Passive shear layer regularization experiments in wind tunnels and feed-forward adaptive-optic correction

Donald J. Wittich, Daniel A. Duffin, Eric J. Jumper, Alan B. Cain, Edward J. Kerschen

Research output: Chapter in Book/Report/Conference proceedingConference contribution

8 Scopus citations

Abstract

Shear layer regularization is a fundamental requirement in a Feed-Forward, Adaptive-Optic (FFAO) wavefront correction scheme applied to a beam passing through the shear layer. 'Passive regularization' exploits the self-sustained oscillations of a shear layer over a resonant cavity, thereby eliminating the need for active flow control actuation. In wind tunnel tests, a strong acoustic resonance coupled with the cavity shear layer feedback mechanism produced a robust, predictable shear layer motion. The unsteady pressure at the upstream wall of the cavity was periodic enough to be used as a reliable phase reference. This phase reference was used to drive a phase-locked wavefront acquisition system and, ultimately, a deformable mirror which applied a feed-forward wavefront correction. The source of the strong acoustic resonance resulted from trapped duct modes, a result of the particular cavity and wind tunnel geometry combination. Unsteady pressure data indicated that this otherwise undesirable source of resonance can be mitigated by lining the wind tunnel wall opposite the cavity with an acoustically absorbent material.

Original languageEnglish (US)
Title of host publication47th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition
StatePublished - Dec 1 2009
Event47th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition - Orlando, FL, United States
Duration: Jan 5 2009Jan 8 2009

Publication series

Name47th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition

Other

Other47th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition
Country/TerritoryUnited States
CityOrlando, FL
Period1/5/091/8/09

ASJC Scopus subject areas

  • Space and Planetary Science
  • Aerospace Engineering

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