Author(s): Jijian Lian; Xiangpeng Mu; Wuyi Wan
Keywords: Stepped low-pressure water transfer project; Hydraulic oscillation; Resonance; Hydraulic transients; U-shape tube; Incline shaft
Abstract: The stepped low-pressure water transfer project is a new type gravity water transfer system, which is reliable and economical. But as hydraulic transients process takes place, periodic hydraulic oscillation will occur in water transfer units and it may enlarges piecemeal while propagating to the low reaches and come into being severe oscillation at the end of water transfer system, which will make negative effects on the project. According to the hydraulic characteristic of stepped low-pressure water transfer project, the numerical model is established and program is made to simulate unsteady flow for the project. Firstly, the origin cause of water level oscillation in the water transfer system is analyzed. Then through theoretical analysis and derivation, the equation of hydraulic oscillation is proposed and hydraulic natural frequencies are computed, which prove hydraulic resonance exists indeed that results in enlargement of hydraulic oscillation while propagating to lower reaches. Finally the measures to control hydraulic oscillation and avoid hydraulic resonance are suggested in this paper. It is proved that staggering the oscillatory frequency of neighboring water transfer units can avoid hydraulic resonance and decline the enlargement of water level oscillatory while propagating to the low reaches.