Experimental investigation of the self-induction theory of vortex breakdown and new observations in the transient development of a delta wing leading edge vortex

The transient development of the leading edge vortex of a 65-deg sweep delta wing is investigated in water tunnel experiments using flow visualization and particle image velocimetry (PIV) measurements. The experiments were conducted at root chord Reynolds numbers from 0 to 3x10 4. The transient results provide experimental evidence supporting the self-induction theory of vortex breakdown. A core radius based circulation overshoot is discovered and attributed to transient development of the vortex core. The transient leading edge vortex core development indicates an initial conical vortex core along the axial direction that transitions to a cylindrical axial core. A passive device that asymmetrically extends the vortex breakdown location is discovered and the mechanisms describing the extension are proposed.