Numerical Simulation Of Three Dimensional Water Hammer In A Pressure Pipe System

Pressure pipe system is an important part of water conveyance system.The phenomenon of water hammer is often accompanied by high pressure pipeline in the process of hydroelectric generation,and this phenomenon is inevitable.In order to reduce the impact of water hammer on the pressure pipeline system in a hydropower station,the pressure regulating chamber is usually arranged in a pressure pipe system to destroy the sealing of the pressure pipe system.The joint operation of water hammer and pressure regulating chamber affects the safety of the hydropower station,which has always been the most concerned problem in the research of hydropower stations.The three-dimensional numerical simulation of unsteady flow in pressurized pipeline system can provide theoretical reference for similar projects,and provide a research direction for numerical simulation of pressure pipe system.In this thesis,SOLIDWORKS was to establish a three-dimensional model,GAMBIT model was used to do partition structured grid,and FLUENT was used to calculate the unsteady flow.Finally,the results were processed by TECPLOT.The model mainly included a concrete tunnel,a surge tank and two high-pressure pipeline.Dynamic mesh technology was used to realize the dynamic opening and closing of valves.Since the surge tank involved the continuous exchange of two media of air and water,the mature VOF technology was used to deal with this technical problem.In this thesis,a three-dimensional unsteady flow numerical model of a pressure pipeline system was verified by using the existing model test results of the physical model of the Liujiaxia pressure pipeline.The results showed that this study could be an effective way to study three dimensional pressure pipe system with a surge tank.Under the condition of the decreasing load,the results showed that: The clockwise vortex appeared at the junction between the generating branch and the surge shaft.There was a clockwise vortex near the high pressure pipe near the valve.The flow pattern of high pressure pipes varied greatly at elbow.During the propagation period of a water hammer wave,the velocity of the pressure pipe system first decreased,and then increased.The maximum flow rate occurred in a surge tank.During the propagation period of a water hammer wave,the pressure in the generating branch hole,the surge shaft and the high pressure pipe first increased,and then decreases.The maximum pressure occurred in the area near the valve which was near the high pressure pipe.During the propagation period of a water hammer wave,the turbulent energy dissipation rate and the turbulent dissipation rate decreased gradually.And they gradually moved to the bottom of the well.The surge shaft had the largest turbulence in the elbow area near the valve.Under the condition of the increasing load,the results showed that: There was a clockwise whirlpool at the junction between the generating branch and the surge shaft.There was a clockwise vortex near the high pressure pipe which was near the valve.During the propagation period of a water hammer wave,the velocity of the pressure piping system first increased and then decreases.The maximum flow rate occurred in a surge tank.During the propagation period of a water hammer wave,the pressure of the power generation hole,first decreased and then increased.It appeared negative pressure in the 1/4 cycle.The maximum pressure occurred in the area near the valve which was near the high-pressure pipeline.During the propagation period of a water hammer wave,the turbulent energy dissipation rate and the turbulent dissipation rate decreased gradually.And they gradually moved to the bottom of the well.The surge shaft had the largest turbulence in the elbow area near the valve.