Stratified flow modelling
 

Hello dear users
I want to model water and air flow through a pipe in which the flow pattern is stratified flow. I need to find a gross amount of pressure drop of fluids.
I used eulerian-eulerian inhomogeneous model for the solution. The problem is that CFX needs a drag coefficient to start simulation. CFX default value is 0.44 for drag coefficient. I will appriciate your help on this drag coe. and exactly where i can find a trustable reference for this value...
Thanks in advance...