Project ForgeFour candidate sets of Fanning friction factor data are given for Re=100(k/D=0), Re=1000(k/D=0.001), Re=1e5(k/D=0), Re=1e5(k/D=0.001): Set I: 0.16,0.016,16e-5,16e-5. Set II: 0.016,0.16,0.0055,0.0045. Set III: 0.16,0.016,0.0045,0.0055. Set IV: 0.0045,0.0055,0.016,0.16. Which set is correct?
- ASet I
- BSet II
- Set III
- DSet IV
Explanation
At laminar Re=100 and Re=1000, f=16/Re regardless of roughness (0.16 and 0.016), ruling out Sets II and IV. At turbulent Re=1e5, roughness must INCREASE f relative to the smooth case (Blasius gives ~0.0044 for smooth) — only Set III shows the smooth value (0.0045) lower than the rough value (0.0055); Set I's implausibly tiny 16×10⁻⁵ values are wrong.
Source: GATE CH 2017 (2017)
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