  The phase-field method is used as a basis to develop a strictly mass
conserving, yet simple, model for simulation of two-phase flow. The model is
aimed to be applied for the study of structure evolution in metallic foams. In
this regard, the critical issue is to control the rate of bubble coalescence
compared to concurrent processes such as their rearrangement due to fluid
motion. In the present model, this is achieved by tuning the interface energy
as a free parameter. The model is validated by a number of benchmark tests.
First, stability of a two dimensional bubble is investigated by the
Young-Laplace law for different values of the interface energy. Then, the
coalescence of two bubbles is simulated until the system reaches equilibrium
with a circular shape. To address the major capability of the present model for
the formation of foam structure, the bubble coalescence is simulated for
various values of interface energy in order to slow down the merging process.
These simulations are repeated in the presence of a rotational flow to
highlight the fact that the model allows to suppress the coalescence process
compared to the motion of bubbles relative to each other.
