Question:-
During the flow over a circular cylinder, the drag coefficient drops significantly at a critical Reynolds number of 2 x 105. this is due to
Option (A)
Excessive momentum loss in the boundary layer
Option (B)
Separation point travelling upstream
Option(C)
Reduction in skin-friction drag
Option(D)
The delay in separation due to transition turbulence
Correct Option:
(D)
Question Solution:
The drag coefficient remains practically constant until a Reynolds’s number of 2 x 105 is reached. At this stage the Cd drops steeply by a factor of 5. This is due to the fact that the laminar boundary layer turns turbulent and stays unseparated over a longer distance, then reducing the wake considerable
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