Cavitation is changed phenomena vapor phase from liquid in fluid flow. Phase can change caused pressure drop or temperatur increased. Pressure drop occurred because acceleration flow caused reduction flow area. Cavitation can be occurred on pump suction, pump impeller and valve in piping system. Cavitation indication by raised vapor bubble, noise, and vibration on pipe.
            Numerical study is used to identify cavitation process on gate valve using Fluent 6.2 software. Flow simulation under steady, unsteady and cavitation condition. The fluid is water with variation valve-open ratio, velocity inlet and temperatur. Cavitation is analized from result visualisation whose pressure contour, vapor volume fraction and velocity vector.
            This study resulting cavitation happen for valve-open ratio D/Do=0.29 and D/Do=0.42 with temperature 80°C and 90°C. Increasing fluid temperatur not much effect in pressure drop, but it  increase the vaporation pressure. Pressure drop and increased temperatur cause the flow near cavitation condition. Cavitation on gate valve is occurred in vena contracta and downstream flow because separated flow.

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