Sharks have been around since before dinosaurs roamed the earth, which has given them plenty of time to perfect the art of aerodynamics. It's no surprise then that sharks, like whales, can teach us a thing or two about more efficiently moving through both water and air. A team of biologists and engineers from Harvard University and the University of South Carolina have taken a fresh look shark scales in the hope of making drones, planes and wind turbines more efficient.
Shark skin is covered in denticles, thousands of small scales, varying in shape and size for different parts of its body. Sharks use the shape of their bodies to increase lift and decrease drag as they move through water, and airplanes do the same thing to move through the air, making the fish ideal for research into airfoils – the aerodynamic cross-section of a plane wing.
"We know a lot about the structure of these denticles – which are very similar to human teeth – but the function has been debated," says George Lauder, co-author of the research.
Most research on shark scales has looked at how they affect drag, but Launder and his team instead concentrated on lift.
Specifically, the researchers looked at the shortfin mako, the fastest shark in the ocean, using micro CT scanning on the shapes of its denticles, which have three raised ridges, to model and print them in 3-D. They printed the shapes onto an airfoil, testing it from inside a water flow tank using 20 different arrangements of denticle sizes, rows and row positions. They found that by acting as high-powered, low-profile vortex generators, the denticles on the airfoil significantly increased lift.
"These shark-inspired vortex generators achieve lift-to-drag ratio improvements of up to 323 percent compared to an airfoil without vortex generators," says August Domel, co-first author of the paper. "With these proof of concept designs, we've demonstrated that these bioinspired vortex generators have the potential to outperform traditional designs."
"The results open new avenues for improved, bioinspired aerodynamic designs," says Katia Bertoldi, William and Ami Kuan Danoff, who each co-authored the study.
The team's research was published in the Journal of the Royal Society Interface.
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