It is 4 a.m. The moon is visible from my bedroom window, a faint crescent hopscotching between clouds and trees. I tear myself out of bed and stagger to the kitchen.
Sharks and airplanes are not 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, researchers said.
“The skin of sharks is covered by thousands and thousands of small scales, or denticles, which vary in shape and size around the body,” said George Lauder, professor at Harvard University in the US.
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 modelled the denticles in three dimensions. Next, they 3D 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 PhD student at Harvard. “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.”
High power generators
The researchers tested 20 different configurations of denticle sizes, rows and row positions on airfoils inside a water flow tank. They 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 per cent compared to an airfoil without vortex generators,” said Domel. “With these proof of concept designs, we have demonstrated that these bioinspired vortex generators have the potential to outperform traditional designs.”