An improved, Rayleigh-Plesset based homogeneous cavitation model accounting for microbubble behaviour and turbulent interaction
Álvaro Pardo Vigil, L. Fernández, José González, Adrián Pandal
Abstract
A new cavitation model for CFD (Computer Fluid Dynamic) calculations is developed in the present article. The model is designed to reproduce the dynamics of both microbubbles and macroscopic cavities. It is built in the frame of the homogeneous mixture URANS (Unsteady Reynolds-Averaged Navier-Stokes) equations and introduces Rayleigh-Plesset bubble dynamics. The model also accounts for surface tension, viscosity, slip velocity and the presence of noncondensable gases in the fluid. The influence of turbulence is considered based on the pressure drop arising from interactions between microbubbles and turbulent eddies. Such approach implies that, when bubble size rises, the adjacent flow turbulence is also increased resulting on additional cavitation. The new model is firstly calibrated and validated comparing its results for the well-known injector nozzle experiments from Sou et al. (2007). Different cavitating regimes ranging from inception to developed cavitation, including hydraulic flip, are analysed. In all cases, the proposed formulation allows to capture single bubble behaviour as accurately as Lagrangian modeling while maintaining the cost-effectiveness and the suitability for macrocavitation of the Eulerian models. Comparison with the full differential Rayleigh-Plesset equation shows that the presented model is able to describe single bubble behaviour. This represents a significant improvement during the inception stage, in which isolated bubble dynamics are responsible for cavitation.