Back Pressure dependent inlet flow
 

As I am solving a transient simulation of an inlet flow in a constant volume tank, super- and subsonic, I need to adabt the inlet velocity at the inlet boundary corresponding to the backpressure in the constant volume tank. Does anybody know how the expression need to be set in the CFX-Pre expressions? Something like mean(pressure)@domain

SomeVelocityFunction[m/s] * ave(Pressure)@domain/1[Pa]

Thank you evelica for your good answer. It works, finally.