Question

For a fluid initially at rest, the formation of starting vortex implies ______

(a) generation of lift

(b) generation of circulation

(c) generation of lift and circulation

(d) no lift is produced

This question was addressed to me in exam.

Question is taken from Kelvin’s Circulation Theorem and the Starting Vortex topic in portion Incompressible Flow over Airfoils of Aerodynamics

Answer 1

Right answer is (c) generation of lift and circulation

To explain I would say: From Kelvin’s Theorem, circulation remains constant with time. So for initial zero circulation, the formation of starting vortex means there has to be equal and opposite circulation in the form of lift.