The 'Reynold''s number' at which transition from laminar to turbulent flow occurs in a pipe is approximately:
Choose the correct answer
Re = 100 (very low)
Re ≈ 2300 for pipe flow — below: laminar (f=64/Re); above 4000: turbulent (Colebrook-White)
Re = 10,000 always
Re = 1,000,000
Correct Answer
B. Re ≈ 2300 for pipe flow — below: laminar (f=64/Re); above 4000: turbulent (Colebrook-White)
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Critical Reynolds number for pipe flow: Re_crit ≈ 2300 (below: laminar, Hagen-Poiseuille); 2300–4000: transition (unstable); > 4000: turbulent. For open channels: use hydraulic radius R_h, Re_crit ≈ 500–2000. Re = ρVD/μ = VD/ν. Laminar: f = 64/Re (Darcy friction factor). Turbulent: Colebrook-White (Moody diagram). In practice: most waterworks pipelines operate at Re > 10,000 (fully turbulent).
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