Soon, maple seeds inspired ‘micro helicopters’ to soar the skies

June 12th, 2009 - 12:39 pm ICT by ANI  

Washington, June 12 (ANI): In a new research, scientists have described the aerodynamic secret of twirling seeds of maple trees, which might have implications for the design of swirling parachutes and micro-helicopters.

The research was done by scientists from Wageningen University in the Netherlands and the California Institute of Technology (Caltech), US.

The research, led by David Lentink, an assistant professor at Wageningen, and Michael H. Dickinson, the Zarem Professor of Bioengineering at Caltech, revealed that, by swirling, maple seeds generate a tornado-like vortex that sits atop the front leading edge of the seed as they spin slowly to the ground.

This leading-edge vortex lowers the air pressure over the upper surface of the maple seed, effectively sucking the wing upward to oppose gravity, giving it a boost.

The vortex doubles the lift generated by the seeds compared to nonswirling seeds.

This use of a leading-edge vortex to increase lift is remarkably similar to the trick employed by insects, bats, and hummingbirds when they sweep their wings back and forth to hover.

The finding means that plants and animals have converged evolutionarily on an identical aerodynamic solution for improving their flight performance.

To measure the flow of air created by swirling seeds, the scientists built plastic models of the seeds with radii of about five inches, or 5 to 10 times larger than a maple seed.

The seeds were spun through a large tank of mineral oil using a specially designed robot, modified from a device at Caltech called “Robofly.”

Next, the scientists used a powerful laser to create a sheet of light that illuminated tiny glass beads added to the oil. They then used a camera to capture images of the motion of the beads as the model seed spun through the tank.

The images revealed the presence of a tornado-like vortex lying near the front leading edge of the spinning seed.

Force measurements attached to the model showed that the swirling vortex created extra lift that would act to slow the descent of a seed as it spun to the ground.

The research might have implications for the design of swirling parachutes-which have been designed by space agencies to slow the descent of future planetary probes exploring the atmospheres of planets such as Mars-and of micro-helicopters.

“Maple seeds could represent the most basic and simple design for a miniature helicopter, if the swirling wing could be powered by a micromotor,” said Lentink.

“This is still an open challenge for future aerospace engineers, and our aerodynamic study of maple seeds could help design the first successful powered ‘maple’ helicopters,” he added. (ANI)

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