From Sea to Sky: the Aerodynamics of Sharkskin
You might think that you’d want the smoothest surface possible to reduce drag, but believe it or not that’s actually not the case!
This article popped up for me on LinkedIn a few weeks ago, and I absolutely love talking about biomimetics (the study of how nature’s systems can inspire solutions to human problems). So now you get to learn about this stuff!
Boom Supersonic is designing a new generation of supersonic passenger aircraft, and as part of that they are testing a new material made by a company called MicroTau. This material is covered in tiny surface imperfections called “riblets.” These riblets help reduce drag via similar physical principles as what make golf balls with dimples fly better.
Pretty much all fluids (air or liquid) flowing over an object will end up becoming turbulent very quickly: this means that instead of all the molecules traveling in nice parallel lines, they’ll start wobbling around and moving in circular patterns, called vortices.
On shark scales—which is where the inspiration for this new material came from—riblets help to reduce how much this turbulent flow moves side to side, and channel the flow in the primary direction of travel. They also help push some of these vortices up and away from the scales, which reduces how much friction the vortices cause because they’re making less contact with the surface of the scale. Less friction + less sideways motion = less drag!
I wanted to be a zookeeper growing up and still love animals, and both our modern species and those in the fossil record have SO many amazing adaptations we can learn from. It always makes me excited to see the ways biomimetics are being applied in my current field.
One last fun fact: on sharks these textured scales are called “denticles”, because they’re covered in dentin. Yes, that’s the same dentin as in your own teeth! These denticles also have a central pulp cavity.
Sharks are basically covered in teeth. You’re welcome.
Always cite your sources, folks—I referenced this paper for a nice explanation of how riblets actually work on sharks. It has a lot of interesting details about other adaptations too, especially in prehistoric fishes: Hydrodynamics of fossil fishes