Some notes on the zero-lift wave drag of slender wings with unswept trailing edge

Abstract

Minimum values of the zero-lift wave drag of slender wings with certain fixed properties have been calculated by slender-body theory. The cross-sectional area distributions of the wings are taken to be polynomials and the fixed properties of the wings correspond to fixed first and second derivatives of the area distributions at the apex and rear end. The drag for delta wings of rhombic cross sections has also been calculated by thin-wing theory without the slenderness assumption. Comparisons between the drag coefficients calculated by both theories have been made for a series of wings to investigate the applicability of slender theory. The calculations by both theories suggest that it should be possible to design thickness distributions which have drags as low as that of the so-called Lord V area distribution on plan-forms for which the Lord V distribution is unsuitable. Further, this can be achieved when the thickness near the apex and the slope at the trailing edge are restricted.