Fastest Swimming Insect Could Inspire Uncrewed Boat Designs
taylorvich writes:
https://phys.org/news/2024-01-fastest-insect-uncrewed-boat.html
Whirligig beetles, the world's fastest-swimming insect, achieve surprising speeds by employing a strategy shared by speedy marine mammals and waterfowl, according to a new Cornell University study that rewrites previous explanations of the physics involved.
The centimeter-long beetles can reach a peak acceleration of 100 meters per second and a top velocity of 100 body lengths per second (or one meter per second).
Not only do the results explain the whirligig's Olympian speeds, but they also offer valuable insights for bio-inspired designers of near-surface water robots and uncrewed boats.
Until now, researchers have believed that whirligigs attain their impressive speeds using a propulsion system called drag-based thrust. This type of thrust requires the insect's legs to move faster than the swimming speed, in order for the legs to generate any thrust. For the whirligig beetle to achieve such fast swimming speeds, its legs would need to push against the water at unrealistic speeds.
"It could have well been questioned," said Chris Roh, assistant biological and environmental engineering professor. "The fastest swimmer and drag-based thrust don't usually go together in the same sentence."
In fact, fast-swimming marine mammals and waterfowls tend to forgo drag-based thrust in favor of lift-based thrust, another propulsion system. The finding was described in a study published Jan. 8 in the journal Current Biology.
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Using two high-speed cameras synchronized at different angles, the researchers could film a whirligig and observe a lift-based thrust mechanism at play. Lift-based thrust works like a propeller, where the thrusting motion is perpendicular to the water surface, eliminating drag and allowing for more efficient momentum capable of greater speed.
More information: Yukun Sun et al, Whirligig beetle uses lift-based thrust for fastest insect swimming, Current Biology (2024). DOI: 10.1016/j.cub.2023.11.008
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