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The Colebrook equation $\zeta$ is implicitly given in respect to the unknownflow friction factor $\lambda$; $\lambda=\zeta(Re,\epsilon^*,\lambda)$ whichcannot be expressed explicitly in exact way without simplifications and use ofapproximate calculus. Common approach to solve it is through the Newton-Raphsoniterative procedure or through the fixed-point iterative procedure. Bothrequires in some case even eight iterations. On the other hand numerous morepowerful iterative methods such as three-or two-point methods, etc. areavailable. The purpose is to choose optimal iterative method in order to solvethe implicit Colebrook equation for flow friction accurately using the leastpossible number of iterations. The methods are thoroughly tested and thosewhich require the least possible number of iterations to reach the accuratesolution are identified. The most powerful three-point methods require in worstcase only two iterations to reach final solution. The recommendedrepresentatives are Sharma-Guha-Gupta, Sharma-Sharma, Sharma-Arora,D\v{z}uni\'c-Petkovi\'c-Petkovi\'c; Bi-Ren-Wu, Chun-Neta based on Kung-Traub,Neta, and Jain method based on Steffensen scheme. The recommended iterativemethods can reach the final accurate solution with the least possible number ofiterations. The approach is hybrid between iterative procedure and one-stepexplicit approximations and can be used in engineering design for initialrough, but also for final fine calculations.

Choosing the optimal multi-point iterative method for the Colebrook flow friction equation -- Numerical validation