A.僅與雷諾數(shù)有關(guān) B.僅與相對粗糙度有關(guān) C.與雷諾數(shù)及相對粗糙度有關(guān) D.是常數(shù)
A.1 B.2 C.3 D.4
A.2∶1 B.1∶1 C.1∶2 D.1∶4