Small Leading-Edge Flap for Flow Control on a 45-Deg Delta Wing

The characteristics of rolling moment in a 45-deg delta wing with a leading-edge flap were studied to examine its effects in pre- and post-stall regimes, where conventional control surfaces are ineffective. A small flap with a height of 2mm was employed to control the flow, which was placed on the round leading-edge of the delta wing from 10 to 75% chord. Wind-tunnel experiments were carried out for static aerodynamic force measurements and flow visualization. In the pre-stall regime, it is observed that the single flap can produce about ±0.01 of rolling moment coefficient, which is sufficient for flight control. On the other hand, in the post-stall regime, its rolling moment characteristics are quite nonlinear and complex. The flap can basically reduce the unsteady moment by interfering with the development of a leading-edge vortex, or promoting the flow attachment to the wing surface.