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# Haaland equation

The Haaland equation is an approximate explicit equation which combines experimental results of studies of laminar and turbulent flow in pipes. It was developed by S. E. Haaland in 1983.

$\frac{1}{\sqrt {f}} = -1.8 \log \left[ \left( \frac{\varepsilon/D}{3.7} \right)^{1.11} + \frac{6.9}{\mathrm{Re}} \right]$