These quantities are related by the Colebrook equation
Guessed relative roughness values were substituted successively into the Colebrook equation until the square of the difference of the calculated and experimentally determined friction factors approached zero.
The Colebrook equation was used to solve iteratively for the friction factor by means of a standard root-solving procedure.
The Colebrook equation was employed to evaluate the friction factor using an iterative approach for a range of duct diameters from 203 mm (8 in.
For a specified value of D, the friction factor f was calculated by means of the Colebrook equation.
FC] is the friction factor calculated using the Colebrook equation, and N is an iteration counter.
Hence if the determination of relative roughness by means of a solution to the Colebrook equation is based on measurements of pressure loss in a developing flow, it is evident that calculated values of [epsilon]/[D.
The relative roughness was determined iteratively by fitting the experimentally determined friction factors to the Colebrook equation using the least squares method: this approach is described in more detail in Idem et al.