A team of evolutionary biologists and engineers have published in the Journal of the Royal Society Interface a research wich have demonstrated a new structure inspired by shark skin that could improve the aerodynamic performance of planes, wind turbines, drones, and cars.
Sharks and airplanes aren’t actually all that different. Both are designed to efficiently move through fluid (water and air), using the shape of their bodies to generate lift and decrease drag. The difference is, sharks have about a 400 million-year head start on the design process.
The skin of sharks is covered by thousands and thousands of small scales, or denticles, which vary in shape and size around the body. These denticles are very similar to human teeth, but their function has been debated.
Most research has focused on the drag reducing properties of denticles but the researcher team wondered if there was more to the story.
What if instead of mainly reducing drag, these particular shapes were actually better suited for increasing lift?
To help test that hypothesis, the researchers collaborated with a team of engineers and, for inspiration, they turned to the shortfin mako, the fastest shark in the world. The mako’s denticles have three raised ridges, like a trident. Using micro-CT scanning, the team imaged and modeled the denticles in three dimensions. Next, they 3-D printed the shapes on the surface of a wing with a curved aerodynamic cross-section, known as an airfoil.
“Airfoils are a primary component of all aerial devices,” said August Domel, a Ph.D. student at Harvard and co-first author of the paper. “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.
fThe researchers found that in addition to reducing drag, the denticle-shaped structures significantly increased lift, acting as high-powered, low-profile vortex generators.
Cars and planes are equipped with these small, passive devices designed to alter the air flow over the surface of a moving object to make it more aerodynamic. Most vortex generators in the field today have a simple, blade-like design.
“These shark-inspired vortex generators achieve lift-to-drag ratio improvements of up to 323 percent compared to an airfoil without vortex generators,” said Domel. “With these proof of concept designs, we’ve demonstrated that these bioinspired vortex generators have the potential to outperform traditional designs.”
“You can imagine these vortex generators being used on wind turbines or drones to increase the efficiency of the blades,” said Katia Bertoldi, William and Ami Kuan Danoff Professor of Applied Mechanics at SEAS and co-author of the study. “The results open new avenues for improved, bioinspired aerodynamic designs.”