Over constrained Boundary Conditions
 

Can some one please tell me if it is a over constrained approach to specify both volumetric flow rate and pressure on a inlet boundary

yes, absolutely it is over constrained approach. moreover, its not possible to given two boundary conditions at one side.

May i know where you want to use?

Hi,

Can you please tell me how to calculate pressure over the inlet given the volume flow rate and the fluid used being Air

you can calculate velocity for given flow rate. then calculate total pressure over surface by using static pressure plus dynamic pressure.

Still, u had not in circle, describe your problem in detail..