%A WANG Pengchao*,YU Jianping %T Numerical simulation of water hammer boundary conditions based on nozzle outflow law %0 Journal Article %D 2020 %J Journal of Drainage and Irrigation Machinery Engin %R 10.3969/j.issn.1674-8530.18.0193 %P 814-818 %V 38 %N 8 %U {http://zzs.ujs.edu.cn/pgjx/CN/abstract/article_2968.shtml} %8 2020-08-25 %X In order to study the water hammer pressure generated at the moment of valve closing, the relationship between the head and flow of the valve cross section was determined by the nozzle outlet flow rule; combined with the characteristic line equation, the water hammer test bench was used as a model, and MATLAB was used to perform water hammer simulation calculations. The results show that the valve end pressure rises rapidly with the valve closing, reaches a maximum value of 0.36 s, and then drops rapidly. With the increase of time, the valve end pressure continuously rises to a peak and then decreases, but its maximum pressur is less than the first peak. By comparing and analyzing with the experimental results of the water hammer test bench, the accuracy of the nozzle outflow model and the calculation program are verified. Therefore, in a simple pressure pipeline, when the end of the pipeline is a valve, the boundary conditions can be established according to the nozzle outlet flow law. On this basis, the valve closing time is taken as 1.0, 2.0, 3.0, 4.0, and 4.8 s in order, and the effect of the valve closing time on the maximum water hammer pressure is simulated. The results show that the valve closing time has a great effect on the water hammer pressure. The longer the valve closing time, the smaller the maximum water hammer pressure. However, as the valve closing time increases, the decrease of the water hammer pressure will become more and more small.