Darcy friction factor - Free surface flow


In fluid dynamics, the Darcy friction factor formulae are equations that allow the calculation of the Darcy friction factor, a dimensionless quantity used in the Darcy–Weisbach equation, for the description of friction losses in pipe flow as well as open-channel flow.

The Darcy friction factor is also known as the Darcy–Weisbach friction factor, resistance coefficient or simply friction factor; by definition it is four times larger than the Fanning friction factor.

The shown formula is another form of the Colebrook-White equation exists for free surfaces. Such a condition may exist in a pipe that is flowing partially full of fluid.

Related formulas


fDarcy friction factor (dimensionless)
ϵPipe's effective roughness height (m)
RhHydraulic radius (m)
ReReynolds number (dimensionless)