dragonfly wings


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dragonfly wings (62K bytes)

Dragonfly wings - note the more reinforced structure in the leading third of each wing

Dragonflies are very manoeuvrable in flight. The flight muscles can adjust stroke-frequency, amplitude, phase between forewings and hindwings, and angle of attack independently for each of the four wings. For the purposes of description, four main flying modes are recognised:

  • counter-stroking, in which forewings and hindwings move up and down about 180 out of phase - this pattern is generally used in cruising flight

  • phased-stroking, where the hindwings cycle about 90 before the forewings - this provides more acceleration for manoeuvres

  • synchronised-stroking, where the forewings and hindwings move in unison

  • gliding, where the wings are held without beating for free gliding, gaining lift in updrafts, or during mating

Dragonflies use a variety of lift-inducing mechanisms, for example classical lift at low angles of attack, supercritical lift at high angles of attack close to the stall, vortex production, especially along the leading edge of the forewings, and vortex-shedding. The angle of attack is the most important variable controlling aerodynamic mechanisms (Thomas et al, 2004)

References

Rowe, R.J. http://tolweb.org/notes/?note_id=2471 (accessed 3/11/05).

Thomas, A.L.R., Taylor, G.K., Srygley, R.B., Nudds, R.L., and Bomphrey, R.J. (2004) Dragonfly flight: free-flight and tethered flow visualisations reveal a diverse array of unsteady lift-generating mechanisms, controlled primarily via angle of attack. Journal of Experimental Biology, 207, 4299-4323.


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