2012 Professional Knowledge Morning 55

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55. In the friction coefficient diagram, it is generally divided into 4 different regions. Which of the following statements is correct? A Laminar region: Re≤2000; λ is linearly related to Re, and it is independent of ε/d. B Transitional region: Re=2000~4000; for calculating flow resistance, it is safer to obtain the value of λ by extending the curve from the turbulent regime. C Turbulent region: Re=4000 and areas below the dashed line; in this region, λ is independent of Re but dependent on ε/d. D Fully turbulent region: Areas above the dashed line in the diagram; λ is dependent on ε/d and independent of Re. The answer is ABD. I have doubts regarding option A – whether it’s according to industry standards or those from Tianjin University, it is stated that in the laminar region (Re≤2000), λ=64/Re, and λ is independent of ε/d. With Re≤2000 and λ=64/Re, is λ still linearly related to Re? Is it not a hyperbola?