F-15 Surface Fences

Previous research at Georgia Tech showed that instability driven vortical structures develop in the vortex/surface interaction region on swept wing at angle of attack.  These structures are thought lift off the surface, spiral around the primary vortex and cause the nearly periodic velocity fluctuations seen at the tails.  Tracing these fluctuations to their approximate origin at the wing surface, shows a region where the low energy structures may be easily disrupted.  Experiments using small surface fences show up to a 67% reduction in spectral peak intensity at the tails.  Also, spectral amplification is seen at further downstream locations.  Further tests were performed to verify fence effectiveness with change in angle of attack.

 F-15 Tail Buffet Alleviation Results
Introduction:    Spectral Amplification:    Centrifugal Instabilities:
Reduced Frequency Scaling:    Linear Peak Frequency/Velocity Slopes:    Models Tested:
Empirical Peak Frequency Data:    Surface Fence Tests:    Reduction in Spectral Intensity:
Reductions Over all Angles:    Comparison with Flight Tests:    Summary:
Future F-15 Wind Tunnel Tests: