What is Manning Equation?

Manning Equation helps to calculate the open channel flow or sometimes used in pipe flow. The formula we use here is to help calculate the open channel flow when pressure drops due to friction in water piping systems.

General Information

The Manning formula is known in Europe as the Gauckler–Manning formula, or Gauckler–Manning–Strickler formula. In the United States, is Known as Manning’s equation.

It was first introduced by the French specialist Philippe Gauckler in 1867, and later re-created by the Irish architect Robert Manning in 1890.

The Manning Formula uses the Manning Index n or roughness coefficient which rely on the type and internal condition
of the pipe.

What is the Manning Equation in US Units

Where,

Where, R = D/4 (Circular Pipes)

D is inside diameter of pipe in ft

What is the Manning Equation in SI Units

Where,

Where, R = D/4 (Circular Pipes)

D is inside diameter of pipe in m

References

1. E. Shashi Menon, P.E., Piping Calculations Manual, 2005, McGraw-Hill

Other Equations may be of interest Colebrook–White | Darcy-Weisbach | Hazen Williams

Pipe Friction Factor App for Android Mobiles