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The relationship between wingbeat kinematics and vortex wake of a thrush nightingale

Författare

Summary, in English

The wingbeat kinematics of a thrush nightingale Luscinia luscinia were measured for steady flight in a wind tunnel over a range of flight speeds (5-10 m s(-1)), and the results are interpreted and discussed in the context of a detailed, previously published, wake analysis of the same bird. Neither the wingbeat frequency nor wingbeat amplitude change significantly over the investigated speed range and consequently dimensionless measures that compare timescales of flapping vs. timescales due to the mean flow vary in direct proportion to the mean flow itself, with no constant or slowly varying intervals. The only significant kinematic variations come from changes in the upstroke timing (downstroke fraction) and the upstroke wing folding (span ratio), consistent with the gradual variations, primarily in the upstroke wake, previously reported. The relationship between measured wake geometry and wingbeat kinematics can be qualitatively explained by presumed self-induced convection and deformation of the wake between its initial formation and later measurement, and varies in a predictable way with flight speed. Although coarse details of the wake geometry accord well with the kinematic measurements, there is no simple explanation based on these observed kinematics alone that accounts for the measured asymmetries of circulation magnitude in starting and stopping vortex structures. More complex interactions between the wake and wings and/or body are implied.

Publiceringsår

2004

Språk

Engelska

Sidor

4255-4268

Publikation/Tidskrift/Serie

Journal of Experimental Biology

Volym

207

Issue

24

Dokumenttyp

Artikel i tidskrift

Förlag

The Company of Biologists Ltd

Ämne

  • Biological Sciences

Status

Published

Forskningsgrupp

  • Animal Flight Lab

ISBN/ISSN/Övrigt

  • ISSN: 1477-9145