ABSTRACT
These equations for A are very accurate, being the result of many very precise experiments in several laboratories. The problem is that /I is a function of Reynolds number Re, i.e. fluid velocity, which is not known at the beginning of the computation. Further unknowns are the actual roughness of the pipe, k, and the internal diameter of the pipe, d, after several years of service when the net flow area could be significantly reduced due to deposits and encrustation.
