# Darcy friction factor - Blasius correlation

## Description

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.

Early approximations for smooth pipes by Paul Richard Heinrich Blasius in terms of the Moody friction factor are given in one article of 1913 and calculated as shown here.

Johann Nikuradse in 1932 proposed that this corresponds to a power law correlation for the fluid velocity profile.

Related formulas## Variables

f | Darcy friction factor (dimensionless) |

Re | Reynolds number (dimensionless) |