Swamee-Jain Equation

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	\(\large{ dimensionless }\)