Future aerodynamic machines can draw inspiration from a very unlikely source in the ocean: sharks. Researchers said in a new study that they had used shark skin to develop a structure that could improve aerodynamic performance of planes, wind turbines, drones and cars.
Sharks and airplanes, however, are not entirely different as their body shapes help them efficiently move through fluid (water and air) by generating lift and decreasing drag. The only notable distinction is the fact that sharks have about a 400-million-year advantage on the design process.
The study, published in the Journal of the Royal Society Interface, was conducted by evolutionary biologists and engineers at Harvard University, in collaboration with colleagues from the University of South Carolina.
"The skin of sharks is covered by thousands and thousands of small scales, or denticles, which vary in shape and size around the body," George Lauder, a professor at Harvard University and a co-author of the study, said in a statement. "We know a lot about the structure of these denticles — which are very similar to human teeth — but the function has been debated."
Unlike previous researches that focused on the drag-reducing properties of denticles, the latest study attempted to find if there was more to the story. The researchers wanted to know if the denticles were better suited for increasing lift.
As part of the study, they turned to the shortfin mako -- the fastest shark in the world -- which has three raised ridges, like a trident. The researchers used micro-CT scanning to create models of denticles in three dimensions. After that, they 3-D printed the shapes on the surface of a wing with a curved aerodynamic cross-section called an airfoil.
"We wanted to test these structures on airfoils as a way of measuring their effect on lift and drag for applications in the design of various aerial devices such as drones, airplanes, and wind turbines," August Domel, a Ph.D. student at Harvard, said.
The researchers tested 20 different configurations of denticle sizes, rows, and row positions on airfoils inside a water flow tank, and found that the denticle-shaped structures significantly increased lift acting as vortex generators.
"These shark-inspired vortex generators achieve lift-to-drag ratio improvements of up to 323 percent compared to an airfoil without vortex generators," Domel said. "With these proof-of-concept designs, we've demonstrated that these bioinspired vortex generators have the potential to outperform traditional designs."