Biophysics

Flying in Two Dimensions

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Science  22 Sep 2000:
Vol. 289, Issue 5487, pp. 2005
DOI: 10.1126/science.289.5487.2005d

Although airplanes and animals fly in three dimensions, the basic way in which a moving fixed wing produces lift can be modeled as a two-dimensional flow (the familiar contours showing faster flow above the wing and slower flow beneath). The much greater difficulties in modeling the non-fixed wings characteristic of insect flight have suggested that the basic process may be truly three-dimensional and may depend on eddy-like currents moving up or down the wing surfaces. Wang now shows that two-dimensional flows are sufficient to produce lift for the case of the “figure-eight” wing motion seen for most flying insects, such as dragonflies and fruit flies. She solves the appropriate Navier-Stokes equation numerically to the fourth order and finds that this motion not only can create lift-producing vortices but also will shed them to avoid interference with those created in the next cycle of wing strokes. — PDS

Phys. Rev. Lett.85, 2216 (2000).

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