Experimental analysis of the flow field over a novel owl based airfoil

Klän, Stephan; Bachmann, Thomas; Klaas, Michael; Wagner, Hermann; Schröder, Wolfgang

doi:10.1007/s00348-008-0600-7

Cited by 62 publications

(55 citation statements)

References 18 publications

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“…In contrast with other results [47][48][49], no change in aerodynamic performance was observed by these authors. Furthermore, at high angles of attack (248), Geyer et al [51] observed a reduction of 5 dB in gliding-flight noise in one of two barn owl wings tested.…”

Section: Serrationscontrasting

confidence: 55%

“…Klän et al [47,48] and Winzen et al [49] have studied the effect of serrations on the aerodynamic behaviour of model and natural owl wings. These authors fitted a wing model with a geometry reflecting the wing shape of a barn owl with different types of serrations, e.g.…”

Section: Serrationsmentioning

confidence: 99%

“…We turn to the latter issue in the next section. Klän et al [47,58] and Winzen et al [59,60] conducted experiments with several artificial velvet-like surfaces that mimicked the length and the density of the natural pennula (figure 6a). The softness of the artificial material was also chosen to be similar to that of the natural owl-wing surface.…”

Section: Serrationsmentioning

confidence: 99%

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Features of owl wings that promote silent flight

et al. 2017

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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.

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Section: Serrationscontrasting

confidence: 55%

Section: Serrationsmentioning

confidence: 99%

Section: Serrationsmentioning

confidence: 99%

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Features of owl wings that promote silent flight

et al. 2017

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“…However, the air flow tends to separate at highly cambered wing geometries. Klän et al 28 performed wind tunnel experiments with wing geometries inspired by barn owl wings. These authors found a relative huge air-flow separation at the upper wing surface at Reynolds numbers of 20,000 -60,000 at a wing with a clean surface.…”

Section: Are Barn Owl Wings Adapted To Low-speed Flight?mentioning

confidence: 99%

The barn owl wing: an inspiration for silent flight in the aviation industry?

2011

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Barn owls are specialists in prey detection using acoustic information. The flight apparatus of this bird of prey is most efficiently adapted to the hunting behavior by reducing flight noise. An understanding of the underlying mechanisms owls make use of could help minimize the noise disturbances in airport or wind power plant neighborhood. Here, we characterize wings of barn owls in terms of an airfoil as a role model for studying silent flight. This characterization includes surface and edge specialization (serrations, fringes) evolved by the owl. Furthermore, we point towards possible adaptations of either noise suppression or air flow control that might be an inspiration for the construction of modern aircraft. Three-dimensional imaging techniques such as surface digitizing, computed tomography and confocal laser scanning microscopy were used to investigate the wings and feathers in high spatial resolution. We show that wings of barn owls are huge in relation to their body mass resulting in a very low wing loading which in turn enables a slow flight and an increased maneuverability. Profiles of the wing are highly cambered and anteriorly thickened, especially at the proximal wing, leading to high lift production during flight. However, wind tunnel experiments showed that the air flow tends to separate at such wing configurations, especially at low-speed flight. Barn owls compensated this problem by evolving surface and edge modifications that stabilize the air flow. A quantitative three-dimensionally characterization of some of these structures is presented.

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“…Noise was effectively mitigated due to the edge interaction with turbulent eddies in the boundary layer passing over owl's wing feathers. 13 As a result, bionic designs of foliated structures such as fans, airfoils 11,14 and gliders 1, 15 have been motivated a lot by the owl feather outline edges in acoustic stealth.…”

Section: Introductionmentioning

confidence: 99%