Friday 24 October, 2014

Dragonfly’s stability in flight inspires micro wind turbine design

Published On: Thu, Feb 3rd, 2011 | Science | By BioNews

Micro wind turbines that can withstand gale-force winds are being developed with the technology that allows a dragonfly to remain stable while in flight.

Micro wind turbines work very well in light winds, but when there is a storm they tend to spin faster, and that can put a lot of pressure on their generators.

The technology used, to solve this problem, is very expensive and it is not covered by the amount of electricity the wind turbines produce, so a study on the technique a dragonfly uses to remain in flight was conducted.

It was seen that when air passes by a dragonfly’s thin wings, tiny peaks on their surface create a series of swirling vortices.

Aerospace engineer Akira Obata of Nippon Bunri University in Oita, Japan, decided to study how these vortices affect the dragonfly’s aerodynamics.

Obata filmed a model dragonfly wing as it moved through a large tank of water laced with aluminium powder, and noticed that the water flowed smoothly around the vortices, with little drag at low speeds.

The flow of water around the dragonfly wing stayed the same even at varying low current speeds, but its aerodynamic performance fell drastically as either water speed or the wing’s size increased.

Using what they have discovered, Obata and his colleagues developed a low-cost model of a micro wind turbine whose 25-centimetre-long paper blades incorporated bumps like a dragonfly”s wing.

During trials, the wind speed over the blades rose from 24 to 145 kilometres per hour, but the flexible blades bent into a cone instead of spinning faster.

The researchers said the prototype generates less than 10 watts of electricity, which would be enough to recharge cellphones or light LEDs.

“It’s a clever leap,” said David Alexander, a biomechanics specialist at the University of Kansas.

“In some ways it’s more appropriate than using an animal wing model for an airplane. A wind turbine blade is just a wing, only it’s designed to go in tight circles,” he stated.

But Wei Shyy of the Hong Kong University of Science and Technology believes that while the dragonfly-inspired design may be more stable, it will also experience more energy loss in terms of drag. (ANI)

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