Since 1976 Richard T. Whitcomb has shown that the efficiency of the aircraft equipped with winglet is better than other devices set at the wing tip, winglets are now incorporated into most new commercial and military transport jets. In this paper, the geometry of the wing is of Gulfstream IV, and its airfoil is chosen as Whitcomb’s supercritical airfoil. The three different configurations are the bare wing of no wing tip device, the wing tip equipped with spiroid winglet, and blowing on the spiroid winglet. The goal of blowing at the wing tip is to advance the customary time of decaying trailing vortices and to reduce the strength of trailing vortices. Consider the spiroid winglet and blowing at wing tip coupled together, and we could find a suitable result that reduced the total drag as well as the strength of the trailing vortex, thus the flight could become more efficient.
Journal of Aeronautics, Astronautics and Aviation. Series A 41(1), pp.23-29