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【单选题】
有一个变直径管流,直径 d 1 ,大管直径 d 2 =2 d 1 ,则断面雷诺数的关系是 ( )A.
Re 1 =0.5 Re 2
B.
Re 1 = Re 2
C.
Re 1 =1.5 Re 2
D.
Re 1 =2 Re 2
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