Establishment And Application Of Hydrodynamic And Water Quality Model For Yangzhou River Network

In order to improve the urban water environment,the Yangzhou municipal government issued the "general river chief order"to further promote the policy of river and lake governance,and vigorously carry out river regulation work,including the comprehensive river dredging in the thin west lake scenic area,and the large area of river widening in the Lixia river area,and other river regulation projects have been implemented.Based on the current river network of Yangzhou City,the hydrodynamic mathematical models of one-dimensional and two-dimensional river networks and the one-dimensional water quality mathematical models are establishesed in this paper,and the improvement measures for improving the river overflow capacity in urban areas based on the current river overflow situation are explored.One-dimensional hydrodynamic model and water quality model,are based on the saint venant equations and the one-dimensional water quality equation,in terms of solving methods,the difference equations of each section of the river reach are constructed,and the physical quantity relationship between each section of the river reach and its first and last sections is deduced by using catch-up method.The problem of solving the section is transferred to the problem of solving nodes.Then,the algebraic equations of nodes are constructed on the whole model,and the equations are solved by using iterative method.The hydrodynamic calculation of a typical annular river network is also carried out with this model program,and the results are compared with those in Sen’s paper.Two-dimensional hydrodynamic model is based on the two-dimensional shallow water equation.The derivation process of the transformation from the N-S equation to the two-dimensional shallow water equations are described in this paper.In terms of solution,the control volume method with the best conservation is used to discreteequations,and the Roe scheme is used to obtain the Riemann approximate solution.In addition,the grid property of dry and wet elements is added to make the model suitable for solving the flow calculation problems in discontinuous flow and waterless area,which greatly increases the scope of engineering application and ensures that effective calculation can be carried out even in the dry period.In the numerical simulation of the river network in Yangzhou,considering the regional distribution of the river network and the different inlet and outlet conditions,the east and west regions of the river network were simulated separately for the convenience of model construction and calculation,and the parameters of the model were calibrated by using the measured data.In terms of the selection of hydrodynamic model,the one-dimensional hydrodynamic model with the best comprehensive effect is selected by comparing the calculation results of one-dimensional hydrodynamic model and two-dimensional hydrodynamic model,the engineering efficiency and solution precision are considered.The model is used to calculate the flood discharge modes under different regional water levels and lower tidal levels in the western region,and the optimal river excavation scheme to increase the flow capacity of urban river channels is proposed,which provides theoretical help for improving the flood resistance capacity and water quality optimization construction of the river network in Yangzhou.