Low-speed wind-tunnel measurements on a thin sharp-edged delta wing with 70 degrees leading-edge sweep, with particular reference to the position of leading-edge-vortex breakdown

Abstract

The position of the breakdown of the tightly rolled leading-edge vortex was observed Using a smoke technique. The breakdown point moved forward with increasing incidence, and reached a point above the trailing edge at an incidence of 32°. It moved forward to transverse planes through 0.5 and 0.28 of the centreline chord at 34° and 37° incidence respectively. The root-mean-square intensity and the low-frequency component of pressure fluctuations both began to rise rapidly at approximately the same incidence (31°) at four widely spaced points on the wing. This rise in pressure fluctuations was accompanied by a similar increase in the low-frequency component of normal-force fluctuations. The lift slope decreased at incidences above 21°, coinciding with a marked decrease in longitudinal stability. The drag coefficient varied linearly with CL² up to an incidence of about 24°.