Numerical Method to Provide Cavitation Index for Control Valves

Cavitation is a harmful phenomenon for control valves. Starting from noise and vibration, cavitation can bring erosion and pitting of mechanical parts. Experimental costs for cavitation tests are high, not even considering the difficulties to test large-sized valves. For those reasons a CFD analysis could be an attractive solution to predict cavitation. However, a reliable numerical prediction of cavitation inception is hard to achieve and the computational cost of complex multi-phase models, necessary for a correct description of this phenomenon, is often very high. The purpose of this research is to overcome those difficulties by using a single-phase model to predict the onset of cavitation, in terms of the incipient cavitation index introduced in several technical standards. A method, based on the generalized pressure criterion reported in previous works, is applied to particularly complex control devices, namely the Cage Ball control valves, in which perforated plates are inserted to increase the energy dissipation with respect to a traditional Ball valve. Numerical results are compared with our own experimental data of acceleration induced by cavitation vibrations, showing good agreement. The final result is a simple and reliable method, with low computational cost, to evaluate the incipient cavitation index for control valves.