F. M. Payne, R. C. Nelson, and T. T. Ng
University of Notre Dame

The above photographs show the breakdown of a leading-edge vortex on an 85 swept delta wing at a 40 angle of attack. The freestream velocity is 10 ft/sec. For highly swept wings at high angles of attack, the vortices tend to break down asymmetrically. In Fig. 1, a column of smoke introduced upstream of the test section impinges on the apex of the model and is entrained into the vortices. The right vortex is breaking down at x/c=0.50. Figure 2 was obtained using the laser sheet technique. It is a multiple exposure showing five lateral cross sections of the flow field. The fourth cross section from the apex is cutting directly through the bubble region of the breakdown. Figure 3 is a longitudinal cross section of the vortices obtained by rotating the laser sheet by 90 . A region of high-speed axial flow occurs in the core of each vortex and appears in the photographs as an area void of smoke.

Figure 1

Figure 2

Figure 3