I am a hydraulics student and have a question, hoping someone here could help me out. In my specific assignment i am required to determine D of a pipe without the friction factor using moody diagram and the darcy-weisbach equation. here is the exact question: A steel pipe (e=0.065mm) 4200m long is to convey oil (kinematic viscosity=5.2x10^-5 m/s^2) at 300 L/s from a resevior with surface elev. 247m to one with surface elev 156m. Theoretically, what pipe diameter size is required? All the prof says is Iteration is required to find pipe diameter, but i cannot figure out what the process is to guess and check. when do i know i have the right answer? Any thoughts? anybody? Thanks!