A nozzle is a tapering mouthpiece which is fitted to the end of a water pipe line to discharge water at a high velocity. A nozzle is generally made of convergent shape. The power transmitted through the nozzle is maximum when the head lost due to friction in the pipe is one-third of the total supply head at the inlet of the pipe. The diameter of the nozzle (d) for maximum transmission of power is given by

 where

D = Diameter of pipe,

f = Darcy’s coefficient of friction for pipe, and

l = Length of pipe.