# Darcy Friction Factor

Darcy friction factor, abbreviated as \(f_d\), a dimensionless number, also called Darcy-Weisbach friction factor, formulas are equations that help calculate the friction losses in pipe flow and open channel flow. This coefficient is used in the Darcy-Weisbach equation.

Fanning friction factor is not the same as the Darcy friction factor. It is equal to 1/4 the Darcy friction factor. Since they are basically the same, you need to note which one is being used when doing calculations. Use \(f_f\) or \(f_d\) for the Fanning or Darcy friction factor, respectively.

## Article Links

- Darcy Friction Factor - Brkic - Determination of the Darcy friction factor using the Brkic method.
- Darcy Friction Factor - Free Surface Flow - Darcy friction factor for pipe flow and open channel flow.
- Darcy Friction Factor - Laminar Flow - Darcy friction factor for laminar flow.

## Darcy friction factor formula

\(\large{ f_d = \frac { 2 \; h_l \; d \; g } { l_p \; v^2 } }\) |

### Where:

\(\large{ f_d }\) = Darcy friction factor

\(\large{ g }\) = gravitational acceleration

\(\large{ h_l }\) = head loss

\(\large{ l_p }\) = lenght of pipe

\(\large{ v }\) = mean flow velocity

\(\large{ d }\) = pipe inside diameter