Low-speed wind-tunnel experiments on a series of sharp-edged delta wings

Abstract

A series of six delta wings of varying angles of sweepback has been tested. A three-component strain-gauge balance was used to investigate the forces and moments, and normal-force fluctuations for incidences between ± 60°. Positions of vortex breakdown on these wings were noted. Surface flow pattern and boundary-layer transition observations were made. The three most highly swept wings (i.e. having sweepback angles of 65°, 70° and 76°) appeared to have the most favourable characteristics of growth of normal-force fluctuations and had a smooth variation of forces and moments throughout the incidence range between positive and negative stalls. The change from a vortex type of flow to one with complete flow reversal on the upper surface occurred at increased incidence with increase of sweepback angle. At moderate incidence α the main features of the flow pattern correspond to conical flow development, and correlate well with the single parameter α/cot φ, where φ is the sweepback angle of the leading edge.