Features of owl wings that promote silent flight.
Owls are an order of birds of prey that are known for the development of a silent flight. We review here the morphological adaptations of owls leading to silent flight and discuss also aerodynamic properties of owl wings. We start with early observations (until 2005), and then turn to recent advances. The large wings of these birds, resulting in low wing loading and a low aspect ratio, contribute to noise reduction by allowing slow flight. The serrations on the leading edge of the wing and the velvet-like surface have an effect on noise reduction and also lead to an improvement of aerodynamic performance. The fringes at the inner feather vanes reduce noise by gliding into the grooves at the lower wing surface that are formed by barb shafts. The fringed trailing edge of the wing has been shown to reduce trailing edge noise. These adaptations to silent flight have been an inspiration for biologists and engineers for the development of devices with reduced noise production. Today several biomimetic applications such as a serrated pantograph or a fringed ventilator are available. Finally, we discuss unresolved questions and possible future directions.
Institute of Zoology , RWTH Aachen University , Aachen , Germany.
Hermann
0000-0002-8191-7595
H
Wagner
Institute of Zoology , RWTH Aachen University , Aachen , Germany.
Matthias
M
Weger
Institute of Aerodynamics , RWTH Aachen University , Aachen , Germany.
Michael
M
Klaas
Institute of Aerodynamics , RWTH Aachen University , Aachen , Germany.
Wolfgang
W
Schröder
Reynolds number; feather; silent flight; trailing-edge noise; wing; wing load