Experimental study of the unsteady aerodynamics during flapping flight of birds: European Starling, Western Sandpiper and American Robin

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TypeArticle
Proceedings title10th Pacific Symposium on Flow Visualization and Image Processing, 15-18 June 2015, Naples, Italy: Proceedings
Conference10th Pacific Symposium on Flow Visualization and Image Processing, 15-18 June 2015, Naples, Italy
ISBN9788890648434
Article numberPSFVIP 10-111
Subjectbirds’ aerodynamics; high-speed PIV; wind tunnel; wakes
AbstractBirds’ unique characteristics such as wing shape, flexibility, feathers, flapping motion, etc., result in high aerodynamic performance. Using various flight modes such as gliding, bounding, and flapping, birds can use a single propulsion system for multiple functions. In low Reynolds number flyers using flapping flight mechanisms, the contribution of unsteady effects on lift and drag is not entirely understood. To gain insight about the unsteady contributions, a controlled study on the near wake flow behind freely flying birds was performed. Long duration, time resolved particle image velocimetry (PIV), combined with high speed imaging has been used to characterize the various flow features in the wake that are associated with flapping flight. The specially designed PIV system can sample the flow field for twenty minutes yielding a continuous measurement, sampling several wingbeat cycles consecutively. Time series of the vorticity fields have been expressed as composite wake plots, which reveal various characteristics of the wake during the upstroke (US) and down stroke (DS) phase of the flapping as well as the transition between US to DS and vice versa. Comparison between the near wake fields behind the three birds show remarkable similarity in their wake structure. We have identified over multiple wing beat cycles the presence of what appears to be an overlap of two distinct wakes during the transition from US toDS, named “double branch”. Over the region of the double branch, the majority of net positive circulation is accumulated. Indicating this may be a key feature in producing lift, and thus contribute to the observed high aerodynamic performance.
Publication date
PublisherfedOA
LanguageEnglish
AffiliationAerospace; National Research Council Canada
Peer reviewedYes
NPARC number23001926
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Record identifierc3e77e5f-0b06-47b9-8410-1b47f380c15f
Record created2017-06-01
Record modified2017-06-01
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