Last updated April 18, 2018 at 9:33 am
The way sharks move through water may help us design better planes, drones and wind turbines.
The shorten mako is the fastest shark in the ocean and can grow to 4.45 metres. Credit: Corey Ford/iStock
A shark’s body allows it to move efficiently and almost effortlessly through water.
That’s not great news if you’re in the water nearby at the time, but it has provided inspiration for a group of researchers interested in making things move more efficiently in the air.
The key lies is the thousands and thousands of small scales called denticles that cover a shark’s skin and vary in size and shape depending on where they are on the body.
Until now, the greatest interest has been in the drag reducing properties of these denticles, but a team of evolutionary biologists and engineers at Harvard University and the University of South Carolina, started to suspect that they also increase lift.
To help test that hypothesis, they turned to no less that the fastest shark in the world, the shortfin mako, which has three raised ridges of denticles, like a trident.
Environmental scanning electron microscope image of denticles from the shortfin mako shark (a) and (its corresponding parametric 3D model (b). These denticles were arranged in a wide range of different configurations on an aerofoil, two examples of which are shown here (c,d ). (Image courtesy of Harvard University)
Using micro-CT scanning, they imaged and modelled the denticles then 3D-printed the shapes onto the surface of a wing with a curved aerodynamic cross-section, known as an aerofoil or airfoil.
“Airfoils are a primary component of all aerial devices,” said co-first author August Domel, a Harvard PhD student.
“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.”
The researchers tested 20 different configurations of denticle sizes, rows and row positions on aerofoils inside a water flow tank and found that they significantly increased lift, acting as high-powered, low-profile vortex generator.
Vortex generators are fitted to cars and planes to alter the air flow over their surface and make them more aerodynamic. Most 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’ve demonstrated that these bioinspired vortex generators have the potential to outperform traditional designs.”
The paper was published in the Journal of the Royal Society Interface.
