Secrets of long-haul insect flight revealed
17 September 2009
Scientists studying the flexible wings of insects have discovered what makes them so efficient compared to the rigid wings of manmade aircraft.
Researchers at Oxford University and the University of New South Wales first used high-speed video cameras to capture how locust wings change shape in flight, then computer modelling to reconstruct these shape changes in 3D, and finally ran simulations to discover how they deliver the sort of efficient flight that enables tiny locusts to make inter-continental flights.
A report of their research is published in this week’s Science.
‘Until very recently it wasn’t possible to accurately model the wings of insects in flight – partly because they flap so fast and partly because their shape is very complicated,’ said Dr Graham Taylor of Oxford University’s Department of Zoology, an author of the paper. ‘But with faster cameras and our advanced 3D simulation technology we can now see that the reason locust wings are so efficient is that the wing’s complex, changing shape ensures that the air always flows smoothly over its surface, never becoming detached as it would with a flat wing. We showed that by channelling the airflow in this way insect wings produce about 50 per cent more lift than similar rigid wings.’
‘We always thought that insects, with their complicated wing structures full of twists, curves and ridges, must know something about aerodynamics that engineers don’t, now we know what that is,’ said Professor Adrian Thomas of Oxford University’s Department of Zoology, senior author of the paper. ‘It really is throwing down the gauntlet to engineers looking to build micro air-vehicles – telling them that if they want these tiny flapping aircraft to be efficient as well as powerful flyers then they will need to have wings that change shape just like an insect’s.’
In their study the researchers used images from multiple high-speed digital video cameras to reconstruct how the 3D shape of a locust's wing [the Desert locust: Schistocerca gregaria] changes in flight. They then used their 3D models in a computer simulation to predict the aerodynamic flow generated by the flapping wings, and when the flow predicted by the model was compared with experimental measurements from real insects it was an excellent match.
The team then re-ran their simulation with two simplified wing designs: In the first design they removed the wrinkles and curves but left the twist, while in the second design they replaced the wings with rigid flat plates.
The results were clear: the simplified models produced plenty of lift, but were much less efficient, requiring much more power for flight. The reason was that the complex deforming shape of the real wings allowed the air to flow smoothly over their surface, even as the wing was being flapped about. When the details of the real wings were lost, the flow separated away from the surface, resulting in high but costly lift. The consequences were dramatic: the fully deforming wings generated one and a half times the lift of the flat plate wings for the same amount of power.
Professor Adrian Thomas said: ‘The so-called `bumblebee paradox' - claiming that insects defy the laws of aerodynamics - is dead. Modern aerodynamics really can accurately model insect flight.’
For more information contact Professor Adrian Thomas on +44 (0)1865 271208 or email adrian.thomas@zoo.ox.ac.uk
Images and video of the locust flight modelling are available at: http://www.ox.ac.uk/media/news_releases_for_journalists/090915.html
Alternatively, contact the University of Oxford Press Office on +44 (0)1865 283877 or email press.office@admin.ox.ac.uk