Array Processing of Porous Trailing Edge Aeroacoustics*

This presentation concerns characterization of the sound generated by a vortex ring passing near the edge of a non-compact porous plate, using a microphone array.  These measurements were performed to test theoretical predictions of how source sound power, waveform, and acoustic directivity all change with plate porosity.  The measurements were performed in the ARL Penn State anechoic chamber, for four plate porosities, and for vortex ring convection speeds ranging from 39 m/s to 86 m/s.  Vortex ring motion, including convection speed, was estimated from high-speed Schlieren imaging.  A circular 12 microphone array, centered on the edge, measured the far-field radiated sound, synchronously with the vortex ring motion video capture.  Using principal component analysis, dimensional reduction of the measured microphone signals was used to estimate the aeroacoustic source waveform, sound power scaling and directivity.