Comparison of Three Methods for the Evaluation of Subsonic Lifting-Surface Theory

Abstract

Independent numerical methods for obtaining the subsonic load distribution on a thin wing of arbitrary twist and camber have been developed at NPL, NLR (Netherlands) and BAC (Warton), The three methods have been studied jointly and their novel features have been reviewed critically. The best solutions by each method show excellent agreement for wings, at uniform incidence, having smooth leading and trailing edges. Spanwise loading, local aerodynamic centres, lift, pitching moment, vortex drag and chordwise loadings are tabulated for circular and rectangular planforms, for a wing of constant chord with hyperbolic leading and trailing edges, and for a tapered sweptback wing. The convergence of the solutions is examined in detail with respect to separate parameters representing the numbers of spanwise integration points and spanwise and chordwise collocation points. The tapered sweptback planform is considered with different amounts and types of artificial central rounding, but the crucial problem of a central kink under lifting conditions remains a subject for research.