Question

What is the lift coefficient over a flat plate at an angle of attack of 3 degrees in a supersonic flow at Mach 4?

(a) 0.0512

(b) 0.0541

(c) 0.0628

(d) 0.0714

I got this question during an internship interview.

I would like to ask this question from Application to Supersonic Airfoils in section Subsonic Compressible Flow over Airfoils : Linear Theory, Linearized Supersonic Flow of Aerodynamics

Answer 1

Correct choice is (b) 0.0541

Easy explanation: Given, α=3 deg=0.05236 rad, M=4

The lift coeeficient formula according to the linearized theory is :

cl=\(\frac {4α}{\sqrt {M_∞^2-1}}\)

Substituting the values:

cl=\(\frac {4 × 0.05236}{\sqrt {4^2-1}}\)=0.0541