Abstract
We present synchronized time-resolved measurements of the wing kinematics and wake velocities for a medium sized bat, Cynopterus brachyotis, flying at low-medium speed in a closed-return wind tunnel. Measurements of the motion of the body and wing joints, as well as the resultant wake velocities in the Trefftz plane are recorded at 200 Hz (approximately 28–31 measurements per wing beat). Circulation profiles are found to be quite repeatable although variations in the flight profile are visible in the wake vortex structures. The circulation has almost constant strength over the middle half of the wing beat (defined according the vertical motion of the wrist, beginning with the downstroke). A strong streamwise vortex is observed to be shed from the wingtip, growing in strength during the downstroke, and persisting during much of the upstroke. At relatively low flight speeds (4.3 m/s), a closed vortex structure behind the bat is postulated.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Abdel-Aziz YI, Karara HM (1971) Direct linear transformation from comparator coordinates into object space coordinates in close-range photogrammetry. In: Proceedings of the symposium on close-range photogrammetry, American Society of Photogrammetry, Falls Church, pp 1–18
Adrian RJ, Christensen KT, Liu ZC (2000) Analysis and interpretation of instantaneous turbulent velocity fields. Exp Fluids 29:275–290
Betz A (1932) Verhalten von Wirbelsystemen. Zeitschrift fur angewandte Mathematikund Mechanik 12:164–174 (Also published as NACA TM 713)
Devenport WJ, Rife MC, Liapis SI, Follin GJ (1996) The structure and development of a wing-tip vortex. J Fluid Mech 312:67–106
Ellington CP (1999) The novel aerodynamics of insect flight: applications to micro-air vehicles. J Exp Biol 202:3439–3448
Ellington CP, van den Berg C, Willmott AP, Thomas ALR (1996) Leading-edge vortices in insect flight. Nature 384:626–630
Gerontakos P, Lee T (2006) Near-field tip vortex behind a swept wing model. Exp Fluids 40:141–155
Hedenström A, Johansson LC, Wolf M, von Busse R, Winter Y, Spedding GR (2007) Bat flight generates complex aerodynamic tracks. Science 316:894–897
Hedenström A, Rosén M, Spedding GR (2006) Vortex wakes generated by robins Erithacus rubecula during free flight in a wind tunnel. J Royal Soc Interface 3:263–276
Iriarte-Diaz J, Riskin DK, Willis DJ, Breuer KS, Swartz SM (2009a) No net thrust on the upstroke: whole-body kinematics of a fruit bat reveal the influence of wing inertia on body accelerations (in review)
Iriarte-Diaz J, Riskin DK, Swartz SM (2009b) Modulation of wingbeat kinematics with flight speed in the fruit bat Cynopterus brachyotis (in prep.)
Lilienthal O (1889) Der Vogelflug als Grundlage der. Fliegekunst Leipzig: Gaertuer
Muijres FT, Johansson LC, Barfield R, Wolf M, Spedding GR, Hedenstrom A (2008) Leading-edge vortex improves lift in slow-flying bats. Science 319:1250–1253
Neuweiler G (2000) The biology of bats. Oxford University Press, Oxford
Nowak RN (1994) Walker’s bats of the world. Johns Hopkins University Press, Baltimore
Pennycuick CJ (1968) Power requirements for horizontal flight in the pigeon Columba Livia. J Exp Biol 49:527–555
Rayner JMV (1979) A vortex theory of animal flight. Part 2: the forward flight of birds. J Fluid Mech 91:731–763
Riskin DK, Willis DJ, Iriarte-Díaz J, Hedrick TL, Kostandov M, Chen J, Laidlaw DH, Breuer KS, Swartz SM (2008) Quantifying the complexity of bat wing kinematics. J Theor Biol 254:604–615
Sane SP (2003) The aerodynamics of insect flight. J Exp Biol 206:4191–4208. doi:10.1242/jeb.00663
Spedding GR (1986) The wake of a jackdaw (Corvus Monedula) in slow flight. J Exp Biol 125:287–307
Spedding GR (1987) The wake of a kestrel (Falco Tinnunculus) in flapping flight. J Exp Biol 127:59–78
Spedding GR, Rayner JMV, Pennycuick CJ (1984) Momentum and energy in the wake of a pigeon (Columba Livia) in slow flight. J Exp Biol 111:81–102
Spedding GR, Rosen M, Hedenström A (2003) 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. J Exp Biol 206:2313–2344. doi:10.1242/jeb.00423
Swartz SM, Groves MS, Kim HD, Walsh WR (1996) Mechanical properties of bat wing membrane skin. J Zool 239:357–378
Swartz SM, Bishop KL, Ismael-Aguirre M-F (2006) Dynamic complexity of wing form in bats: implications for flight performance. In: Akbar Z, McCracken G, Kunz T (eds) Functional and evolutionary ecology of bats. Oxford University Press, Oxford
Tian X, Iriarte-Diaz J, Middleton K, Galvao R, Israeli E, Roemer A, Sullivan A, Song A, Swartz S, Breuer K (2006) Direct measurements of the kinematics and dynamics of bat flight. Bioinspir Biomim 1:10–18
Tobalske BW, Hedrick TL, Dial KP, Biewener AA (2003a) Comparative power curves in bird flight. Nature 421:363–366
Tobalske BW, Hedrick TL, Biewener AA (2003b) Wing kinematics of avian flight across speeds. J Avian Biol 34:177–184
Willis DJ, Israeli ER, Persson P-O, Drela M, Peraire J, Swartz SM, Breuer KS (2007) A computational framework for fluid structure interaction in biologically inspired flapping flight. In: AIAA applied aerodynamics meeting, vol 1, pp 38–59, American Institute of Aeronautics and Astronautics Inc, Miami, United States, Reston, VA 20191–4344, United States
Acknowledgments
We thank A. Song, R. Waldman and D. Riskin for helpful discussions, and A. Sullivan, L. Macayeal and A. Robb for handling and training of animals and their help with data collection. We are very thankful for the support provided by D. Riskin regarding kinematic analysis and data flow issues. We also thank R. Waldman for the construction of the safety light barrier. We thank the Lubee Bat Conservancy, especially A. Walsh, for the long term access to the bats. This work was supported by the Air Force Office of Scientific Research, monitored by Drs. Rhett Jeffries, John Schmisser and Willard Larkin, and the National Science Foundation. All experiments were conducted with the authorization of the Institutional Animal Care and Use Committees of Brown University, the Lubee Bat Conservancy and the Division of Biomedical Research and Regulatory Compliance of the Office of the Surgeon General of the United States Air Force.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Hubel, T.Y., Hristov, N.I., Swartz, S.M. et al. Time-resolved wake structure and kinematics of bat flight. Exp Fluids 46, 933–943 (2009). https://doi.org/10.1007/s00348-009-0624-7
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00348-009-0624-7