G. D. Miller and C. H. K. Williamson
Cornell University

A great many studies have been directed towards understanding the flow over wings and, in particular, over a delta wing. Very surprisingly indeed, in our view, there exist no visualizations, from the laboratory, of the far-field development of the trailing vortex pair as it travels downstream, to our knowledge. Our flow visualization, involving novel free-flight gliding of a delta wing in water, shows for the first time, the exquisitely beautiful structure of the turbulent wake, in plan view (Fig. 1) and in side view (Fig. 2). One should note that these photographs are all to closely the same scale! The fluorescence dye, illuminated by a laser, shows that the near wake comprises an interaction between the primary streamwise vortex pair with the braid wake vortices between the pair. ^{[1] , [2]} Far downstream (64 chordlengths behind the wing) the primary vortex pair have reconnected and become large-scale rings (Fig. 3), although with a distinctly smaller length scale than predicted from Crow s analysis. ^[3]

Figure 1

Figure 2

Figure 3

This work is supported by the Office of Naval Research.