Experiment and numerical simulation of hydraulic transients in branched pipe network
(1. College of Water Resources and Architectural Engineering, Northwest A＆F University, Yangling, Shaanxi 712100, China; 2. Institute of Watersaving Agriculture in Arid Areas of China(IWSA), Northwest A＆F University, Yangling, Shaanxi 712100, China)
Abstract：The water hammer pressure and fluctuation in a branched pipe network were studied by experiment and the method of characteristics (MOC) when the valve is closed. In experiment a pressure sensor was used to monitor water hammer pressure and fluctuation and the angular displacement sensor was adopted to measure the closing time and opening of the valve. The results showed that the MOC can better predict the maximum water hammer pressure caused by valve closing in the network with a relative error of less than 13%. The pressure wave attenuation in simulation is slower than in experiment because the friction factor of steady flow is used in the simulation. Based on that analysis, the transient flows generated by other five closing schemes of valve have been simulated numerically. It was shown that the maximum water hammer pressure was generated in the network when the two valves at the network end were closed simultaneously; suggesting this case should be avoided in applications. The maximum water hammer pressure was reduced with increasing closing time. For a constant closing time, the maximum water hammer pressure generated by a curved line closing scheme or a twostage straight line closing scheme was lower than that by the one straight line scheme. For the twostage straight line closing scheme, the closing time of the first stage should properly be extended to reduce the maximum water hammer pressure.
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