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PLoS One. 2014 Feb 5;9(2):e86506. doi: 10.1371/journal.pone.0086506. eCollection 2014.

Diving-flight aerodynamics of a peregrine falcon (Falco peregrinus).

Author information

1
Institute of Mechanics and Fluid Dynamics, TU Bergakademie Freiberg, Freiberg, Germany.
2
Institute of Zoology, Rheinische Friedrich-Wilhelms Universität Bonn, Bonn, Germany.
3
Clinic for Birds, Reptiles, Amphibians, and Fish, Justus-Liebig-Universität Giessen, Giessen, Germany.

Abstract

This study investigates the aerodynamics of the falcon Falco peregrinus while diving. During a dive peregrines can reach velocities of more than 320 km h⁻¹. Unfortunately, in freely roaming falcons, these high velocities prohibit a precise determination of flight parameters such as velocity and acceleration as well as body shape and wing contour. Therefore, individual F. peregrinus were trained to dive in front of a vertical dam with a height of 60 m. The presence of a well-defined background allowed us to reconstruct the flight path and the body shape of the falcon during certain flight phases. Flight trajectories were obtained with a stereo high-speed camera system. In addition, body images of the falcon were taken from two perspectives with a high-resolution digital camera. The dam allowed us to match the high-resolution images obtained from the digital camera with the corresponding images taken with the high-speed cameras. Using these data we built a life-size model of F. peregrinus and used it to measure the drag and lift forces in a wind-tunnel. We compared these forces acting on the model with the data obtained from the 3-D flight path trajectory of the diving F. peregrinus. Visualizations of the flow in the wind-tunnel uncovered details of the flow structure around the falcon's body, which suggests local regions with separation of flow. High-resolution pictures of the diving peregrine indicate that feathers pop-up in the equivalent regions, where flow separation in the model falcon occurred.

PMID:
24505258
PMCID:
PMC3914994
DOI:
10.1371/journal.pone.0086506
[Indexed for MEDLINE]
Free PMC Article

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