Influence of the nonequilibrium phase transition on the collapse of inertia nonspherical bubbles in a compressible liquid

In this work, we investigate the shock wave-inertial vapor bubble interactions by taking the nonequilibrium phase transition at the interface, fluid compressibility, and axisymmetric bubble deformations including jet penetration into account. We use the level set method (Sussman et al., 1994) and the ghost fluid method (Fedkiw et al., 1999), which were improved so as to consider the nonequilibrium phase transition (Jinbo & Takahira, 2012). The numerical treatments for heat and mass fluxes through interfaces due to the phase transition are implemented, satisfying the conservation laws of mass, momentum, and energy at the interface and preventing the interface from becoming diffused. The influence of surface tension is also considered in the method. The improved method is applied to the shock-bubble interaction under the experimental conditions by Sankin et al. (2005). The pressure waveform of the incident shock wave is comprised of a leading compressive wave with a peak pressure of 39 MPa and a pulse duration of around 1 μs, followed by a trailing tensile wave of −8 MPa in peak pressure with a pulse duration of around 2 μs which is determined from the experiment. The liquid-jet formation and the generation of shock waves from the collapsing nonspherical bubble are simulated successfully by taking the nonequilibrium phase transition and surface tension into account. The validity of the simulation is shown by comparing the numerical results (e.g. the intensity of the shock wave generated by the bubble collapse and displacement of the bubble centroid) with those obtained from the experiments (Sankin et al., 2005; Klaseboer et al., 2007). We investigate the effects of the phase of bubble oscillations when the incident shock wave impinges on the spherically-shrinking bubble, on the shock wave radiated from the bubble collapse. It is also shown that when the nonequilibrium phase transition at the interface of nonspherically collapsing bubbles is considered, the minimum bubble radius and the maximum space-averaged pressure value inside the bubble reached during its collapse decreases and increases, respectively, compared with those in the case without the phase transition.