Numerical analysis of bubble collapse with nonequilibrium phase transition by the ghost fluid method

Abstract

The ghost fluid method is improved so as to consider the nonequilibrium phase transition at the vapor-liquid interface during the collapse of bubbles in a compressible liquid. In the present method, the ghost fluids are defined so that the conservation laws at the vapor-liquid interfaces are satisfied; the nonequilibrium condensation and evaporation for the collapse of nonspherical bubbles are taken into account. Also, the idea of adaptive zonal grids is implemented in the ghost fluid method to dissolve the fine structure of the interface of the violent collapsing bubble. The present method is applied to the collapse of a spherical vapor bubble, and the numerical results are compared with the experimental results by Akhatov et al. It is shown that the present method can predict successfully the violent collapse of a spherical bubble even though the Eulerian grid is employed. Also, the present method is applied to simulate the collapse of an axi-symmetric nonspherical vapor bubble induced by the interaction of an incident shock wave with the bubble. The liquid-jet formation and the generation of shock waves from the collapsing nonspherical bubble are also simulated successfully by taking the nonequilibrium condensation and evaporation of vapor into account. When the liquid jet develops on the upstream surface of the bubble, the vapor temperature close to the upstream surface increases due to the latent heat by condensation. After the bubble rebounds, the low temperature region caused by the evaporation is found inside the bubble. © 2012 The Japan Society of Mechanical Engineers.