I am trying to model the pressurization of a volume once a valve is opened. I am running a transient model and for the duration of the simulation there is only the inlet from the valves. I have tried using a pressure boundary which does not seem to be give me the results I want and with the inlet boundary condition it does not seem like the pressures between the two volumes equalize. Any suggestions on setting the correct boundary conditions? Thanks in advance.

I just wanted to clarify this problem. I am using the mass flux option to define my inlet BC. I understand that the density and velocity components are used to find the constant mass flux. The density I am using represents the density of the air at the pressure at the inlet BC. This BC does not seem like it will get me the results I want since the pressure between the two volumes will not equalize but rather continue to increase in the one volume since the mass flux is constant. Any suggestions on setting the correct pressure BC or if this is possible using an inlet BC?