Numerical Simulation Method For Large Scale River Networks Hydraulics And Water Quality

Numerical Simulation Method for Large Scale River Networks Hydraulics and Water QualityABSTRACTBased on the Saint-venant equations describing the channel flow movement, the nonlinear algebraic equations derived by the use of Preissmann weighted implicit four-point scheme are solved with the Netwon-Raphson method. A combined Gauss main-element elimination method with compress-storage technique is proposed. The relaxation iterative method for solving branch river networks is extended, which can turn the problem of any complex river networks into the problem of a series of single rivers. The coupling of hydraulic model with water quality model is built up. The combined model was applied to a large complicated river networks with numerical hydraulic structure which influenced by strong tide, storm and heave rain. Visualization of computational results is realized by means of Maplnfo, which displays the computational results in fast, convenient and accurate way. The main achievements are as follows:1. Based on the Saint-venant equations describing the channel flow movement, the nonlinear algebraic equations derived by the use of Preissmann weighted implicit four-point scheme are solved with the Netwon-Raphson method, which raises the accurate of the numerical solution, and the convergence of the numerical solution is discussed,2. A combined Gauss main-element elimination method with compress-storage technique is proposed, which with the characteristic of less -storage requirement, small rounding off and high stability, and solved the problem of large storage requirements in solving large linear algebraic equations in river networks hydraulics,3. The relaxation iterative method of branch flow in tree-type river systems is extended to the loop-type river networks, which can turn the problem of any complex river networks hydraulics into the problem of a series of single river hydraulics;4. Considering the different definition of the junction and channel between the model of hydraulics and water quality, the automatic Unking the model of hydraulics with water quality in any complex river networks is built up, with which based on the flow pattern from computation, the problem of water quality numerical simulation in large scale complex river networks can be solved;5. According to the needs of the actual problems in hydraulics and water quality, analysis the relation of the junctions, channels between the hydraulics model and water quality model and the relation of the entire river networks and the local river networks, by this way adding junctions, adding or reducing rivers to the water networks and computation to entire river networks and the local river networks can be realized,6. Based on geographic information system software Maplnfo, and integration the software of Visual Basic, Brand C++ and so on, Visualization of the results of computation as water lever and flow is realized, which benefits for the management to manage in fast, convenient and accurate way.