# Darcy Weisbach equation (head loss)

## Description

In fluid dynamics, the Darcy–Weisbach equation is a phenomenological equation, which relates the head loss — or pressure loss — due to friction along a given length of pipe to the average velocity of the fluid flow.

Darcy friction factor can be found from a Moody diagram

## Variables

h_{f} | Head loss (m) |

f_{D} | Darcy friction factor (see diagram) (dimensionless) |

L | Length of the pipe (m) |

D | Hydraulic diameter (m) |

V | Average velocity of the fluid flow (m/s) |

g | Standard gravity |

## Categories

### External links