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Spanwise flow and the attachment of the leading-edge vortex on insect wings


The flow structure that is largely responsible for the good performance of insect wings has recently been identified as a leading-edge vortex1,2. But because such vortices become detached from a wing in two-dimensional flow1, an unknown mechanism must keep them attached to (three-dimensional) flapping wings. The current explanation, analogous to a mechanism operating on delta-wing aircraft, is that spanwise flow through a spiral vortex drains energy from the vortex core3. We have tested this hypothesis by systematically mapping the flow generated by a dynamically scaled model insect while simultaneously measuring the resulting aerodynamic forces. Here we report that, at the Reynolds numbers matching the flows relevant for most insects, flapping wings do not generate a spiral vortex akin to that produced by delta-wing aircraft. We also find that limiting spanwise flow with fences and edge baffles does not cause detachment of the leading-edge vortex. The data support an alternative hypothesis—that downward flow induced by tip vortices limits the growth of the leading-edge vortex.

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Figure 1: Maximum axial flow occurs behind the leading-edge vortex.
Figure 2: The leading edge vortex (LEV) remains attached despite experimental manipulation.
Figure 3: Induced downwash lowers both the aerodynamic angle of attack and the lift generated by the LEV.


  1. Dickinson, M. H. & Götz, K. G. Unsteady aerodynamic performance on model wings at low Reynolds numbers. J. Exp. Biol. 174, 45–64 (1993).

    Google Scholar 

  2. Ellington, C. P. The aerodynamics of hovering insect flight. IV. Aerodynamic mechanisms. Phil. Trans. R. Soc. Lond. B 305, 79–113 (1984).

    Article  Google Scholar 

  3. Ellington, C. P., Van den Berg, C., Willmott, A. P. & Thomas, A. L. R. Leading-edge vortices in insect flight. Nature 384, 626–630 (1996).

    Article  CAS  Google Scholar 

  4. Van den Berg, C. & Ellington, C. P. The three-dimensional leading-edge vortex of a ‘hovering’ model hawkmoth. Phil. Trans. R. Soc. Lond. B 352, 329–340 (1997).

    Article  Google Scholar 

  5. Sunada, S., Sakaguchi, A. & Kawachi, K. Airfoil section characteristics at low Reynolds number. J. Fluids Eng. 119, 129–135 (1997).

    Article  CAS  Google Scholar 

  6. Kyia, M. & Arie, M. A contribution to an inviscid vortex-shedding model for an inclined flat plate in uniform flow. J. Fluid Mech. 82, 223–240 (1977).

    Article  Google Scholar 

  7. Sarpkaya, T. An inviscid model of two-dimensional vortex shedding for transient and asymptotically steady separated flow over an inclined plane. J. Fluid Mech. 68, 109–128 (1975).

    Article  Google Scholar 

  8. Dickinson, M. H., Lehmann, F. O. & Sane, S. P. Wing rotation and the aerodynamic basis of insect flight. Science 284, 1954–1960 (1999).

    Article  CAS  Google Scholar 

  9. Willmott, A. P., Ellington, C. P. & Thomas, A. L. R. Flow visualization and unsteady aerodynamics in the flight of the hawkmoth Manduca sexta. Phil. Trans. R. Soc. Lond. B 352, 303–316 (1997).

    Article  Google Scholar 

  10. Kücheman, D. The Aerodynamic Design of Aircraft (Pergamon, Oxford, 1978).

    Google Scholar 

  11. Maxworthy, T. Experiments on the Weis-Fogh mechanism of lift generation by insects in hovering flight Part 1. Dynamics of the ‘fling’. J. Fluid Mech. 93, 47–63 (1979).

    Article  Google Scholar 

  12. Liu, H., Ellington, C. P., Kawachi, K., Van den Berg, C. & Willmott, A. A computational fluid dynamic study of hawkmoth hovering. J. Exp. Biol. 201, 461–477 (1998).

    PubMed  Google Scholar 

  13. Dickinson, M. H. The effects of wing rotation on unsteady aerodynamic performance at low Reynolds numbers. J. Exp. Biol. 192, 179–206 (1994).

    CAS  PubMed  Google Scholar 

  14. Wang, J. Two dimensional mechanism for insect hovering. Phys. Rev. Lett. 85, 2216–2219 (2000).

    Article  Google Scholar 

  15. Milne-Thomson, L. M. Theoretical Aerodynamics (Macmillan, New York, 1966).

    MATH  Google Scholar 

  16. May, R. M. in Diversity of Insect Faunas (eds Mound, L. A. & Waloff, N.) 188–204 (Blackwell Scientific, London, 1978).

    Google Scholar 

  17. Dudley, R. The Biomechanics of Insect Flight. Form, Function, Evolution (Princeton Univ. Press, Princeton, 2000).

    Google Scholar 

  18. Willmott, A. P. & Ellington, C. P. The mechanics of flight in the hawkmoth Manduca sexta. II. Aerodynamic consequences of kinematic and morphological variation. J. Exp. Biol. 200, 2723–2745 (1997).

    CAS  PubMed  Google Scholar 

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We thank C. Ellington, M. Gahrib, G. Lauder, S. Sane and J. Wang for comments and suggestions on this manuscript. This work was supported by the National Science Foundation, Office of Naval Research, and DARPA.

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Correspondence to Michael H. Dickinson.

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Birch, J., Dickinson, M. Spanwise flow and the attachment of the leading-edge vortex on insect wings. Nature 412, 729–733 (2001).

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