Reductions Over all Angles

For all the angles of attack tested, surface fences are effective in reducing the spectral peak intensity.  At the reported maximum tail buffet angle of attack, 22°, over 60% reduction in peak spectral intensity is achieved.  Effectiveness is approximately linearly decreasing with angle of attack, with the exception of at 24° and 26°.  This sharp decrease in effectiveness at these angles is due to a change in the spectral characteristics.  Examining the spectra at these angles, the dominant peak nature is seen to be reduced and a dramatic rise in broad-band turbulence occurs.  At 28°, the peak nature returns to the spectra.  Surface fences are seen to be primarily effective at reducing the peak nature to the spectra and less effective at reducing the broad-band turbulence.

 

 
 
 
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:
Home: