Pressure difference through Vortex
 

Hey guys, im looking for a little help running FLUENT more accuratly.
my model is a vortex diode that has a tangential port and an axial port with water flowing through it. I am running the RSM turbulence model with the default constants. I have a mass flow Inlet and an outlet vent. im an interested in finding the differences of pressure from the inlet to the outlet.
any advice would be helpful. What equations can i use to calculate the constants for RSM? should i use K-epsilon instead? LES? would a different inlet or oulet be better? any kind of information is helpful.