The Lift On the Symmetrical Joukowski Aerofoil in a Stream bounded by a Plane Wall

Abstract

In this paper the lift on the symmetrical Joukowski aerofoil of small thickness in the presence of a plane rigid wall is obtained in the form of a power-series, with the intention of discussing the manner in which the ground-effect on the lift of an aerofoil is modified by its thickness. The calculation of the lift is carried out by extending Green's analysis. It is found that in case when the symmetrical Joukowski aerofoil of small thickness is placed in the vicinity of the wall at small angles of attack as used in practice, the wall-effect on the lift is quite similar to that in the case of a plane aerofoil. Namely, as the symmetrical Joukowski aerofoil approaches the wall, the lift first decreases and then tends to increase to values which are greater than the corresponding values for the symmetrical Joukowski aerofoil in an infinite stream, especially when the angle of attack is sufficiently small. Further it is found that for any value of the distance of the aerofoil from the wall, the lift ratio Y / Y 0 decreases as the thickness increases even for small values of the angle of attack.