Question

The induced angle of attack in terms of flow parameters for a wing is_____

(a) αi=\(\frac {w}{V_∞}\)

(b) αi=\(\frac {2w}{V_∞}\)

(c) αi=\(\frac {V_∞}{w}\)

(d) αi=\(\frac {w}{V_∞}\)

The question was asked at a job interview.

This is a very interesting question from Prandtl’s Classical Lifting-Line Theory in portion Flow over Airfoils over Finite Wing of Aerodynamics

Answer 1

The correct choice is (a) αi=\(\frac {w}{V_∞}\)

To elaborate: The induced angle of attack at an arbitrary position along span, for a finite wing can be given as αi=\(\frac {w}{V_∞}\) where V∞ is the free-stream velocity and w is the downwash (modulus only).