Performance effects of a single tubercle terminating at a swept wing’s tip

Abstract

This study investigates the effects of a single tubercle terminating at a swept wing’s tip on its performance at pre-stall angles of attack (AOAs). Two tubercle geometries with amplitudes of 10.5mm and wavelengths of 60mm were investigated. One geometry had a phase of π/2, which was termed the “peak” configuration, while the other had a phase of 3π/2, which was termed the “trough” configuration. Surface flow visualisation, force measurements, and wake surveys were conducted on the wing configurations at a 225,000 chord Reynolds number. The flow visualisation was conducted at 0°, 3°, 6°, 9°, and 12° AOAs, the wake surveys were conducted at 0°, 3°, 6°, and 9° AOAs, and the force measurements were conducted from −2° to 15° AOAs in 1° increments. The wings were NACA 0021 profiles, untapered, and swept at a 35° angle. Evidence of the flow mechanism “compartmentalization” was observed over the trough configuration at 12° AOA. At 1° and 2° AOAs, the tubercle configurations typically reduced the lift coefficient and lift-to-drag ratio by 3%, but neither configuration greatly affected the drag coefficient. Neither tubercle configuration greatly affected the lift coefficient, drag coefficient, or lift-to-drag ratio from 3° to 15° AOAs, with typical changes of 1% or 2% observed. Both tubercle configurations typically changed the induced and profile drag coefficients by 2% and 5%, respectively, from 0° to 9° AOAs. From 6° to 9° AOAs, the π/2 and 3π/2 tubercle configurations typically changed the wingtip vortex strength by 2.2%, and had opposite effects from each other.