Improvement of the hydraulic friction losses equations for flow under pressure in circular pipes

Authors: Matej URŠIČ, Boris KOMPARE
Citation: Acta hydrotechnica, vol. 21, no. 34, pp. 57-74, 2003.
Abstract: Following the experiments of Nikuradse and construction of the Moody diagram the term for hydraulic losses in pipes got its final form in the Colebrook-White formula. Despite the fact that the formula was developed only for the fully turbulent flow it is used also for the transition and laminar flow. Comparisons between the characteristic formulas for the friction factor and Nikuradse's experimental results show the need to revise this formula for low Reynolds numbers (Re < 4000). Indeed, the revision is even more necessary when one deals with unsteady flow. In this paper, a construction of a new formula for the friction factor, which successfully combines theoretical background and empirical knowledge, is shown. This formula gives better fit to the measured friction factor than the results of classical (known) formulas. The formula sets the basis for further experiments, which will improve the friction factor formula in unsteady flow conditions.
Keywords: hydraulic losses, friction factor, relative roughness, parameter optimization, pipes, steady flow, Colebrook-White, Nikuradse, Moody
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