Hi everyone, Hoping someone can point me in the right direction. I'm trying to find (a theoretical approximation of) the flow rate through a pipe where the pressure is provided by an axial flow impeller, but restricted by an orifice plate. I have (or can get hold of) all the physical parameters - pipe dimensions, motor power, impeller power number, impeller pressure drop, pumping capacity, orifice area, etc..). I know the flow rate through the open pipe with no orifice plate. I imagine placing an orifice plate over the open pipe will create a higher pressure, more drag, put more load on the motor and reduce the flow rate. How will I find out the new flow rate? I guess I need to somehow find the new pressure difference either side of the orifice plate. I don't know how to do this. Any ideas/suggestions/equations/text book references would be a great help! Thanks!