# Friction Loss

Written by Jerry Ratzlaff on . Posted in Classical Mechanics

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

 $$\large{ FL = C \; \frac{ Q }{ 100 }^2 \; \frac{ l }{ 100 } }$$ $$\large{ FL = C \; Q_1^2 \; l_1 }$$

### Where:

 Units English Metric $$\large{ FL }$$ = friction loss $$\large{ lbf }$$ $$\large{ N }$$ $$\large{ l }$$ = length of pipe $$\large{ ft }$$ $$\large{ m }$$ $$\large{ l_1 }$$ = length of pipe / 100 $$\large{ ft }$$ $$\large{ m }$$ $$\large{ Q }$$ = flow rate $$\large{\frac{ft^3}{sec}}$$ $$\large{\frac{m^3}{s}}$$ $$\large{ Q_1 }$$ = flow rate / 100 $$\large{\frac{ft^3}{sec}}$$ $$\large{\frac{m^3}{s}}$$ $$\large{ C }$$ = friction loss coefficient $$\large{ dimensionless }$$

## Related formulas

 $$\large{ FL = \frac{ h_l }{ l } }$$ (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

$$\large{ p_c }$$ = pressure change

$$\large{ v }$$ = velocity of fluid 