Question

How is supercritical airfoil different from the NACA 64 series airfoil?

(a) Thinner airfoil

(b) Less cambered

(c) Flatter top surface

(d) Flatter lower surface

I have been asked this question in semester exam.

My enquiry is from The Supercritical Airfoil topic in division Subsonic Compressible Flow over Airfoils : Linear Theory, Linearized Supersonic Flow of Aerodynamics

Answer 1

Correct option is (c) Flatter top surface

Explanation: The supercritical airfoils have a flatter top surface compared to the NACA 64 series airfoil. This leads to lesser local Mach values at the top even when it is at supersonic speed. In turn, there is a weaker terminating shock leading to less drag.