New Formulae for Water Flow in Pipes *

Abstract

As a result of extensive investigation of water flow formulae and test data on water mains and experimental test pipes, four new formulae for water flow in pipes have been evolved. These apply to pipes in new condition using water at normal temperatures, and cover all classes and sizes of pipes and a very wide range of velocities. The constants in the formulae do not require to be varied to suit the condition or the size of pipe. It is only necessary to choose the appropriate formula to suit the material of which the internal surface of the pipe is made. These four formulae are:—

1. (1)

For smooth non-ferrous pipes: V = 47m***^0·71i^0·57.

(2)

For bare steel, wrought iron, asbestos cement, or bitumen lined pipes: V = 40m^0·69i^0·555.

(3)

For bitumen coated steel pipes or concrete pipes: V = 36m^0·68i^0·54.

(4)

For galvanized cast iron, or other coated cast iron pipes: V = 30^0·67i^0·52.

An approximate estimate of the conditions arising when fluids other than water are used can be obtained by plotting these formulae on a Reynolds number diagram, and taking the value of F at the appropriate Reynolds number, but this is not recommended, since these formulae have not been compared with practical test results for fluids other than water.

The use of these formulae will give the discharge to be expected from any class and size of pipe to an error of not more than about ±10 per cent. Such accuracy is adequate for all ordinary water flow calculations, and is better, over the whole range of pipe surfaces, sizes, and velocities, than has been previously possible by the use of any other formula.