BIO-INSPIRED TRAILING EDGE NOISE CONTROL
William Devenport, Virginia Tech
August 7, 2015, 1:00 pm, NASA Langley, Bldg 2102, Rm 114/115
Strategies for trailing edge noise control have been inspired by the downy canopy that covers the surface of exposed flight feathers of many owl species. Previous wind tunnel measurements have shown that canopies of similar characteristics can reduce surface pressure fluctuations on the underlying surface by as much as 30dB, and significantly attenuate roughness noise generated by that surface. In the present work, surface treatments have been designed to replicate the effects of the canopy in a form suitable for application to an airfoil. The treatments were installed directly upstream of the trailing edge to modify the boundary layer turbulence prior to acoustic scattering by the edge. Over 20 variants of these designs have been tested by performing aeroacoustic wind tunnel measurements on a tripped DU96-W180 airfoil at chord Reynolds numbers up to 3 million. Compared to the unmodified airfoil, the treatments were found to be effective, providing up to 10dB of broadband attenuation of trailing edge noise. The treatment remains effective throughout a wide parameter range and is not highly dependent on a particular geometry, but there appears to be strong potential for optimization. Treatments were found to be effective over an angle of attack range that extends over 9 degrees from zero lift. Aerodynamic impact of the treatment appears minimal.
Prof. William Devenport leads the Center for Renewable Energy and Aerodynamic Testing at Virginia Tech. He is also Director of the Virginia Tech Stability Wind Tunnel. He heads an active group of researchers dedicated to the study of aerodynamics and aeroacoustics. The group currently tackling a wide range of problems including sound generation in rotors in inhomogeneous flows, rough wall boundary layer pressure fluctuations at high Reynolds numbers, trailing edge noise control, the aeroacoustic testing of wind turbine blades, and the study and development of aeroacoustic wind tunnel testing techniques and instrumentation. Many of these efforts are centered on the Virginia Tech Stability Wind Tunnel and its novel Kevlar-walled aeroacoustic test section system.