  This study presents a novel pressure-based methodology for the efficient
numerical solution of a four-equation two-phase diffuse interface model. The
proposed methodology has the potential to simulate low-Mach flows with mass
transfer. In contrast to the classical conservative four-equation model
formulation, the adopted set of equations features volume fraction,
temperature, velocity and pressure as the primary variables. The model includes
the effects of viscosity, surface tension, thermal conductivity and gravity,
and has the ability to incorporate complex equations of state. Additionally, a
Gibbs free energy relaxation procedure is used to model mass transfer. A key
characteristic of the proposed methodology is the use of high performance and
scalable solvers for the solution of the Helmholtz equation for the pressure,
which drastically reduces the computational cost compared to analogous
density-based approaches. We demonstrate the capabilities of the methodology to
simulate flows with large density and viscosity ratios through extended
verification against a range of different test cases. Finally, the potential of
the methodology to tackle challenging phase change flows is demonstrated with
the simulation of three-dimensional nucleate boiling.
