Thin airfoil theory

Summary

Thin airfoil theory is a linear model of steady plane flow of an ideal fluid around a thin wing section. The section must have small camber and a small angle of attack. It replaces the airfoil by a sheet of vortices along its chord. This reduces the flow problem to the airfoil equation, a singular integral equation with an explicit solution. Its main prediction is that the lift coefficient is $2\pi$ times the angle of attack, measured from the zero-lift angle. For a symmetric section the lift acts at the quarter-chord point. These results agree well with experiments before stall and are the starting point of wing theory.