A review of explicit approximations of Colebrook's equation

Abstract

The most common explicit correlations for estimation of the friction factor in rough and smooth pipes are reviewed in this paper. Comparison of any friction factor equation with the Colebrook's equation was expressed trough the mean relative error, the maximal positive error, the maximal negative error, correlation ratio and standard deviation. The statistical comparison of different equations was also carried out using the 'Model selection criterion' and 'Akaike Information Criterion'. It was found that the equation of Zigrang and Sylvester provides the most accurate value of friction factor, and that Haaland's equation is most suitable for hand calculations.

Keywords

• colebrook's equation
• friction factor
• approximations
• fluid mechanics
• turbulent flow