Study On The Hydrodynamic And Water Quality Model In River

The worsen environment of lake, river and estuary is one of the serious questions in our country. In treating the water pollution, we must hold how the pollutants mix, transfer and distribute along with the water flow in order to find the treatment method quickly. Based on the research work of former summarized and the need of the research task, the systemic review is made of one-dimensional river networks, two and three dimensional curvilinear coordinate transformation, turbulent model, free surface and water quality model. The research emphasis of this thesis is to study the hydrodynamic and water quality model of one dimension, two-dimension, three-dimension. Based on the Saint-Venant equations, the hydrodynamic and water quality model of one-dimension is set up. In calculating two-dimensional and three-dimensional models, the curvilinear coordinate system is used to treat the irregular boundary and improve the computed precision. At the same time, it can reduce the computed time and storage of computer. The staggered grid of B type is adopted to lay the variables. The hydrodynamic and water quality models are validated to simulate the river netwoks, the curved channel of laboratory, natural-river.These models are built in this thesis, the hydrodynamic and water quality model of one-dimension, the planar 2D k-εturbulent hydrodynamic and water quality model of river, the 3D k-εturbulent hydrodynamic and water quality model of river. The transform formula is deduced of Reynolds Averaged Navier Stokes(RANS) equation in planar 2Dξ-ηcoordinates, and fully 3Dξ-η-ζcoordinates at the same time. Based on the theory of WASP water quality model, the water quality model concludes twelve variables: PHYT, NH3, NO3, OPO4, CBOD, COD, DO, ON, OP, conductivity, pH and temperature and considers the variables transformation and affect each other.Base on the Saint-Venant equations and the advection-dispersion equations of one dimension, the Preissmann implicit scheme and the implicit finite scheme are used to discrete the Saint-Venant equations and the water quality equation. The river-junction-river method is applied to resolve the hydrodynamic and water quality model for river networks. The one-dimensional model of hydrodynamic and water quality is applied to simulate flood routing of single-river, unsteady flow of tree-type, looped open channel networks and river networks. The results of levels, flows and discharge distribution between the branches are presented. The water quality is validated corresponsively and time course of contamination variables are given in this thesis. The simulated trends and magnitudes of water quality constituents were generally in good agreement with field observations. The calculated results show that this model can be used to simulate the concentration of water quality constituents in river networks with the flood tide and ebb tide, not only single-river and tree-type river networks but also complex looped river networks.The two-dimensional model of hydrodynamic and water quality is set up in curvilinear coordinate, the control volume method is used to disperse the equations and the flow calculation adopts the SIMPLEC algorithm to acquire the coupling of velocity and pressure. The curved channel in laboratory is selected to validate the depth-averaged 2D model. The velocity and water level at all sections are presented and are compared with the data of experiment. This results show that this hydrodynamic model is credible. This model is applied to simulate the reservoir of Post Fall and these results validate the reliability of this model.The 3D model of hydrodynamic and water quality is set up in curvilinear coordinate, the water level of this model is determined from 2D Poisson equation derived from 2D depth averaged momentum equations. The k-εturbulent mathematic model is used to calculate the reynold stress. The fully coordinate transformation is used to represent the free surface and bed topography. The control volume method is used to disperse the equations and the flow calculation adopts the SIMPLEC algorithm to acquire the coupling of velocity and pressure. This model is applied to simulate the channel bend in the laboratory, the part section of Fall river and the flows in the meander channel with straight flood plain banks, the results are given and validated with measurements. The model is applied to calculate the flow and water quality of the FuLing river and then the pollutant diffuseness of bank discharge is forecast in WanZhou river and ChongQing river.