Aerodynamics of finite wings with leading-edge flags

Post-stall lift enhancement on rectangular and tapered wing planforms by means of attached leading-edge flags has been investigated at a Reynolds number of 100,000. The study has aimed to investigate the fluid-flag interactions in the presence of a wing tip and variable chord-length, and also compares the results with those for the two-dimensional airfoil case. For the rectangular wing, the characteristics of the interaction of the wake, flag, and vortex as well as the frequency of flag oscillations reveal no noticeable differences from those of the nominally two-dimensional airfoil. For the aspect ratio tested, this suggests that the wake three-dimensionality does not have much effect. However, the magnitude of the lift enhancement is lower due to the existence of the tip vortex. For both the airfoil and rectangular wing, the flag oscillations are nearly twodimensional and occur in the first beam mode. For the tapered wing tested (with the taper ratio of 0.33 and semi-aspect ratio of 4), the frequency of the flag oscillations and the lift enhancement are almost identical to those of the rectangular wing. However, there is a significant phase lag of the flag oscillations towards the wing tip for the tapered wing. Phase-averaged velocity measurements suggest oblique vortex shedding from the flag.