Question

Given an angle of attack 5° and c = 5m, the moment coefficient about the leading edge is_____

(a) -0.137

(b) -0.685

(c) -7.8

(d) -0.27

The question was asked in an interview for internship.

My question is based upon The Symmetric Airfoil in chapter Incompressible Flow over Airfoils of Aerodynamics

Answer 1

Right option is (a) -0.137

The best I can explain: The coefficient of moment about the leading edge is given by cm,le=-π \(\frac {\alpha }{2}\) where α is in rad. It is independent of chord length.