Aircraft

Secrets of fish scale drag offer clues for more aerodynamic aircraft

Secrets of fish scale drag off...
Scientists have discovered that the overlapping areas on the surface of fish scales leads to a zig-zagging motion of fluid as it flows over the top
Scientists have discovered that the overlapping areas on the surface of fish scales leads to a zig-zagging motion of fluid as it flows over the top
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Scientists have discovered that the overlapping areas on the surface of fish scales leads to a zig-zagging motion of fluid as it flows over the top
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Scientists have discovered that the overlapping areas on the surface of fish scales leads to a zig-zagging motion of fluid as it flows over the top
Scientists have gained a new understanding of fish scales by studying the common carp
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Scientists have gained a new understanding of fish scales by studying the common carp

Scientists in Europe researching aerodynamic forces have opened up some interesting new avenues of study inspired by fish scales. This new understanding of the flow patterns over the surface of the creature’s skin was used to create bio-inspired fish scale arrays for further investigation, which the team believes could lead to drag reductions in aerial vehicles of as much as 25 percent.

Scientists regularly turn to the animal kingdom in their efforts to improve the aerodynamic performance of aircraft. In the past, we’ve looked at how the complex movements of locust wings could inspire more efficient aerial vehicles, while a 2018 study investigating the scales of shark skin is another interesting example.

Similarly, the authors of the new study from the City, University of London and the University of Stuttgart found inspiration in the way scales help fish move smoothly through the water. Like sharks, these creatures rely on highly-evolved arrays of tiny scales to minimize drag as they swim, and by studying the surface topology of European sea bass and common carp, scientists have now uncovered some useful secrets.

Scientists have discovered that the overlapping areas on the surface of fish scales leads to a zig-zagging motion of fluid as it flows over the top
Scientists have discovered that the overlapping areas on the surface of fish scales leads to a zig-zagging motion of fluid as it flows over the top

The team’s investigations were carried out using digital microscopes and then computer modeling to geometrically reconstruct the intricate patterns. The scientists discovered that the overlapping areas on the surface of the fish leads to a zig-zagging motion of fluid as it flows over the top.

This in turn creates a “streaky flow” that neutralizes unstable oscillations which commonly lead to turbulence, called Tollmien–Schlichting waves. Ultimately, the scientists report that the zig-zag motion and streaky flow it produces reduces skin friction drag by more than 25 percent.

This effect was observed again in a bio-inspired fish scale array fixed to a plate, which was experimented with alongside a smooth plate inside a laminar water tunnel at the University of Stuttgart. If similar effects could be produced by applying these artificial fish scale arrays to aerodynamic surfaces, they could play an important role in the development of aerial vehicles that travel faster and use less fuel.

The team’s research was published in the journal Scientific Reports and in the Journal of Experimental Biology.

Source: City, University of London

5 comments
Nobody
From my old days of swimming with dolphins, I would think their skin would be a more efficient model of turbulence reduction. I was always amazed how an eight foot animal could zoom past me a couple feet away and I never felt the the water move. If I wasn't looking I wouldn't even know it was there.
PB
This isn't new ....... if you go back to the America's Cup after the Australians won with their keel design, the concept of fish scales and grooving, both to reduce drag, was discussed, and may have been implemented. It has also been discussed for aircraft, but while the fish scale option has been examined it also adds to icing accretion, and it collects dirt and has a negative affect.
Fish Scales is a great concept, and it works, but has issues and is not adaptable for as many uses as one might imagine.
drBill
I'd like to see the application of scales to ships, in the sea, where the advantage arose.
1stClassOPP
Methinks if you applied low air pressure, allowing air to escape between the scales (engine exhaust perhaps) you could greatly improve efficiency of water craft, but maybe air craft as well.
I learned from an old wooden boat builder as story about him building a sail boat for youth competition and him not having the time to properly sand the hull smooth. The result he said, was that he won the competition, crediting the “rough” finish of his hull, causing it to not “stick” to the water. I’ve never forgotten that principle bu never had an opportunity to verify his conclusion. I’d love to work with someone willing to try out the fish scale theory.
Dariusz Jan
The slippery slime that covers the fishes scales is the magic coating letting fish swim in water with very little resistance.
For flying in air with little resistance birds of the feathers should be of interest, or dimpled golf balls.