Propeller Noise in Ground Effect with Perforated Sheets

This study experimentally investigates the aeroacoustic performance of propellers operating in ground effect with both solid and perforated ground planes. The experiments were conducted in an anechoic chamber, using a 12''x6'' propeller configured in a pusher arrangement. Initially, a rigid instrumented flat plate was used as the ground plane at varying distances from the propeller. Subsequently, the rigid ground plane was replaced with perforated sheets characterized by different perforation parameters. Noise data were captured using a polar array of microphones positioned in both near-field and far-field regions. The results demonstrate that perforated sheet ground planes significantly enhance noise suppression across most observer angles compared to solid ground planes. It was also found that increasing the perforation of the sheets leads to an overall decrease in sound pressure levels. Furthermore, the sound pressure spectra reveal that noise reduction occurs in both low and high frequency content, depending on the observer angle. These findings hold significant potential for designing quieter and more efficient Urban Air Mobility vehicles, thereby supporting their seamless integration into urban environments.