Question

A 2D airfoil is operating at 0.6M. Find the approximate value of lift curve slope in per rad.

(a) 7.85

(b) 1.9

(c) 2.3

(d) 3.87

I got this question during an internship interview.

This interesting question is from Aerodynamics in portion Aerodynamics of Aircraft Design

Answer 1

Correct option is (a) 7.85

Easiest explanation: Given, mach number M = 0.6

2D lift curve slope = 2*π / (1-M^2)^0.5

= 2*π / (1-0.6^2)^0.5 = 7.85 per rad.