Further Studies on the Lift and Moment of a Circular Arc Aerofoil which touches the Ground with its Trailing Edge

Abstract

§7. As a supplement to our previous paper, additional numerical calculations have been carried out for the lift and moment coefficients of a circular arc aerofoil which touches the ground with its trailing edge, with a special intention of studying in detail the manner in which the lift and moment forces acting on such an aerofoil are affected by the presence of the ground. For this purpose, two special circular arc aerofoils have been taken; the camber of the arc aerofoil is about 0•022 while that of the other 0•053 approximately. The numerical calculations have been performed for various values ranging from 0° to 30° of the angle of attack. Also, the values obtained in our previous paper for one special circular arc aerofoil whose camber is 0•097 approximately have also been reproduced for the sake of comparison.
It has thus been found that for fairly small values of the angle of attack α (e.g. α=5°, 10°) which usually occur in practice, the lift and moment coefficients of a circular arc aerofoil are rather greater when the aerofoil touches the bounding wall with its trailing edge than when it is in an unlimited stream, provided that its camber is sufficiently small.
These results are not only of considerable theoretical interest in themselves, but also worthy of special notice in connection with the problem of the ground effect upon the lift and moment forces acting on a circular arc aerofoil which is placed in any position near the ground