Wing-tip flow separation control using localized steady suction*

Leading-edge slats are used for increasing wing performance for takeoff and landing. Due to complexity, the slat is not covering the full span of the wing, leaving the tip region “unprotected”. The flow on the unprotected region of the outer wing tends to separate from the surface, resulting in reduced lift and increased drag. A numerical and experimental study was performed on a 3D high-lift wing configuration, which consists of swept-back (by 25°) wing with trailing edge flap deflected at 20°, leading edge slat and rounded (in plan view) wing tip. Active flow control (AFC) in the form of localized steady suction was shown numerically to be significantly superior to steady blowing and was used experimentally to delay the wingtip stall, improving lift and reducing drag. It was shown that the performance degradation is due to adverse interaction between the slat edge, flap edge and wing tip vortices, that was eliminated using steady suction.