The near-surface flow structure and topologyon a delta wing of low sweep angle, having sinusoidalleading edges of varying amplitude and wavelength, areinvestigated using a stereoscopic technique of high-image-density particle image velocimetry at a Reynolds numberof 15,000. Identification of critical points, in conjunctionwith surface-normal vorticity and velocity, provides a basisfor determining the effectiveness of a given leading edge.At high angle of attack, where large-scale three-dimen-sional separation occurs from the wing with a straightleading edge, an amplitude of the leading-edge protuber-ance as small as one-half of one percent of the chord of thewing can substantially alter the near-surface topology.When the amplitude reaches a value of four percent of thechord, it is possible to completely eradicate the negativefocus of large-scale, three-dimensional separation, in favorof a positive focus of attachment. Moreover, alteration ofthe near-surface topology is most effective when the ratioof the wavelength to amplitude of the sinusoidal leadingedge is maintained at a small value.
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