The Ternary Phase Field Interface
The Ternary Phase Field (terpf) interface (), found under the Mathematics>Moving Interface branch () when adding a physics interface, is used to track moving interfaces separating three different phases. The interface solves four transport equations: two equations governing phase field variables, ϕA and ϕB, and two equations for the corresponding generalized chemical potentials, ηA and ηB. The position of the interfaces are determined by minimization of the free energy.
The phase field variables are defined such that they represent the volume fraction of the respective phase. The volume fraction of the third phase not solved for, but computed from the natural constraint that the sum of the volume fractions of all phases is one.
The main node of the interface is the Phase Field Model feature, which adds the phase field equations and provides an interface for defining the phase field model properties such as surface tensions and parameters controlling the interface thickness.
When this physics interface is added, the following default nodes are also added in the Model BuilderMixture Properties, Wetted Wall and Initial Values. Then, from the Physics toolbar, add other nodes that implement, for example, boundary conditions. You can also right-click Ternary Phase Field to select physics features from the context menu.
Settings
The Label is the default physics interface name.
The Name is used primarily as a scope prefix for variables defined by the physics interface. Refer to such physics interface variables in expressions using the pattern <name>.<variable_name>. In order to distinguish between variables belonging to different physics interfaces, the name string must be unique. Only letters, numbers, and underscores (_) are permitted in the Name field. The first character must be a letter.
The default Name (for the first physics interface in the model) is terpf.
Dependent Variables
This interface defines the dependent variables (fields):
Phase field variable, fluid A phiA
Phase field variable, fluid B phiB
Generalized chemical potential of fluid A etaA
Generalized chemical potential of fluid B etaB
If required, edit the any of the names, but dependent variables must be unique within a model.