The implicit ColebrookWhite equation has been widely used to estimate the friction factor for turbulent fluid flow in roughpipes. In this paper, the stateoftheart review for the most currently available explicit alternatives to the ColebrookWhite equation, is presented. An extensive comparison test was established on the grid, for a wide range of and R values ( ; ), covering a large portion of turbulent flow zone in the Moody’s diagram. Resulting from the comprehensive error analysis, the magnitude points in which the maximum absolute and the maximum relative error are occurred at the pair of and R values, are also examined. A limiting case of the most of these approximations provided friction factor estimates that are characterized by a mean absolute error of , a maximum absolute error of whereas, a mean relative error of 1.3% and a maximum relative error of 5.8%, over the entire range of and R values, respectively. For practical purposes, the complete results for the maximum and the mean relative errors versus the 20 sets of value, are also indicated in two figures. The extensive comparison test gives an opportunity to practically evaluate the most accurate equation among of all the previous explicit models; and showing in this way its great flexibility for estimating turbulent flow friction factor. Comparative analysis for the mean relative error profile clearly indicated, the classification for the bestfitted 6 equations examined was in a good agreement with those of the best model selection criterion, presented in the literature.
Anahtar Kelimeler: Fluid flow, riction, Turbulent flow, Friction factor, Closed form solutions, Excel spreadsheet; Techdig 2.0.
