# Friction Loss

Friction loss, abbreviated as FL, is how much loss of flow through a pipe is due to the viscosity, the measure of the internal friction/resistance to the flow of a liquid near the surface of the pipe.

## Friction Loss formulas

\(\large{ FL = C \; \frac{ Q }{ 100 }^2 \; \frac{ l }{ 100 } }\) | |

\(\large{ FL = C \; Q_1^2 \; l_1 }\) | |

\(\large{ FL = \frac{ h_l }{ l } }\) | (hydraulic slope) |

\(\large{ FL = \frac{ 1 }{ \rho \; g } \; \frac{ p_c }{ l } }\) | (hydraulic slope) (related to pressure change) |

\(\large{ FL = \frac{ 64 \; \nu }{ 2 \; g } \; \frac{ v }{ d^2 } }\) | (laminar flow) |

### Where:

\(\large{ FL }\) = friction loss

\(\large{ \rho }\) (Greek symbol rho) = density of fluid

\(\large{ g }\) = standard gravity

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

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

\(\large{ \nu }\) (Greek symbol nu) = kinematic viscosity

\(\large{ l }\) = length of pipe

\(\large{ l_1 }\) = length of pipe / 100

\(\large{ Q }\) = flow rate

\(\large{ Q_1 }\) = flow rate / 100

\(\large{ C }\) = friction loss coefficient

\(\large{ p_c }\) = pressure change

\(\large{ v }\) = velocity of fluid