An experimental investigation of the effects of deformation on the aerodynamic characteristics of a swept-back wing

Abstract

A wind-tunnel investigation of the effects of structural deformation on the pressure distributions round a tapered wing, with 44-deg leading-edge sweepback, has been carried out over a range of deformations at a Reynolds number of 0.6 x 10power6. A technique for constructing a model and deforming it into any desired deformation has been successfully developed. The model is made of Perspex which becomes plastic at 100 deg C.; after being boiled in a water bath the model can be deformed into any desired deformation, and on cooling, it sets hard with the deformation 'frozen' in. When the model is boiled again it reverts to its undeformed shape and a new deformation can then be applied while it is in its plastic state. The cycle can be repeated any number of times with the same model, to cover a range of deformations. From the modes investigated the appropriate deformations required to produce an almost elliptic span loading at a selected moderate overall lift, or to delay tip stalling at high incidence, were established. The most important feature is to have a maximum wash-out at about 0.7 semi-span, with a decrease of wash-out from there to the tip, and not a continuously increasing wash-out right to the tip. The Weissinger method for theoretical prediction of airloads was found to be reasonably satisfactory for the effect of deformation at low incidence.