Why there are two types of transient studies for laminar two phase flow level set (tpf) module in Comsol (Time dependent and transient with phase initialization) and how to tune the parameters "phi" and "epsilon" for phase initialization? Also, what are the physical meanings of these parameters?

Comsol documentation doesn't bring lot of clarity about how to adjust these parameters and when using the default values of the software.

Same problem for the "phase field" method exists.

If anyone can help and share his experience I will be very greatful.

Thanks

Zahreddine.