Attenuation of low-speed flow-induced cavity tones using plasma actuators

The aeroacoustic environment of an open cavity with a length-to-depth (L/D) ratio of 1.0 was studied with and without plasma actuators. The study was conducted through low-speed wind-tunnel experiments at freestream velocities between 10 and 20 m/s, corresponding to Reynolds numbers based on the depth of the cavity of 3.6 x 10(4) to 7.1 x 10(4). The fluid flow inside the cavity was studied using a range of measurement techniques, which include oil flow, particle imaging velocimetry, and surface-mounted-microphone measurements. For acoustic control, an array of 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 particle imaging velocimetry surveys around the electrode elements reveal vortical structures produced by the plasma actuators. These structures convect downstream with the mean flow and produce spanwise variations in the flow over the cavity that affect the spanwise coherence of the shear layer and hence the corresponding Rossiter mode.