Research On Several Problems Of 1D Unsteady Channel Flow

In recent decades, the tidal bore and frequent flood bring serious calamity to people's life and property, hinder nation's persistent development. Thesis on the basis of summarizing forefathers and studying the tide, set up one-dimensional tide numerical model. Through simulating bore, the two conditions for tidal bore have been studied. And it has analyzed the roughness rate relation to the tidal bore and drawn some meaningful achievements. As to non-linear hydrology system, one-dimensional hydraulic model for hydrologic forecast has problem on precision, thesis has proposed a real-time forecasting method based on hydraulic model, raising the precision of prediction of the model, and applied the model to the research of the practical problem.Chapter 1 has given the object and aim of study in the paper, summarized the current research situation of tidal bore and flood routing. And the main methods of simulation been and the numerical methods in common use to describe flow movement s have been introduced detailed in the paper.Chapter 2 has set up one-dimensional numerical model to serve for the simulation of tidal bore, which is based on the finite volume method and up-wind scheme. According to some similar characteristics of tidal bore, water jump and dam break, it has been analyzed the precision of one-dimensional model with water-jump calculation and the exact resolving of instantaneously breaking bam. The result showed that the established model is more rational to simulate tide bore.Chapter 3 has analyzed the origin cause of tidal bore through simulating bore with one-dimensional bore model based on the ideal rectangle cross watercourse. The result of calculation indicated that the deformation of tidal wave has close relation to the river topography include length, riverbed of river trace to the source lifting and shrinking river width, these factors have offered the condition for deformation of the tide wave. The tide range is the motive power for tidal wave tracing back in the course. The law that roughness affects alteration of tidal bore was obtained.Chapter 4 has developed a real-time forecasting method coupling hydraulic model of 1D unsteady flow with recursive least squares. The ID unsteady flow model is modified by using the time-variant parameter and revising it dynamically through introducing avariable weighted forgetting factor, that the output of the model can be adjusted for real time forecasting of floods. And applying in the reach from Yichang to Luoshan of the Yangtze River. Based on the relief map of river in 1993, the manning coefficient is calculated, and the flood of 1996 and 1998 has been repeated. Computational result shows that the forecasting accuracy of the new model is much higher than that of the original hydraulics model of ID unsteady flow. The method developed is effective for flood forecasting, and its reliability has been tested.Chapter 5 has sum up the whole paper and prospect further research work.