Effects of flexible owl-inspired serrations on aerodynamic performance and noise reduction

Abstract

Owls are a master to achieve silent flight in stealthy hunting or prey detection owing to their featured wing morphologies of leading-edge serrations, trail-edge fringes, and velvet-like surfaces. While the aeroacoustic characteristics of the owl-inspired leading-edge serrations has been a hot topic in terms of aerodynamic performance and noise suppression, their effects of serration-flexibility and passive deformation remain yet poorly studied. We have recently investigated experimentally the aerodynamic and acoustic performance of the propeller blades with both flexible and rigid serration-like appendages attached onto the blade tip. We utilized a high-speed camera system to measure the dynamic deformations of the serration-like structures and examined the aeroacoustic features of the various blades. Using three propeller blade models with the leading-edge (LE) serrations, we found that the flexible LE-serrated blade displays an optimal aeroacoustic performance with the high-frequency broadband noise suppressed remarkedly. Our results indicate that the flexible serrations with appropriate stiffness enable a pronounced sound reduction at high frequencies while sustaining the aerodynamic performance comparable to that of the non-serrated blades.