Numerical Simulation Of Water Hammer In Water Supply Pipeline And Study On Water Hammer Protection Measure

Water supply pipeline is an important part of urban infrastructure, and the runningstatus of it is closely related to the living of urban residents and the production ofindustrial and mining enterprise. However, there are many factors such as stopping ofpumps in emergency and misoperation of valve can cause a sudden change of velocityin water supply system and so on, and the sudden change can result in a destructivewater hammer., therefore, the use of the appropriate measures and the theoreticalanalysis and research on preventative control of water hammer is an importantprerequisite for optimizing the engineering design and the safe operation of watersupply pipeline, which has great theoretical significance and practical valve.Based on the HAMMER water hammer analysis software, this paper is focused onnumerical simulation on water hammer and study on water hammer protective measuresin water supply pipeline. Firstly, the water hammer basic theory and method ofcalculation is introduced, and the modeling capabilities, modeling principles, modelingdate and modeling steps of the HAMMER software is described and the numericalsimulation results are verified by hydraulic pilot experiments by the HAMMER waterhammer analysis software. Secondly, the impact factors of valve-closed water hammerin simple pipeline is also analyzed on the basis of the simulation programs which isdesigned according to the response surface methodology, and the impact ratingdescription of water hammer risk is evaluation based on risk matrix. Lastly, taking waterhammer protection of a high lift water supply pipeline for example, the features of waterhammer protection and the influence factors for protection efficiency are analyzed suchas air valve, slow butterfly valve, rotational inertia of pump, one-way surge tank,bidirectional surge tank, air vessel, two-level check valves, nodes outflow along thepipeline, and the application scope of protective measures is put forward. Taking waterhammer protection of a long distance and large flow water delivery pipeline forexample, the solution for such project’ water hammer protection is proposed. Taking aregional water supply network for example, the features of water hammer conditions aresimulated such as stopping of pumps in emergency, pump speed changes, closing valvequickly, node flow changes, and the water hammer protection measures arerecommended for local pipeline in water supply network. The main conclusions arepresented as follows: ①The numerical simulation results are basically identified with the pilotexperimental results. The mathematical model and solution algorithm for the practicalengineering and the more accurate results can be obtained.②The greater the flow, the higher the lift, the bigger the wave velocity, the longerthe pipeline and the shorter the duration of closing-valve, the maximum water hammerpressure before the valve will be greater, and the impact of various factors on themaximum is significant. Water hammer risk level of a high lift water supply pipelineand a long distance and large flow water delivery pipeline is high risk; therefore, thewater hammer protection measures should be taken to reduce the risk.③Air vessel is better to be used under the circumstances of small flow and highlift., and the best place to set an air vessel is near the check valve before the pump outlet.The air vessel has a better water hammer protection effect when the parameters,including the connecting pipe diameter, the initial pressure, air initial volume, is setreasonably. However, the solution of the slow butterfly valve and air valve plays alimited role in eliminating the negative pressure in a steep slope and high lift system aswell as the one-way surge tank solution. It is favorable for water hammer protection touse the larger rotational inertia of pump, and it can be used as a supplementary measure.One-way surge tank and bidirectional surge tank should be separately set near the nodewhere is more likely to occur water hammer of cavities collapsing and the pump outlet,and the bidirectional surge tank is not suitable to use in the high lift water supplypipeline on account of its set height and causing easily the secondary pollution problemof water quality and other problem. If there is a node outflow along the water supplypipeline, and giving priority to the node that is more likely to occur water hammer ofcavities collapsing, so as to weaken the water hammer pressure. The two-level checksolution can reduce the water hammer pressure of the check valve near the pump andprotect the pipeline near the pump station, when it is in conjunction with air valve orsurge tank, its water hammer pressure is reduced, but the protective effect of negativepressure is limited.④By means of setting reasonably air valve and relief valve,the positive andnegative pressure water hammer, resulting from misoperation of valve, can beeffectively eliminated in a large flow and long distance water delivery pipeline, and theprotection requirements of valve closing water hammer under the different flow can bemet, and its solution can be provided as reference for the same type of water hammerprotection project. ⑤The impact of pump-stopping water hammer on pressure is relate to waterconsumption in a water supply network. The changing speed has an effect on nodepressure fluctuations when variable pumps are adopted in a water supply network; theimpact of quick-closing valve on pressure change is relate to the position of valve in awater supply network; the pressure of other nodes can be affected when the flow of anode increase suddenly, and the impact depend on the distance of nodes; the stopping ofpumps in emergency has an effect on the entire water supply network, and it should betaken into account the most unfavorable condition of water hammer protection, besides,air valve, relief valve and the other water hammer protective measures can beconsidered to adopt to protect the water hammer of local pipeline.