Jellyfish create a screen effect away from the surface to swim 41% faster

A new study from the University of South Florida reveals one of the reasons why jellyfish have become known as the world’s most efficient swimmers. They create a screen effect by floating in the water. It was first discovered that the ground effect was created away from a solid surface.

Brad Gemmell, associate professor in the Department of Integrative Biology, discovered that jellyfish produce two vortex rings, which are donut-shaped bodies of fluid that form under the jellyfish and spin in opposite directions. They appear as jellyfish collapsing and reopening during each swim cycle, creating a ground effect (ground or ground effect) as if they were pushing off the seabed.

The screen effect is best known on airport runways. During takeoff, the air is compressed between the aircraft and the ground, which creates pressure and force that enhances performance. Gemmell’s experiments showed that jellyfish can use their two vortex rings instead of earth. The vortex rings confront each other, effectively creating a wall that provides a similar performance gain compared to animals that swim at the bottom. Never before has it been proven that an animal can create this phenomenon far from a solid boundary.

“The fact that these simple animals have figured out how to achieve ground effect amplification in open water, away from any hard surfaces, has the potential to open up a number of new possibilities for engineering vehicles to take advantage of this phenomenon.”

Brad Gemmell, Associate Professor, Department of Integrative Biology

The scientist also captured the movement of eight jellyfish floating in a glass imaging vessel using a high-speed digital camera at 1000 frames per second. He and his colleagues saw jellyfish that were on the move had a 41% increase in maximum swimming speed and an increase in cumulative distance traveled per swim cycle compared to jellyfish that started swimming from rest.

Unlike propellers, jellyfish do not form cavitation bubbles (bubbles in an aqueous medium, followed by their collapse and the release of a large amount of energy, which is accompanied by noise and hydraulic shocks) and at the same time they are silent, which allows them to move calmly in water. Their high swimming efficiency also helps them store energy for growth and reproduction. Researchers are now using jellyfish as a model to develop underwater vehicles that can be equipped with sensors that continuously monitor the state of the ocean and seabed. These new discoveries can help advance these technologies and deepen our understanding of the ocean.

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