By James Dacey
Fans of Radiohead may think this is straight out of the band’s video to their beautifully haunting single, Street Spirit (Fade Out), released back in 1996.
It is actually a demonstration of how the swallowtail butterfly manages to overcome the odds and fly in a straight line despite its unfavourable body shape. (Very Radiohead!)
Hiroto Tanaka at Harvard University and Isao Shimoyama at the University of Tokyo have built a model to mimic the wing motion and wing shape of the swallowtail, which even includes the thin membranes and veins that cover its wings.
Found on all continents except Antarctica, swallowtails are unique among butterflies because their wing area is very large relative to their body mass. This, combined with their overlapping fore wings, means that their flapping frequency is comparatively low and their general wing motion severely restricted.
As a result, swallowtails’ ability to actively control the aerodynamic force of their wings is limited. Their body motion is a passive reaction to the simple flapping motion, and not – as is common in other types of butterfly – an active reaction to aerodynamics.
Using motion analysis software, the researchers were able to monitor the ornithopter’s aerodynamic performance, showing that flight can be realized with simple flapping motions without feedback control, a model that can be applied to future aerodynamic systems.
This research was published yesterday in the journal Bioinspiration & Biomimetics.