Lift force coefficient for 2-phase flow
 

Hello, I am using Eulerian multiphase model to simulate air-water two-phase flow. I would like to define the lift force coefficient using UDF. Since the lift force on the air is equal to the negative value of lift force on the liquid, I want to know which lift force coefficient I should define in my UDF, the one on the primary phase (air) or the secondary phase (liquid). Any suggestion is valuable and welcome. Thank you very much!