变直径管流，细断面直径为d1=30mm,雷诺数为5000,粗断面直径d2=2d1,则粗断面管中雷诺数是（）。A. 5000 B. 4000 C. 2...

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问题变直径管流，细断面直径为d1=30mm,雷诺数为5000,粗断面直径d2=2d1,则粗断面管中雷诺数是（）。

选项 A. 5000 B. 4000 C. 2500 D. 1250

答案 C

解析

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