AIAA Paper 97-0548, 35th Aerospace Sciences Meeting
Reduction of Fluctuations over Swept Wings Using Mini-Fences
M. A. Klein, W. K. Lentz and N. M. Komerath
ABSTRACT Passive and active surface devices are used to modify the narrow-band
velocity fluctuations over a 59.3 degree delta wing at high angles of attack.
Previous work has traced these fluctuations to counter-rotating structures
in the shear layer below the post-burst vortex. Small vertical fences placed
near the point of origin of the fluctuations attenuate the peak spectral
energy by as much as 78%. The lift and drag are shown to be unaffected. Fences
placed at other locations and orientations show various levels of suppression
and amplification. The most effective fence height, position, and orientation
for attenuation at 25 deg. angle of attack are identified. An active fence
and a ramp modulated at the fluctuation frequency show attenuation corresponding
to the effective duty cycle of deployment in a given range of the shear layer.
It is seen that the fences must extend well beyond the surface boundary layer
to be effective, but extending into the central region of the flow is ineffective,
further proving that the fluctuations originate in the outer shear layer
of the vortex, not in the core.
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