The nozzle discharge coefficient Cd is defined as the II!ratio of the actual mass flow rate through the nozzle to i! the ideal mass flow rate based on one-dimensional isentropic flow consideration.
An impact tube can be used to infer local velocity. It is assumed that the fluid is brought to a complete stop inside the tube (VIT = 0) and the conversion of kinetic energy to pressure energy is ideal:
A traverse of the cross-sectional area with the impact tube is required to obtain the velocity distribution and hence an estimate for average stream velocity (refer to the above schematic).