Serghidess solution is used to solve directly for the Darcy–Weisbach friction factor f for a full-flowing circular pipe.  It is an approximation of the implicit Colebrook–White equation. It was derived using Steffensens method.
The solution involves calculating three intermediate values and then substituting those values into a final equation.
The equation was found to match the Colebrook–White equation within 0.0023% for a test set with a 70-point matrix consisting of ten relative roughness values (in the range 0.00004 to 0.05) by seven Reynolds numbers (2500 to 10).