枝状管网水力瞬变工况的试验与数值模拟

采用试验并结合特征线法(MOC)对带有一个分支管管网阀门关闭时产生的水锤压力及波动规律进行了研究,试验采用压力传感器监测水锤压力波动、角位移传感器测定阀门的关闭时间及关闭规律,结果表明:MOC方法能较好地预测管网阀门关闭产生的最大水锤压力值,管网监测点计算与试验值相对误差小于13％,但MOC方法计算所得压力波的衰减比较缓慢,而试验得到的压力波衰减很快,是由于在计算中使用的恒定流摩阻所致;在此基础上对5种阀门关闭方案产生的瞬变流动进行了数值计算,表明管路末端2个阀门同时关闭时管网中产生的水锤压力最大,在实际工程中应避免阀门同时关闭的操作;管网最大水锤压力随关阀时间的延长而减小,当阀门关闭时间一定时,采用曲线关闭规律产生的最大水锤压力比直线关闭规律产生的要小,而采用两阶段直线关闭规律产生的最大水锤压力压力小于线性关闭的,对于实际工况中的两阶段关闭应通过延长第一阶段关闭时间以减小最大水锤压力．

Experiment and numerical simulation of hydraulic transients in branched pipe network

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 two stage straight line closing scheme was lower than that by the one straight line scheme. For the two stage straight line closing scheme, the closing time of the first stage should properly be extended to reduce the maximum water hammer pressure.