Estimation of unsteady aerodynamics in the wake of a freely flying european starling (Sturnus vulgaris)

Hadar Ben-Gida, Adam Kirchhefer, Zachary J. Taylor, Wayne Bezner-Kerr, Christopher G. Guglielmo, Gregory A. Kopp, Roi Gurka

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


Wing flapping is one of the most widespread propulsion methods found in nature; however, the current understanding of the aerodynamics in bird wakes is incomplete. The role of the unsteady motion in the flow and its contribution to the aerodynamics is still an open question. In the current study, the wake of a freely flying European starling has been investigated using long-duration high-speed Particle Image Velocimetry (PIV) in the near wake. Kinematic analysis of the wings and body of the bird has been performed using additional high-speed cameras that recorded the bird movement simultaneously with the PIV measurements. The wake evolution of four complete wingbeats has been characterized through reconstruction of the time-resolved data, and the aerodynamics in the wake have been analyzed in terms of the streamwise forces acting on the bird. The profile drag from classical aerodynamics was found to be positive during most of the wingbeat cycle, yet kinematic images show that the bird does not decelerate. It is shown that unsteady aerodynamics are necessary to satisfy the drag/thrust balance by approximating the unsteady drag term. These findings may shed light on the flight efficiency of birds by providing a partial answer to how they minimize drag during flapping flight.

Original languageEnglish
Article numbere80086
JournalPLoS ONE
Issue number11
StatePublished - 22 Nov 2013

ASJC Scopus subject areas

  • General Biochemistry, Genetics and Molecular Biology
  • General Agricultural and Biological Sciences
  • General


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