Rob
Ansys Employee

Sketch out your geometry and include your boundary condition & solids location (if patched rather than flowing into the domain).  Write out what reacts with what, and in which phase.  While you're doing that, think about what you're actually trying to achieve: the above looks like a list of models but I don't actually know what you want to do. 


Finally, have a look at the P1 model limitations: why did you choose to use that one?


I'll also move this to the CFD area as it's not multiphysics.