A Development and Assessment of Variable-Incidence Angle Vortex Generator at Low Reynolds Number of ~ 5×104

Abstract

The aerodynamic benefit for conventional vortex generator (VG) is often counterbalanced by the appearance of parasite drag. An immovable installation similar to a fixture also limited its application. To overcome those issues, this paper proposes a variable-incidence-angle vortex generator (VIVG). Counter-rotated miniature gears with a single rack-pinion system adjust the incidence angle of the VIVG, thereby precisely control mixing flux at boundary layer interface with minimizing the parasite drag. The variable incidence angle of the VIVG was then examined to evaluate the applicability of the VIVG at low Reynolds number. The VIVG was mounted on a NACA 0015 airfoil, and a low-turbulence blowing type wind tunnel was employed. We found that the VIVG effectively eliminated laminar separation bubbles, and suppressed separation at Reynolds number of 5.4 × 104; excessive lift production at low Reynolds number became similar to a theoretical value of potential flow (CL = 2πα). It was also found that the VIVG can reduce the drag in the pre-stall region at the low Re with small incidence angles, providing a noticeable increment of the lift-to-drag ratio. The large incidence angle of VIVG was also useful both to extend the stall point and to produce higher lift force with reasonable efficiency. These clearly indicate that the VIVG is applicable for performance improvement of aerodynamic devices operated in low Reynolds number flow fields.