Direct numerical simulations of incompressible multiphase magnetohydrodynamics with phase change

A new phase change model has been developed for the simulation of incompressible multiphase magnetohydrodynamics based on the Volume-of-Fluid method. To decrease the pressure oscillations when large density contrasts are present between the liquid phase and the vapor phase, a smooth distribution of sharp mass transfer rate within a narrow region surrounding the interface is adopted, and a ghost-cell approach is used to impose the saturating temperature at the liquid-vapor interface when solving the energy equation. After that, the method has been implemented in an incompressible multiphase magnetohydrodynamics solver developed in our previous work (Zhang and Ni (2014) [3]). Moreover, when computing the electromagnetic fields, a cut-cell approach is implemented to keep the sharpness of the interface, which is treated as an electrically insulating boundary as it translates and deforms with the fluid. The phase change model has been verified for a series of one-dimensional, two-dimensional and three-dimensional problems, while the numerical results agree well with either the theoretical solutions or the experimental data. In particular, by simulating the vapor bubble rising in superheated liquid under nonzero gravity in presence of external magnetic field, the magnetohydrodynamics effect on the vaporization of the rising bubble is investigated and we observe the magnetic fields to suppress the vapor bubble growth during the phase change. At last, both two-dimensional and three-dimensional film boiling simulations are conducted, which show good qualitative agreement with heat transfer correlations, and the vapor bubble is found to elongate along the direction of the magnetic field during its growth, moreover, the time instant for the vapor bubble to detach from the film is also delayed.