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Time-resolved vortex wake of a common swift flying over a range of flight speeds.

Henningsson, Per LU ; Muijres, Florian LU and Hedenström, Anders LU (2011) In Journal of the Royal Society Interface 8. p.807-816
Abstract
The wake of a freely flying common swift (Apus apus L.) is examined in a wind tunnel at three different flight speeds, 5.7, 7.7 and 9.9 m s(-1). The wake of the bird is visualized using high-speed stereo digital particle image velocimetry (DPIV). Wake images are recorded in the transverse plane, perpendicular to the airflow. The wake of a swift has been studied previously using DPIV and recording wake images in the longitudinal plane, parallel to the airflow. The high-speed DPIV system allows for time-resolved wake sampling and the result shows features that were not discovered in the previous study, but there was approximately a 40 per cent vertical force deficit. As the earlier study also revealed, a pair of wingtip vortices are trailing... (More)
The wake of a freely flying common swift (Apus apus L.) is examined in a wind tunnel at three different flight speeds, 5.7, 7.7 and 9.9 m s(-1). The wake of the bird is visualized using high-speed stereo digital particle image velocimetry (DPIV). Wake images are recorded in the transverse plane, perpendicular to the airflow. The wake of a swift has been studied previously using DPIV and recording wake images in the longitudinal plane, parallel to the airflow. The high-speed DPIV system allows for time-resolved wake sampling and the result shows features that were not discovered in the previous study, but there was approximately a 40 per cent vertical force deficit. As the earlier study also revealed, a pair of wingtip vortices are trailing behind the wingtips, but in addition, a pair of tail vortices and a pair of 'wing root vortices' are found that appear to originate from the wing/body junction. The existence of wing root vortices suggests that the two wings are not acting as a single wing, but are to some extent aerodynamically detached from each other. It is proposed that this is due to the body disrupting the lift distribution over the wing by generating less lift than the wings. (Less)
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organization
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type
Contribution to journal
publication status
published
subject
in
Journal of the Royal Society Interface
volume
8
pages
807 - 816
publisher
Royal Society
external identifiers
  • wos:000289672200005
  • scopus:79955708251
ISSN
1742-5662
DOI
10.1098/rsif.2010.0533
language
English
LU publication?
yes
id
7e0decd5-7fee-4c53-829d-3b19cdfc9882 (old id 1756738)
date added to LUP
2010-12-30 11:16:34
date last changed
2017-10-22 03:17:38
@article{7e0decd5-7fee-4c53-829d-3b19cdfc9882,
  abstract     = {The wake of a freely flying common swift (Apus apus L.) is examined in a wind tunnel at three different flight speeds, 5.7, 7.7 and 9.9 m s(-1). The wake of the bird is visualized using high-speed stereo digital particle image velocimetry (DPIV). Wake images are recorded in the transverse plane, perpendicular to the airflow. The wake of a swift has been studied previously using DPIV and recording wake images in the longitudinal plane, parallel to the airflow. The high-speed DPIV system allows for time-resolved wake sampling and the result shows features that were not discovered in the previous study, but there was approximately a 40 per cent vertical force deficit. As the earlier study also revealed, a pair of wingtip vortices are trailing behind the wingtips, but in addition, a pair of tail vortices and a pair of 'wing root vortices' are found that appear to originate from the wing/body junction. The existence of wing root vortices suggests that the two wings are not acting as a single wing, but are to some extent aerodynamically detached from each other. It is proposed that this is due to the body disrupting the lift distribution over the wing by generating less lift than the wings.},
  author       = {Henningsson, Per and Muijres, Florian and Hedenström, Anders},
  issn         = {1742-5662},
  language     = {eng},
  pages        = {807--816},
  publisher    = {Royal Society},
  series       = {Journal of the Royal Society Interface},
  title        = {Time-resolved vortex wake of a common swift flying over a range of flight speeds.},
  url          = {http://dx.doi.org/10.1098/rsif.2010.0533},
  volume       = {8},
  year         = {2011},
}