[Anna Tian]

Hi,

Ideal gas properties are different from the real gas properties. I noticed that when people simulation airfoil (like the Fluent tutorial), they always choose ideal gas rather than real gas. May I ask why? That won't introduce large error? Why don't they use the real gas?

[agd]

The ideal gas model is a very accurate model over a fairly large range of temperatures and for pressures that are not too high. The definition of "too high" is somewhat fuzzy, but most good thermodynamics books will provide background on when the ideal gas equation of state is not sufficient and should be replaced by a better model, say the van der Waals EOS. One other thing to keep in mind s the difference between an ideal gas model (specific heats are functions of temperature), and the perfect gas model (where the specific heats are constant.)