Question

Flow separation causes lift to decrease with increasing angle of attack. This is inconsistent with the thin airfoil theory where the lift curve slope is 2π. This is a contradiction.

(a) True

(b) False

This question was posed to me during an online interview.

My enquiry is from Viscous Flow in chapter Incompressible Flow over Airfoils of Aerodynamics

Answer 1

Correct choice is (b) False

To explain I would say: The thin airfoil theory assumes the angle of attack is small. Moreover, flow separation occurs for high angle of attack, for angles greater than the critical angle of attack (which is generally over 12°) where stall occurs leading to reduction of lift. So this is not a contradiction.