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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