Spectral analysis of gaseous cavitation in water through multiphase mathematical and acoustic methods

Abstract

Mathematical modeling is applied as an effective tool for prediction of cavitation in hydraulic components and systems. A multiphase mathematical model based on the change in phase between water and vapor is typically used to investigate the cavitation flow. However, dissolved air can significantly affect the cavitation. This study proposes a new approach based on a multiphase turbulent mathematical model by adding the air into the mixture to solve the dynamics of cavitation. To clearly assess the significance of air in the multiphase model, four variants of the mixture are investigated (water; water and vapor; water and air; and water, vapor, and air together). The software of the computational fluid dynamics ANSYS Fluent was applied to numerically solve the proposed mathematical models. The influence of gaseous components is analyzed through evaluation of hydraulic parameters and spectral characteristics of the cavitation bubble. To verify the proposed mathematical models, a hydraulic water circuit was built to generate cavitation in a transparent Venturi nozzle. Cavitation in the experiment was identified by measuring the flow rate, static pressure, and noise and visualized with a camera. The numerical results of the extended multiphase flow confirmed very good agreement with experimentally obtained basic hydraulic parameters and frequency-related characteristics. Knowledge obtained from the multiphase mathematical model of cavitation can be applied to cavitation in the oil flow (pump suction and flow through the valve) in future research, where the effect of the air on cavitation is more important than the effect of vapor.