Friction Factor

Calculate the Darcy–Weisbach friction factor in a system

Fluid Properties

Piping Properties

Answer

unitless
unitless
unitless
unitless

Governing Equation

Laminar flow:

The friction factor is easily determined for the laminar flow regime

fd=64Ref_d = \frac{64}{Re}

The Colebrook–White equation:

If the flow regime is not laminar, a more complicated equation is used to iteratively solve for the friction factor.

fd=1−2log10(ϵ3.7di+2.51Ref)2f_d = \frac{1}{ -2log_{10} \left( \frac{\epsilon}{3.7 d_{i}} + \frac{2.51}{Re\sqrt{f}}\right )}^{2}

This equation must be solved iteratively until convergence.

Fanning friction factor

The Darcy–Weisbach friction factor should not be confused with the Fanning friction factor which is 4 times smaller.

f=fd/4f = f_d / 4

Definitions

fd=f_d =
Darcy friction factor
f=f =
Fanning friction factor
Re=Re =
Reynolds Number
di=d_i =
Inner pipe diameter
ϵ=\epsilon =
Surface roughness