Question:-
Flow separation is caused by
Option (A)
Reduction of pressure to local vapour pressure
Option (B)
A negative pressure gradient
Option(C)
A positive pressure gradient
Option(D)
Thinning of boundary layer thickness to zero
Correct Option:
(C)
Question Solution:
When the pressure goes increasing {(P/ x) > 0} in the direction of flow, the pressure force acts against the direction of direction of flow thus retarding the flow in the boundary layer and hence thickenings the boundary layer more rapidly. This and the boundary shear bring the fluid in the boundary layer to rest and causes back flow. Due to this the boundary layer no more sticks to the boundary but is shifted away from the boundary. This phenomenon is called as “ Boundary layer separation”.
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