So each material is associated with a phase:
The initial condition is given by this parameter. You can also make subdomains:
And the inlets are being linked to the phase fraction like this (Value 0 = 100% phase 0; Value 1 = 100% phase 1):
.
You should probably also play a little bit with the boundary conditions, especially the pressure outlet, to find out which one is the more appropriate. For this sim I used a plain pressure outlet = 0
Edit: it would be highly appreciated if you update us on your findings when the project is finished (i.e if this modelation proved to be good or not), I’m quite interested in it 