Question

What is the value of angular velocity at a point on the solid surface outside the boundary layer where the velocity becomes equal to free stream velocity?

(a) Infinite

(b) One

(c) Zero

(d) 0.5

I had been asked this question in class test.

The above asked question is from Irrotational Flow in portion Velocity Potential Equation of Aerodynamics

Answer 1

Right answer is (c) Zero

The explanation: When the fluid flows towards a solid surface, there is a boundary layer formation with zero velocity at its surface and as we proceed normally, it increases to finally become equal to the free stream velocity. At this particular point there is no vorticity i.e. the flow is irrotational. For an irrotational flow the angular velocity is zero.