THE FORCES ACTING ON AN AEROFOIL OF APPROXIMATE JOUKOWSKI TYPE IN A STREAM BOUNDED BY A PLANE WALL

Abstract

The investigation of the manner in which the effect of the ground on the lift and moment of an aerofoil is modified by its thickness and camber is of great interest not only from the theoretical point of view but also from the practical standpoint. In this paper we discuss in detail the modifications introduced by the thickness of an aerofoil on the ground-effect upon its lift, by evaluating the forces acting on some aerofoils (especially approximately symmetrical aerofoils) of approximate Joukowski type placed in a stream bounded by an infinite plane wall. It is found that when an aerofoil is placed in the vicinity of the ground at the small angles of attack used in practice, the lift on the aerofoil is in general increased by the presence of the ground, but the rate of increase of the lift becomes smaller as the thickness of the aerofoil increases.