Calculation of the induced velocity field on and off the wing plane for a swept wing with given load distribution

Abstract

Computer programs have been written to evaluate the integrals of lifting-surface theory for the velocity field of a thin wing with given load distribution. Different programs are used for the downwash at points on the wing, and for any or all three velocity components off the wing. The heart of the programs is an analytic evaluation of the spanwise integral over a short line following the local sweep: by combining together a number of such integrals, the complete integral over the wing is built up. Both programs are tested by comparison with other results : exact linear theory for a two-dimensional fiat plate, a result of Garner for a rectangular wing, theory for an infinite swept wing with isobars kinked at the centre line, and comparison for a tapered wing with a pioneer program written by Freestone. The downwash program cannot compute the downwash at the apex of a swept wing with rounded isobars, nor exactly at a wing tip.