Low-speed measurements of the pressure distribution at the surface of a swept-back wing

Abstract

Low-speed measurements of the pressure distribution have been made at selected stations on a swept-back wing with and without body. The wing was of 45 deg sweep-back, with a sharp discontinuity at the centre-section, and of aspect ratio 3 with uniform chord. The aerofoil section was chosen to be suitable for work at low Reynolds number, and the wing plan to be of the maximum utility for comparison of observed and calculated pressure distribution. The work is the first part of a programme designed to give results of the greatest assistance to the development of mathematical methods, and the model was of exceptionally clean design to avoid extraneous effects. The symmetry of the model allowed the work to be duplicated by coveIing a range of positive and negative incidences, and by averaging, it has been possible to remove zero irregularities due to wind-tunnel flow and present accurate values of pressure distribution, distribution of local lift coefficient and centre of pressure of normal force for a range of incidence 0 to 16 degrees. Wind-tunnel balance measurements of overall lift appear to be in reasonable agreement with the pressure plots. A selection of chordwise pressure distributions is plotted and it is shown that at zero lift for the wing along there is good agreement with curves calculated at the Royal Aircraft Establishment. A comparison of a potential solution for load grading and local aerodynamic chord with the wind-tunnel measurements at finite lift shows approximately the variation due to the effects of wing thickness and viscosity.