i'm using FLUENT 5 to model multiphase separator, when i display the volume fraction contour of the separator, it does not show separate interface between the phases or the whole volume in separator is filled with the phases disorderly, can anyone tell me why? by the way, i only set the boundry condition at the inlet and outlet, do i need to make additional setting?

What kind of separator are you trying to modeling.

If it is something like a settling take you will need to activate gravity.

Alain