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Celebrating America's Competitive Edge
A swimsuit like shark skin? Not so fast
For swimmers looking to gain an edge on their competition, the notion that simply donning a high-tech swimsuit — the surface of which was inspired by shark skin — could lead to a first-place finish is powerful.
It’s also one that’s almost completely misplaced, said George Lauder, the Henry Bryant Bigelow Professor of Ichthyology.
Experiments conducted in Lauder’s lab and described in the Feb. 9 issue of the Journal of Experimental Biology reveal that, while sharks’ sandpaperlike skin does allow the animals to swim faster and more efficiently, the surface of swimsuits such as the Speedo Fastskin II has no effect when it comes to reducing drag as swimmers move through the water.
“In fact, it’s nothing like shark skin at all,” Lauder said of such swimsuit material. “What we have shown conclusively is that the surface properties themselves, which the manufacturer has in the past claimed to be biomimetic, don’t do anything for propulsion.”
That’s not to say that the suits as a whole do nothing to improve performance.
“There are all sorts of effects at work that aren’t due to the surface,” Lauder said. “Swimmers who wear these suits are squeezed into them extremely tightly, so they are very streamlined. They’re so tight they could actually change your circulation and increase the venous return to the body, and they are tailored to make it easier to maintain proper posture even when tired. I’m convinced they work, but it’s not because of the surface.”
By comparison, Lauder said, the research showed that the millions of denticles — tiny, toothlike structures — that make up shark skin have a dramatic effect on how the animals swim by both reducing drag and increasing thrust.
“What we found is that as the shark skin membrane moves, there is a separation of flow. The denticles create a low-pressure zone, called a leading-edge vortex, as the water moves over the skin,” he said. “You can imagine this low-pressure area as sucking you forward. The denticles enhance this leading-edge vortex. So my hypothesis is that these structures that make up shark skin reduce drag, but I also believe them to be thrust-enhancing.”
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