(2010年)管道长度L不变，管中流动为层流，允许的水头损失hf不变，若直径d变为原来的2倍时，且不计局部损失，流量将变为原来的( )倍。
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(2008年)边界层分离的必要条件是( )。
A. 来流流速分布均匀
B. 有逆压梯度和物面黏性阻滞作用
C. 物面形状不规则
D. 物面粗糙
Questions 22 to 25 are based on the passage you have just heard.
A. Juniors.
B. Seniors.
C. Would-be sophomores.
D. Graduates.
(2008年) 明渠均匀流的流量一定，渠道断面形状、尺寸和壁面粗糙一定时，正常水深随底坡增大而( )。
A. 增大
B. 减小
C. 不变
D. 不确定
Questions 22 to 25 are based on the passage you have just heard.
A. They have to live in dormitories of other universities.
B. They have to share dormitories with more roommates.
C. They have to live off campus.
D. They have to exchange dormitories with freshmen.
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