technical paper
Trailing-edge fringes enable robust aeroacoustic performance in owl flight: a computational study
keywords:
aeroacoustics
trailing-edge fringes
owl
Trailing-edge (TE) fringes observed on owl wings are believed to play a crucial role in the silent flight of owls. The effects of TE fringes and underlying mechanisms on the aeroacoustic performance of owl wings, featured by curved leading edges, wavy TEs, and several feather slots at the wingtips, have not yet been addressed in association with real owl wings. In this study we for the first time constructed two 3D owl wing models, one with TE fringes and one without, based on real owl wing characteristics. Using large-eddy simulations and the Ffowcs Williams‒Hawkings analogy, the aeroacoustic characteristics of the wing models were analyzed. The results revealed that TE fringes effectively reduce aerodynamic noise without compromising aerodynamic performance. The study visualized the near-field flow dynamics, including nearfield flow and vortex structures, and flow fluctuations, demonstrating that the TE fringes break up large TE vortices, thereby suppressing TE flow fluctuations. Additionally, the fringes are observed to mitigate feather-slot interaction, effectively suppressing wingtip vortices. These combined mechanisms enhance the effectiveness of TE fringes in terms of aerodynamic force production and noise suppression. The findings contribute to understanding the role of TE fringes in silent owl flight and suggest the validity and feasibility of employing owl-inspired TE fringes in low-noise fluid machinery applications.