January 21, 2021 | David F. Coppedge

Delicate Acrobats: Butterflies and Jellyfish Use Physics to Perfection

Two animals probably not envisioned as champion movers can teach human designers a thing or two.

Butterflies

They certainly look dainty on the wing with their rich colors and flapping works of art, but scientists did not think butterflies were among the best flyers in the insect world, with those large, clumsy-looking wings that look inefficient for flight. Matt McGrath sets the record straight in his article and video for the BBC News, “Natural wonder: Wing ‘clap’ solves mystery of butterfly flight.”

Researchers have struggled to understand how these delicate creatures can fly with their large but inefficient wings.

Now, a new study shows that butterflies evolved an effective way of cupping and clapping their wings to generate thrust.

Illustra Media: MetamorphosisThe large wings, it turns out, generate a quick clap against a pocket of air that gives them more thrust than smaller wings could.

The team found that the flexible wings dramatically increased the force created by the clap.

It also improved the efficiency by 28%, which the authors describe as a huge amount for a flying animal.

The researchers take a quick detour into the Darwine bar:

This leads them to conclude that the large wings and cupped, clapping action were an evolutionary advantage for butterflies when faced with predators.

No! It is not an “evolutionary” advantage. It’s just an advantage. That’s like saying that a spoiler on a sports car is an evolutionary advantage, because it “emerged” from a mistake on the bumper.

If you haven’t watched Illustra’s documentary Metamorphosis yet, take an hour to be mesmerized by these tiny champions whose wonders go far beyond just flight finesse.

Jellyfish

Did you know that jellyfish are considered some of the most efficient swimmers in the ocean? That may seem surprising, watching the repetitive pulses of the bell and the small distance covered. But even though jellyfish are far removed from butterflies on “Darwin’s tree,” they use a similar physical mechanism to increase thrust. Phys.org reports from the work of University of South Florida that these animals, considered simple or primitive to evolutionary biologists, create a ‘virtual wall’ to enhance performance.

Moon jellies in an aquarium (DFC).

New research led by the University of South Florida has uncovered one of the reasons jellyfish have come to be known as the “world’s most efficient swimmer.” Brad Gemmell, associate professor of integrative biology, found jellyfish produce two vortex rings, which are donut-shaped bodies of fluid underneath their translucent bodies, that spin in opposite directions. They appear as jellyfish squeeze and reopen throughout each swim cycle, providing a ‘ground effect’ force as if they were to be pushing off the seafloor.

Never before has it been seen that an animal can produce this effect. It works amazingly well, producing extra thrust without the harm of cavitation bubbles.

Gemmell captured the motion by recording the movements of eight jellyfish swimming in a glass filming vessel using a high-speed digital camera at 1,000 frames per second. He and his colleagues witnessed jellyfish that were in motion had a 41% increase in maximum swimming speed and a 61% increase in cumulative distance traveled per swimming cycle compared to those starting from rest.

Olympic swimmers gain an advantage from pushing off the wall at the end of each lap. Jellyfish have a way to get this effect out in the open water. You can watch a bit of the high-speed footage in the article.

 

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