Compressible / weakly compressible flow

[Amine A]

Hello , can anyone please tell me what is the difference between compressible and weakly compressible flow in term of equations ?
Both have ∂ρ/∂t + ρ∇u = 0

 

[1503-44]

Weakly compressible flow is mostly applied to liquids, but it can also be used for low pressure gases. When weakly compressible applies to gases, it means that they can be modeled using the ideal gas eqauations, whereas a compressibility factor must be introduced whenever those linear relationships break down, usually at higher pressures or over wide temperature ranges.

https://en.m.wikipedia.org/wiki/Ideal_gas_law

https://en.m.wikipedia.org/wiki/Compressibility_factor

 

[Amine A]

is the air ,for cfd simulation, should be meshed or not ?