Nature-inspired porous airfoils for sound reduction

Abstract

Inspired by the results from acoustic measurements on flying owls and prepared owl wings that support the thesis of the silent flight of owls, measurements were conducted on technical airfoils made from open-porous, flow-permeable materials, characterized by their air flow resistivity, in an aeroacoustic wind tunnel. One major objective of these experiments is the identification of porous materials that enable a reduction of aeroacoustic noise. Both the generation of trailing edge noise and the generation of leading edge noise were investigated using microphone array technology and three-dimensional deconvolution beamforming algorithms. The highest trailing edge noise reduction per unit lift force can be achieved by using airfoils with medium to high air flow resistivities, while the highest leading edge noise reduction was measured for airfoils with low air flow resistivities. © 2012 Springer Berlin Heidelberg.