| Sharp increase in water consumption and water distribution’s unevenness in time and space have exacerbated the confliction between water supply and water demand. Develop water-supply projects with large scale, long distance and cross-basin which work efficiently in solving regional variations in water distribution and easing the contradiction between supply and demand have been an emergency. Yellow River diversion project in the middle of Shanxi Province is one of significant projects in water network construction of 12 th "five-year plan", with long distance, variable diversions, complicated flow conditions and safety problems stand out in operation. Basing on the project, the study has exploited a numerical simulation and calculation software and analysis of the pipe-channel system transition process. The main content of this paper is as follow:(1) Basing on the hypothesis of one-dimensional unsteady flow in open channel and pipeline unsteady flow and the variable time step method, a mathematical model for simulating calculation between pressure pipeline and open channel was developed.(2) Improve the mathematical model of hydraulic transient simulation in complex system. Under the hypothesis of pipe and open channel mathematical model for calculating friction as well as time step were improved to increase numerical simulation accuracy.(3) Different boundary conditions as well as the numerical equations were proposed, including the joint between open channel and the inverted siphon, approximate calculation methods of horseshoe cross section, the joints of pressure tunnel with different cross section forms, the calculation model of gate and bleeder, etc.(4) A numerical simulation system of hydraulic transient in complex water supply system was developed with Visual Basic 6.0, which has full functions, simple operations, reliable performances and friendly user interfaces.(5) The research simulated hydraulic transient of Shanxi Yellow River diversion project to determine the safety operation mode of this water supply system and analyzed the gate control laws.Conclusions of the research:(1)MIAB friction model is more suitable for transient friction calculation than "quasi-stable state" calculation model and adjustment of wave velocity method to calculate time step is more down-to-earth.(2) Under the hypothesis of pipe and open channel mathematical model, a numerical simulation system of hydraulic transient in complex water supply system with applying of Visual Basic 6.0 and SQL 2000 database was developed, with results conform to the general law of hydraulics, high reliability and can be used as hydraulic scheduling basis for the related technical personnel.(3) Use the numerical simulation system to simulate the transient process of Shanxi Yellow River diversion project, the results as follows: ①Universal laws of gate control were found, that gate opening rate has no effect on the state of steady flow, but the greater the gate opening rate, the greater the water level range in the transient process; ②Determine the gate safe operation model of this engineering; ③ Open channel and pipe can satisfy the requirement of safe operation on design condition with reasonable operation mode had verified the rationality of engineering design. |
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