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The secret right under our (bottle)noses: What dolphins can teach us about hydrodynamics

The flippers that some marine mammals use to glide underwater have a lot in common with the wings of passenger jets and fighter planes.

An interdisciplinary team of scientists from Duke University, West Chester University and the United States Naval Academy recently found out just how similar the manmade wings and marine mammal flippers are by testing scale models in a water tunnel.

“Ultimately, the goal is to have a better understanding of how an animal moves and maneuvers,” says Laurens Howle, a professor of mechanical engineering and materials science at Duke, and co-author of the study in The Journal of Experimental Biology. “This [research] is one small step along that road.”

He and his colleagues wanted to know how much energy some dolphins, whales and porpoises use to replace the water in their path—a question that straddles biology and engineering. “A biologist looks inside-out; an engineer looks outside-in,” Howle told ScientificAmerican.com.

All seven species studied have relatively immobile flippers that remain outstretched like an airplane’s wings. Two general shapes were identified, differing in their capacity to generate lift and overcome drag. The bottlenose dolphin’s almost triangular flippers are the most efficient hydrodynamically. The shape means the dolphin “produces the greatest amount of lift for paying the least amount of drag cost,” says Howle. The harbor porpoise paddles along at the other end of the spectrum with flippers about two and a half times less efficient than those of the bottlenose.

A Boeing 737’s triangular wings were designed with efficiency in mind, but “modern fighter jets are more delta-shaped,” says Howle. “They have plenty of power, so they don’t need to be concerned about efficiency.” He adds that this shape, shared with the harbor porpoise, is necessary for reaching supersonic speeds. “Not that that’s anything an animal will ever be concerned about.”

The U.S. Navy is funding further research into how to apply nature’s handiwork to its own technology. Howle doesn’t expect the findings to influence the design of the next fighter jet, but a little biomimicry may improve future submarines.

Picture of bottlenose dolphin by FourOaks vis iStockPhoto.

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