[lzhaok6]

Dear all,

In FLUENT, VOF two-phase flow allows one phase to be compressible gas as says in the theory guide "Only one of the phases can be defined as a compressible ideal gas. There is no limitation on using compressible liquids using user-defined functions.".

However, also based on the theory guide, governing equations are shared among the phases, which means only one set of NS equation is solved. Let's suppose a two-phase flow with compressible ideal gas and incompressible fluid. Compressible gas needs ideal gas law to close the NS equation whereas incompressible fluid doesn't. Also, density is dropped in incompressible fluid continuity equation. How could FLUENT use only one set of NS equation to solve both phases??

I suppose the correct way to model compressible gas and incompressible fluid two-phase flow is to let each phase use its own governing equations and couple the phases by Ghost Fluid Method and track the interface using Level-set method.