Carried by the wind, dandelion seeds can travel enormous distances of more than a kilometer (0.6 miles). Now, researchers at The University of Edinburgh have discovered that this is thanks to a remarkable form of flight never before seen in nature.
The distances are achieved because of what the researchers call "the separated vortex ring" which sees the seed bristles, collectively called the pappus, create ring-shaped air bubbles. These form vertically above the pappus, increasing air-resistance and slowing descent much like a parachute.
Remarkably, the air bubble is actually made more stable as air flows through it. And that flow is regulated by the particular spacing of the seed's bristles. Perhaps counter-intuitively it's the relatively high porosity of the pappus that helps keep its flight stable.
Above: The separated vortex ring can be seen in the right-hand image
To analyze the seeds, the team built a vertical wind tunnel honed such that the seed would hover at a sustained height. The researchers used a mixture of long-exposure photography and high-speed imaging to analyze the flow of air through and around the pappus. They also used X-ray imaging and microscopes to examine the morphology of the dandelions themselves.
According to the researchers the dandelion's seeded form is four times more efficient in maintaining altitude than a human-made parachute.
Though dandelion seeds can travel more thank 1 km, they typically land within 2 meters (6.6 feet) of the flower. However, the seeds of other flowers in the Asteraceae, which also includes daisies and sunflowers, can disperse more than 150 km (93 miles).
The researchers speculate that this form of travel could inform the design of tiny airborne drones which require no power supply and that could, say, monitor air pollution.
The team's research, A separated vortex ring underlies the flight of the dandelion, was published in the journal Nature.
Source: The University of Edinburgh
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