The attenuation of cavity tones using plasma actuators

Chan, S., Zhang, X. and Gabriel, S. (1970) The attenuation of cavity tones using plasma actuators. 11th AIAA/CEAS Aeroacoustics Conference (26th AIAA Aeroacoustics Conference), Monterey, California. 22 - 24 May 2005. 14 pp .

Abstract

The aeroacoustic environment of an open cavity with length-depth (L/D) ratios of 0.5 and 1.0 was studied with and without plasma actuators. The study was conducted through low speed wind tunnel experiments at free stream velocities between 10m/s and 20m/s corresponding to Reynolds numbers, based on the depth of thecavity, of 2.7×10⁴ to 6.7×10⁴. The oncoming boundary layer was turbulent with a thickness typically of 0.1D. The fluid flow inside the cavities was studied using a range of measurement techniques. These include oil flow, particle imaging velocimetry (PIV) and surface mounted microphone measurements. For acoustic control an array of paraelectric plasma actuators were located on the approaching surface to the cavity, aligned with the direction of the oncoming flow. Results show that the plasma actuators lead to a significant attenuation of the dominant cavity mode. The PIV surveys around the electrode elements reveal vortical structures produced by the plasma actuators. It is surmised that these structures are convected downstream with the mean flow and produce disturbances similar to that of vortex generators. This affects the convection of discrete vortices in the cavity shear layer, disrupting the mechanisms that allow the cavity to produce tones. Results also show that for any given geometry and input voltage to the plasma actuator the attenuation in the dominant mode reduces with increasing flow speed.

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