ESTIMATI0N 0F TIHE IS0BAR PATTERN 0N SWEPT WINGS

Abstract

Both experiments and theory indicate that in a three-dimensional flow near the centre of a swept-back wing, the point of minimum pressure is shifted backwards from the leading edge.  Hence the local lift in the front of the centre section is reduced compared with that of the flat-plate, while the local lift on the rear part has a somewhat higher value. The maximum local velocity of the flow across the centre section is not necessarily higher compared with that of the sections located at greater distances from the kink.  The available methods for estimation of the velocity distribution in centre section of swept wings are restricted to the case of zero lift.  This note represents an attempt to illustrate a way for determination of an approximate velocity distribution and the isobar pattern in the region of the plane of symmetry including the cases of non-zero lift.  Simple expressions are given for calculating the chord wise velocity distributions both for the centre section and the sections at greater spanwise distances from the kink.  Assuming a parabolic span-wise variation of isobars in the region adjacent to the plane of symmetry, a method that can be used to predict the isobar pattern is briefly demonstrated for two particular swept-back and swept-forward constant chord wings with symmetrical airfoils for two values of the local lift.  Since the resultant isobar pattern obtained in this way is only approximate and of empirical character, a firmer theoretical basis is needed.