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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.

The Haaland equation is defined as:

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

where:

## References

• Haaland, SE (1983). "Simple and Explicit Formulas for the Friction Factor in Turbulent Flow". Trans. ASIVIE, J. of Fluids Engineering 103: 89-90.