Silent Owl Wings and Their Implications For Noise Reduction Technologies
From antiquity to Harry Potter, owls continue to captivate and mystify us. Perhaps owls’ most mysterious feat is their ability to fly silently, which enables them to both sneak up on prey and hunt on the wing using their ears alone. For over 80 years, silent owl flight has been linked to a set of unique plumage features, but only recently have the mechanisms to suppress the ‘swoosh’ noise from owl wings been addressed in earnest. This lecture will survey recent collaborative research into how the structure of these plumage features affects the boundary-layer flow over the wing and disrupts the generation of aerodynamic noise, and how this research may inform owl-inspired noise reduction technologies. To this end, aeroacoustic wind tunnel measurements of a biologically-inspired and installable device termed ‘finlets’ designed to mitigate edge noise will be presented. The finlet invention is demonstrated to achieve up to 10 dB of broadband attenuation of trailing-edge noise for a full-chord wind turbine airfoil and has been shown to remain effective over a broad range of angles of attack, with minimal impact on the aerodynamics. These features suggest a much broader industrial impact of owl-inspired noise reduction technology on future aeronautical, automotive, nautical, and wind energy designs.