Darcy friction factor - Colebrook–White equation (relative to the radius)
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 phenomenological Colebrook–White equation (or Colebrook equation) expresses the Darcy friction factor f as a function of Reynolds number Re and pipe relative roughness ε / Dh, fitting the data of experimental studies of turbulent flow in smooth and rough pipes. The equation can be used to (iteratively) solve for the Darcy–Weisbach friction factor f.
For a conduit flowing completely full of fluid at Reynolds numbers greater than 4000, it is expressed as shown here.Related formulas
|f||Darcy friction factor (dimensionless)|
|ϵ||Pipe's effective roughness height (m)|
|Rh||Hydraulic radius (m)|
|Re||Reynolds number (dimensionless)|