Bat Flight Generates Complex Aerodynamic Tracks

The flapping flight of animals generates an aerodynamic footprint as a time-varying vortex wake in which the rate of momentum change represents the aerodynamic force. We showed that the wakes of a small bat species differ from those of birds in some important respects. In our bats, each wing generated its own vortex loop. Also, at moderate and high flight speeds, the circulation on the outer (hand) wing and the arm wing differed in sign during the upstroke, resulting in negative lift on the hand wing and positive lift on the arm wing. Our interpretations of the unsteady aerodynamic performance and function of membranous-winged, flapping flight should change modeling strategies for the study of equivalent natural and engineered flying devices.

[1]  O. Tietjens,et al.  Applied hydro- and aeromechanics , 1934 .

[2]  O. Tietjens,et al.  Fundamentals of hydro- and aeromechanics , 1934 .

[3]  U. M. Norberg,et al.  Aerodynamics of hovering flight in the long-eared bat Plecotus auritus. , 1976, The Journal of experimental biology.

[4]  U. M. Norberg,et al.  Aerodynamics, kinematics, and energetics of horizontal flapping flight in the long-eared bat Plecotus auritus. , 1976, The Journal of experimental biology.

[5]  N. V. KOKSHAYSKY,et al.  Tracing the wake of a flying bird , 1979, Nature.

[6]  Jmv Rayner,et al.  Momentum and energy in the wake of a pigeon (Columba livia) in slow flight , 1984 .

[7]  H. Aldridge,et al.  Kinematics and aerodynamics of the greater horseshoe bat, Rhinolophus ferrumequinum, in horizontal flight at various flight speeds. , 1986, The Journal of experimental biology.

[8]  Geoffrey Spedding,et al.  The wake of a jackdaw (Corvus monedula) in slow flight , 1986 .

[9]  Adrian L. R. Thomas,et al.  Vortex flow visualizations reveal change in upstroke function with flight speed in bats , 1986, Nature.

[10]  H. Aldridge,et al.  Body accelerations during the wingbeat in six bat species: the function of the upstroke in thrust generation , 1987 .

[11]  G. Spedding.  The Wake of a Kestrel (Falco Tinnunculus) in Flapping Flight , 1987 .

[12]  William R. Walsh,et al.  Mechanical properties of bat wing membrane skin , 1996 .

[13]  E. Laitone.  Wind tunnel tests of wings at Reynolds numbers below 70 000 , 1997 .

[14]  Y. Winter.  Flight speed and body mass of nectar-feeding bats (Glossophaginae) during foraging. , 1999, The Journal of experimental biology.

[15]  A Hedenström,et al.  A family of vortex wakes generated by a thrush nightingale in free flight in a wind tunnel over its entire natural range of flight speeds , 2003, Journal of Experimental Biology.

[16]  Adrian L. R. Thomas,et al.  Flying and swimming animals cruise at a Strouhal number tuned for high power efficiency , 2003, Nature.

[17]  B. Tobalske,et al.  Aerodynamics of the hovering hummingbird , 2005, Nature.

[18]  A Hedenström,et al.  Vortex wakes generated by robins Erithacus rubecula during free flight in a wind tunnel , 2006, Journal of The Royal Society Interface.

[19]  Wei Shyy,et al.  Numerical Simulations of Membrane Wing Aerodynamics for Micro Air Vehicle Applications , 2005 .

[20]  York Winter,et al.  Wing beat kinematics of a nectar-feeding bat, Glossophaga soricina, flying at different flight speeds and Strouhal numbers , 2006, Journal of Experimental Biology.

[21]  A. Hedenström,et al.  Wake structure and wingbeat kinematics of a house-martin Delichon urbica , 2007, Journal of The Royal Society Interface.