Investigation of Hydraulic Conditions and Shape of Flip Bucket Spillways on Cavitation Phenomenon by Considering Dynamic Pressures

Abstract

Cavitation is one of the destructive phenomena which occurs in hydraulic structures and can cause considerable damage to them. This phenomenon is likely to take place in parts of hydraulic structures where the flow velocity is high and water pressure is below the water vapor pressure, thereby leading to the formation of cavitation bubbles. Dynamic pressures may, frequently and in short time periods, reduce flow pressure to below the vapor pressure of water and form cavitation bubbles as a result. Taking dynamic pressures into account, this study examines the potential for the occurrence of cavitation in flip bucket spillways. This research is based on experimental studies and it focuses on the cavitation phenomenon by measurements of pressure fluctuations along flip bucket spillways with different geometrical characteristics. Measurements of dynamic and statics pressures on three different models of flip buckets were made within a range of different Froude numbers. Using statistical analyses on pressure fluctuations, this study has obtained the equivalent pressures of the 0.1% incidence probability, which, in turn, have been used, along with static pressures, for calculating the cavitation. Results show that as the Froude number increases (from nearly five to almost ten), the cavitation index decreases, and after that, the trend of cavitation index is reversed and starts to rise. Also, it is demonstrated that the cavitation probability on inlet and outlet scope of the flip bucket is higher than the middle part. Hence, cavitation incidence probability increases while the ratio of width to radius of the bucket rises.