Trailing-edge bluntness vortex shedding noise attenuation using perforated flat plates

The reduction of trailing-edge (TE) bluntness noise from a flat plate with a 3 mm thickness is investigated experimentally using perforations along the chord, as inspired by the porous trailing edges of owl wings. Edge porosity has been shown to reduce flow noise in experimental and theoretical works, where in the latter a single dimensionless parameter is shown to control the scaling of noise generation due to a vortical or turbulence source. This insight is applied to the analysis of the broadband noise produced by a boundary layer over a porous plate. An open jet wind tunnel gathers acoustic and flow measurements of flat plates with blunt TEs and different perforation designs. Sounds maps are generated using microphone array data and hot-wire testing investigates the specific flow behavior. Periodic vortex shedding occurs at the TE due to edge bluntness and creates tonal sound peaks that decrease in magnitude with increasing number of perforations. The presence of perforations also drastically increase roughness-induced noise, and the mechanisms behind this noise and associated vortex shedding at the TE are investigated by interrogating the velocity field with hot-wire probes.