Hello Hiba, 

You can model air using Abaqus/CFD or using CEL technique in Abaqus/Explicit. 

Could you please elaborate more about your model. I mean is it kind of fluid structure interaction problem? 

Regards,

Ranjith.

Hi Ranjith,

  thanks for your replay, in fact I am trying to simulate an Air layer above a section  of pavement, and I need to know the velocity of the receiving signal by a sensors located on the air media, the out put will be as apressure but I need a velocity ...how could I get V2 for acoustic media instead of POR out put ?? 

Thanks