Owl-inspired leading-edge serrations play a crucial role in aerodynamic force production and sound suppression

Bioinspir Biomim. 2017 Jul 4;12(4):046008. doi: 10.1088/1748-3190/aa7013.

Abstract

Owls are widely known for silent flight, achieving remarkably low noise gliding and flapping flights owing to their unique wing morphologies, which are normally characterized by leading-edge serrations, trailing-edge fringes and velvet-like surfaces. How these morphological features affect aerodynamic force production and sound suppression or noise reduction, however, is still not well known. Here we address an integrated study of owl-inspired single feather wing models with and without leading-edge serrations by combining large-eddy simulations (LES) with particle-image velocimetry (PIV) and force measurements in a low-speed wind tunnel. With velocity and pressure spectra analysis, we demonstrate that leading-edge serrations can passively control the laminar-turbulent transition over the upper wing surface, i.e. the suction surface at all angles of attack (0° < AoA < 20°), and hence play a crucial role in aerodynamic force and sound production. We find that there exists a tradeoff between force production and sound suppression: serrated leading-edges reduce aerodynamic performance at lower AoAs < 15° compared to clean leading-edges but are capable of achieving both noise reduction and aerodynamic performance at higher AoAs > 15° where owl wings often reach in flight. Our results indicate that the owl-inspired leading-edge serrations may be a useful device for aero-acoustic control in biomimetic rotor designs for wind turbines, aircrafts, multi-rotor drones as well as other fluid machinery.

MeSH terms

  • Air
  • Animals
  • Biomechanical Phenomena
  • Biomimetic Materials*
  • Biomimetics
  • Equipment Design
  • Feathers / anatomy & histology*
  • Feathers / physiology*
  • Flight, Animal / physiology*
  • Models, Biological
  • Noise / prevention & control*
  • Strigiformes / anatomy & histology*
  • Strigiformes / physiology*
  • Wings, Animal / anatomy & histology*
  • Wings, Animal / physiology*