hello,

i'm trying to simulate a natural convection problem and I have 2 options for air, ideal gas and incompressible ideal-gas, what's the difference among them? Thanks.

Hi! I'm not an expert, but I am also working with natural convection. I asked myself the same question as you, and I finally found this:

The efects of compressibility are important if you have big pressure differences or high velocity. When Mach number is small (less than 0.1) compressibility efects are negligible and the variation of gas density with pressure can safely be ignored in your flow modeling. So, in natural convection, incompressible ideal gas is normally a good election.