The purpose of this study is to examine multi-physics computational fluid dynamics method, NS-PFM, which is a combination of Navier-Stokes (NS) equations with phase-field model (PFM) based on the free-energy theory, for interface-capturing/tracking simulation of two-phase flows. First, a new NS-PFM which we have proposed was applied to immiscible, incompressible, isothermal two-phase flow problems with a high density ratio equivalent to that of an air-water system. In this method, a Cahn-Hilliard equation was used for prediction of diffusive interface configuration. The numerical simulations demonstrated that (1) predicted collapse of two-dimensional liquid column in a gas under gravity agreed well with available data at aspect ratios of column = 1 and 2, and (2) coalescence of free-fall drops into a liquid film was successfully simulated in three dimensions. Second, we took heat transfer into account in another NS-PFM which solves a full set of NS equations and the van-der-Waals equation of state. Through a numerical simulation of a non-ideal fluid flow in the vicinity of the critical point, it was confirmed that the NS-PFM is applicable to thermal liquid-vapor flow problems with phase change.

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