The 'Moody diagram' relates the friction factor f to:
Choose the correct answer
Only pipe material and pressure
Reynolds number Re and relative roughness ks/D — determines Darcy friction factor for all pipe flow regimes
Only flow velocity and pipe diameter alone
Pipe age and corrosion category
Correct Answer
B. Reynolds number Re and relative roughness ks/D — determines Darcy friction factor for all pipe flow regimes
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Moody diagram: plot of Darcy-Weisbach friction factor f vs. Reynolds number Re for different relative roughness (ks/D) values. Regions: (1) Laminar (Re < 2000): f = 64/Re (straight line, independent of roughness); (2) Transition (2000–4000): unstable; (3) Turbulent smooth (Blasius); (4) Fully rough turbulent: f depends only on ks/D (independent of Re); (5) Transition turbulent: Colebrook-White equation covers this. Essential tool for pipe hydraulics.
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