boundary conditions.Finally,the RNG k-? turbulence mathematical model of the Daliushu-Shapotou section and the Yazidang Reservoir is validated.The 2D and 3D flow movement and bed deformation of the Daliushu-Shapotou section under four conditions are carried out.The 2D numerical simulation of flow movement and 3D numerical simulation of water quality convection and diffusion in the Yazidang Reservoir under four types and eight working conditions are carried out.After analyzing the measured elevation and sediment particle size of the Daliushu-Shapotou section,the simulated values of plane flow field,section flow field,lateral flow velocity and bed deformation are compared with the measured values,and the results are in good agreement.Based on the measured data,the flow movement and bed deformation are carried out.The results show that the flow field,sediment transport and bed deformation will change according to the difference of inlet discharge,suspended sediment concentration,k value,? value and outlet water level.After analyzing the measured bottom elevation,the contour line and the three-dimensional topography of the Yazidang Reservoir,the simulated values of flow field and average vertical velocity of section of the reservoir are compared with the measured values,and the results are in good agreement.Based on the measured data,the flow movement is carried out.The results show that the flow field and flow velocity in the reservoir are controlled by the inflow,intake,wind speed and wind direction.After sampling and analyzing seven water quality indexes near the intake tower of the Yazidang Reservoir,the simulated values of CODCr and TN concentration distribution in the reservoir are compared with the measured values,and the results are in good agreement.Based on the measured data,the numerical simulation of water quality convection and diffusion in the reservoir is carried out.The results show that the distribution of water quality concentration in the reservoir is changed by the inflow,intake,wind speed and wind direction,initial concentration distribution of water quality in the reservoir,and the inflow water concentration.The above research results provide technical support and theoretical basis for the study of water and sediment transport law and water environment control of similar continuous bends and similar reservoirs.