A Numerical Study on the Flow Characteristics According to the Operating Speed of Hollow Jet Valve

Abstract

Various types of valves are installed in the emergency discharge facility of dams, and when water is discharged in an emergency, vibration may occur in the valve depending on operating conditions. In this study, for the hollow jet valve, which is frequently used in the emergency discharge facility of dam, the flow phenomenon occurring according to the operating speed of the valve was observed and the vibration characteristics according to the operating speed were investigated through CFD.In particular, when the hollow jet valve is closed, the valve casing is opened while the inside of the valve casing is filled with air, and the open position is also changed during the opening time, thus the calculation was performed using the unsteady 2-phase overset mesh technique.As a result of calculation through CFD, it was found that when the operating speed of the hollow jet valve was changed, the time range of vibration appeared differently, and the value of the drag coefficient generated was also changed. In addition, it was found that the location of vibration generated according to the operating speed is generated at mostly identical locations, the cause of the vibration is not the vibration caused by the hydraulic pressure exiting the hollow jet valve, and it can be seen that the atmosphere outside the valve flows into the valve casing, creating a complex flow phenomenon inside the valve casing and acting as the cause of vibrating the hollow jet valve.