Bulk modulus, ANSYS CFD

[torrot]

I don't understand about when I need to input the bulk modulus in ANSYS CFD. From my current knowledge (which is maybe wrong), it should be needed when compressibility is activated (incom = 1E15, tell me if i'm wrong somewhere). But bulk modulus should be varied by pressure and tempreature. And even thought we were not input it, the bulk modulus should have been able to calculated from gramma(Cp/Cv)*P(pressure) for air.

In brief, I really wannt to know when I need to input bulk modulus in CFD (i'm using ansys).

Thanks in advance