The origin of nearly-periodic velocity fluctuations over a delta
wing was investigated, and the results were used to modify these fluctuations.
Smoke streakline videography, surface hot-films and phase-resolved laser
velocimetry were used to quantify fluctuations and visualize structures
near the surface of the 59.3°-delta wing. The evolution of the
measured fluctuations over a cycle of periodicity showed the convection
of rotating structures. Small fences attached to the leeward
side of the model modified the fluctuations. Fence-off and -on lift,
drag and pitching moment measurements verified wing performance while autospectral
measurements quantified modification of the fluctuations. A fence
aligned parallel and inboard of the secondary vortex separation line displayed
the most overall attenuation with the least effects on aerodynamic characteristics.
Other fence alignments showed varying results including frequency shifts
and spectral amplification. These modifications further demonstrate
the origination and importance of fluctuations near the surface, as opposed
to the core of the vortex or the wing leading-edge.