# Swamee-Jain Equation

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

The Swamee-Jain Equation can be used to solve the Darcy-Weisbach friction factor for a full-flowing pipe and is accurate to 1.0% of the Colebrook-White Equation for  $$10^{-6} < \frac{\epsilon}{d} < 10^{-2}$$  and  $$5,000 < Re < 10^8$$.

## swamee-jain equation formula

$$\large{ f = \frac{0.25}{[log \; (\frac{\epsilon}{3.7\;d} + \frac{5.74}{Re^{0.9}})]^2} }$$
Symbol English Metric
$$\large{ f }$$ = friction factor $$\large{ dimensionless }$$
$$\large{ \epsilon }$$  (Greek symbol epsilon) = absolute roughness $$\large{ in }$$ $$\large{ mm }$$
$$\large{ d }$$ = inside diameter of pipe $$\large{ in }$$ $$\large{ mm }$$
$$\large{ Re }$$ = Reynolds number $$\large{ dimensionless }$$