The ternary phase field model implemented in COMSOL is based the work of Boyer and co-workers in Ref. 2. The model is designed in order to study the evolution of the three immiscible phases, denoted phase A, phase B, and phase C, respectively. Each phase is represented by a phase field variable
, which takes values between 0 and 1. The phase field variables satisfies the constraint
Here the σij denotes the surface tension coefficient of the interface separating phase
i and
j, and the capillary parameters
Σi are defined as
and Λ is a function or parameter specifying the additional free bulk energy. By default
Λ is zero. In this case it can be seen that the free energy in
Equation 11-30 represents the mixing energy, since only interfaces between two phases (where two phase field variables varies between the limiting values) contributes to the free energy.
In Equation 11-32 ε (SI unit: 1/m) is a parameter controlling the interface thickness,
M0 (SI unit: m
3/s) is a molecular mobility parameter, and the parameter
ΣT is defined as