Study On Hydraulic Transient Flow Analysis And Predictive Control Of Multiple Water Hammer Of Cavities Collapsing

Incidence often happens while pipeline is working such as pump accidently stopping,and workers operating improperly,which causes the acceleration of velocity in the pipe eventually varies the pressure.This phenomenon is called water hammer.Among them,the most destructive force is produced by the water hammer of cavities collapsing,and the pressure produced by the water hammer of cavities collapsing can reach more than ten times of the common water hammer pressure,which is the main cause of the pipeline explosion accident.Water hammer phenomenon occurs in a short time,which not easy to capture the phenomenon,and the destructive force of water hammer of cavities collapsing is very strong,so it is difficult to carry out theoretical experiments through practical engineering,mainly based on the experimental model to study.In the past,most of the scholars have tried to achieve a single water hammer of cavities collapsing as the research model,which is different from the simultaneous occurrence multiple water hammer of cavities collapsing.Due to the multiple cavities collapsing to produce the reflection and superposition of the water hammer wave,the pressure rise and the length of the cavity are all beyond the single cavities collapsing.Currently,there are still some deficiencies in understanding of the characteristics of the multiple cavities collapsing water hammer and the accuracy of the simulation model,which requires to be further studied.This research on the predictive control of transient is the key to optimize the engineering design,reduce the project cost and ensure the safe operation of the project,which has important practical value.In this paper,the water hammer test platform was established to achieve multiple cavities collapsing water hammer.Experiment were observed and the theoretical analysis of the transient flow pattern was carried out.By using the different flow velocity and the closing speed of the valve,multiple test schemes were set up,and summarized the influencing factors of the pressure rise and cavity length.Through the high-speed camera to observe the shape of the cavity and the water surface curve in the process of collapsing the cavity,provides a reference for the simulation of water hammer model.In this paper,based on the existing theories,further study was carried out to establish the simulation program for the calculation of water hammer with multiple cavities collapsing.A new language C++ was adopted,which was referred as C program.The new program was applied the five times to fit the pump characteristic curve five times,improving the calculation formula of water hammer wave velocity,considering the change of friction in hydraulic transient process.The pipe section was a cavity model unit in the new program.The model described the change of water surface curve in the process of simulating the cavities collapsing,which was very similar to the actual situation.The number of threads in the program was optimized,and the running speed of the calculation model was improved.The simulated values of the new program were compared with the measured data in the laboratory,and the error of the new program simulation test was within the acceptable range.Finally,by comparing and analyzing the simulation results of the laboratory conditions and the actual engineering projects with several foreign software,it can be seen that the new program has the advantages inaccuracy and calculation speed,which is worthy of popularization and application.