Have you ever thought that the butterfly, with its jerky fluttering flight, is a ‘primitive’ and inefficient flyer? After all, its wings don’t look even remotely aerodynamic, compared to the beautifully streamlined ‘aerofoil’ wings of birds and airplanes.
Indeed, just 10 years ago, conventional laws of aerodynamics could not explain how any of the insects could fly at all,1 let alone manoeuvre so masterfully at low speeds—hovering and flying backwards and sideways, in complete control.
In the last decade, however, researchers have uncovered a variety of ‘unconventional’ ways that these gossamer aeronauts use their wings to stay aloft.2 For example, one particular flapping movement creates a spiralling airflow (vortex) along the edges of the wings, generating some of the lift which ‘conventional steady-state aerodynamics’ could not account for.3
Now, after filming red admiral butterflies flying in a ‘wind tunnel’, researchers have been surprised by a whole range of complicated wing movements which generate more lift than simple flapping would do: ‘wake capture, two different types of leading-edge vortex, active and inactive upstrokes, in addition to the use of rotational mechanisms and the Weis-Fogh “clap-and-fling”? mechanism’.4 What is more, the red admirals often used completely different mechanisms on successive wing strokes!…
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