i'm trying to simulate a two-phase flow (water(99%) +air(1%)) inside a centrifugal pump. I'm using CFX.
I set up air as a dispersed fluid(mean diamter 0.5mm) and water as the continuous one. My inlet condition is the BulkMassFlow and the values of the volume fraction (air=0.01 and water=0.99). At the outlet i set the static pressure.
When the simulation is over in post-processing it looks like that CFX "loosing" the air fraction directly after the inlet. Therefore I have only a two phase flow at the inlet and in the rest of the pump the air is vanished. (See the attatched picture)
CFX set the default value for minimum volume fraction of 1.0E-15.
But if i choose in CFX-Pre to set up a value for the minimum volume fraction the simulation diverged and i get a "fatal overflow" error...
Does somebody know how i can fix it? I would be very grateful!