# Fanning Friction Factor

on . Posted in Dimensionless Numbers

Fanning friction factor, abbreviated as f, a dimensionless number, is used in fluid dynamics to quantify the amount of frictional resistance encountered by a fluid flowing through a pipe or conduit.  In many practical engineering applications, the Fanning friction factor is used to calculate the pressure drop or head loss in a pipe due to friction.  It plays a crucial role in the design and analysis of piping systems, as it affects the energy required to pump a fluid through a pipe and influences the efficiency of fluid transportation.

The Fanning friction factor depends on several factors, including the type of fluid, the Reynolds number, and the roughness of the pipe wall.  It is commonly determined experimentally or estimated using empirical correlations and charts for specific flow conditions and pipe geometries.  The choice of an appropriate friction factor model depends on the specific fluid and pipe characteristics of the system being analyzed.

### Fanning friction factor formula

$$f \;=\; \tau \;/\; \rho \; (Q^2\;/\;2)$$
Symbol English Metric
$$f$$ = Fanning friction factor $$dimensionless$$
$$\rho$$  (Greek symbol rho) = density of fluid $$lbm\;/\;ft^3$$ $$kg\;/\;m^3$$
$$\tau$$  (Greek symbol tau) = shear stress $$lbf\;/\;in^2$$  $$Pa$$
$$Q$$ = velocity of bulk flow $$ft\;/\;sec$$ $$m\;/\;s$$

### Fanning friction factor formula

$$f \;=\; 16 \;/\; Re$$     (Fanning Friction Factor)

$$Re \;=\; 16 \;/\; f$$

Symbol English Metric
$$f$$ = Fanning friction factor $$dimensionless$$
$$Re$$ = Reynolds number $$dimensionless$$