I think that you must be a length of pipe. if you want to know that flow passes through an outlet or orifice plate length but need not exit diameter and in that case I recommend the soft instrucalc. to an outlet of a tank using ecuciones departing from the equation of Theorem bbernoulli and then corrected by several factors. hpe it helps
Here are few sites that can answer your question. http://www.1728.com/flowrate.htm http://www.pipeflowcalculations.com http://www.engineeringtoolbox.com/pi...stems-t_6.html Hope it helps. Regards, Zoran