The lift and stalling characteristics of a 35 deg. swept back wing designed to have identical chordwise pressure distributions at all spanwise stations when near maximum lift

Abstract

A 35 deg. swept back wing of aspect ratio 7 has been designed so that, according to the R.A.E. Standard Method, the planform gives a constant spanwise CL distribution, whilst the camber and twist distributions, coupled with local thickness modifications, combine to provide identical chordwise pressure distributions at all spanwise stations at an overall C L of 0.8. At mid-semi span the aerofoil section normal to the mean sweep line was a 12.2 per cent thick R.A.E. 100, and the design CL was chosen to be close to the maximum values obtained experimentally for this section. Overall forces, flow visualization, and detailed pressure plotting tests were conducted on this model at three Reynolds numbers. The pressure plotting results showed that the theoretical loading was quite closely attained except close to the leading edge near the root and out towards the tip. Very high peak suctions were observed near the leading edge within the inboard 10 per cent of the span, and these tended to dominate the stall behaviour of the wing. Nevertheless, it was possible to identify swept wing versions of the various classifications of two-dimensional stall pattern, and a good correlation was obtained between the sectional CLmax figures attained in two-dimensional flow and in the mid-semi span region.