[Joe Wang]

Hi, Foamers,
I would like to integrate the air mass in a certain domain solved with compressibleInterFoam. Since air phase is compressible, an approximate way I would use is let
rho_air = rho - alpha.water * rho_water
where I assume rho_water is a constant when alpha.water equals to 1.
However, when I checked the calculation results, it's not true. rho_water changes along with pressure changing. I thought compressibleInterFoam only takes gas as the compressible phase. Am I wrong?
And regardless of I'm correct or wrong, does someone know how to calculate the gas mass in a certain domain in a multi-phase flow field?
Hope someone knows more about the hypothesis of this solver and clear up my confusion. Thanks.

Joe