Cl,0 ; it is how much efficient to calculate Cl,0 (i.e. Cl incompressible)

[Faizan Habib]

Cl,0 ; it is how much efficient to calculate Cl,0 (i.e. Cl incompressible) when the airfoil is thin, symmetrical, at alpha = 3 degrees and moving at low speed. Actuall it appeared in my compressible aerodynamics paper where i ha to calculate CL. I was given Lift per unit span, dynamic head q, in unites of N per m. I was also given chord length. So there were two ways to calculate Cl,o. one to use thin airfoil theory Cl,o = 2 * pi * alpha. But Cl,0 can also can be calculated from L/q. So please answer what was the right way to solve it and what is basic difference in both the ways as both gave different results.

 

[Navin A S]

The right way to calculate Cl,0 in this case is to use the formula Cl,0 = 2 * pi * alpha. This is because the airfoil is thin and symmetrical, which means that the lift force is mainly generated by the angle of attack, not by the camber of the airfoil. The formula L/q may be used when the lift force of an airfoil is generated by its camber, but this does not apply in this case.