November 24, 2010

Wind Tunnel Test Reveals Secrets Of Pterosaur Flight

Pterodactyls would have been skilled fliers in gentle tropical breezes, but blustery conditions would likely have sent them careening out of control, a University of Bristol engineer/paleontologist claims in a new study.

Colin Palmer, an engineer with four decades of experience who is also currently a doctorate student in the university's School of Earth Sciences, created models of pterodactyl wings out of thin, curved sheets of a carbon fiber and epoxy resin composite.

The 62-year-old then tested the creation in a wind tunnel, and discovered that, contrary to what some scientists have suggested, pterosaurs were able to fly quite well under the right conditions. According to the University of Bristol, Palmer's experiment is believed to mark the first time anyone has successfully demonstrated the two-dimensional characteristics of pterosaur wings.

In his research, Palmer found that the dinosaurs were able to land gently--a good thing, considering they are believed to have had extremely thin bones which could have broken in a rougher landing. However, he also discovered that pterodactyls were too slow and flexible to take advantage of stronger winds and, according to a University of Bristol press release, "were significantly less aerodynamically efficient and were capable of flying at lower speeds than previously thought."

"Pterosaur wings were adapted to a low-speed flight regime that minimizes sink rate," Palmer said in a statement on Tuesday. "This regime is unsuited to marine style dynamic soaring adopted by many seabirds which requires high flight speed coupled with high aerodynamic efficiency, but is well suited to thermal/slope soaring. The low sink rate would have allowed pterosaurs to use the relatively weak thermal lift found over the sea."

"Since the bones of pterosaurs were thin-walled and thus highly susceptible to impact damage, the low-speed landing capability would have made an important contribution to avoiding injury and so helped to enable pterosaurs to attain much larger sizes than extant birds," he added. "The trade-off would have been an extreme vulnerability to strong winds and turbulence, both in flight and on the ground, like that experienced by modern-day paragliders."

Palmer's research appears in the current issue of the journal Proceedings of the Royal Society B. Among his findings, according to BBC News Science Correspondent Pallab Ghosh, is that the bony front edge of the pterosaur wing created drag, thus making it less aerodynamically efficient than the feathery wings of modern birds.

"I come at this as an engineer rather than a paleontologist," Palmer told Ghosh on Tuesday. "Palaeontologists have done amazing work in understanding the anatomy of these animals and that gave me a huge amount of data to build on. But as an engineer and experimentalist my first reaction was I want to do some (modeling) and find out what's going on."

"This is the first time this has been done," he added. "Previously data has been taken from the aerodynamic literature and adapted it as best they could to make predictions of pterosaur flight performance. Now for the first time we've got data from (models of pterosaur wings)"¦ It's just a different approach. And I think this cross-disciplinary work is very important because it brings in new insights based on new perspectives."


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