Researchers Publish Study on Jellyfish Energy Consumption That Will Improve Bio-Inspired Robotic Designs for Navy
This story is from the category Embodiment
Date posted: 22/10/2013
Virginia Tech College of Engineering researchers are part of a national study that has cracked how jellyfish move with the lowest cost of transport of any animal. The findings will be used as researchers continue to design bio-inspired jellyfish for the U.S. Navy.
Published in a recent issue of the Proceedings of National Academy of the Sciences (http://www.pnas.org) , the study highlights jellyfish as one of the most energetically efficient natural propulsors on the planet. Researchers found that rather than moving continuously through water while swimming, jellyfish use a critical pause between the contraction and expansion of their bell-shaped body to create a vortex that pushes them forward. In essence, the creature displaces the water behind them, creating a “hole” that when re-filled propels them forward.
This feat of motion allows the creature to travel 30 percent farther each stroke cycle, thereby reducing metabolic energy demand by swimming muscles, said Shashank Priya (https://www.me.vt.edu/_bios/_primary/priya_bio.html), professor of mechanical engineering (http://www.me.vt.edu) and Turner Fellow, who led Virginia Tech efforts on the project. “The fluid is helping the jellyfish to move and conserve the energy,” he said. “The fluid is actually pushing them, and when that energy dissipates, they contract again.”
Researchers also found that the jellyfish in the study displayed a lower cost of transport – the amount of food and oxygen taken in by the body, versus energy spent in movement– 48 percent lower than other animals in similar studies. This quick action with minimal spent also helps jellyfish in hunting of food.
The study was led by the Marine Biological Laboratory, based in Woods Hole, Mass., along with Virginia Tech; Providence College and Roger Williams University, both of Rhode Island; and California Institute of Technology. Priya’s team led computational modeling efforts, taking video of the jellyfish movements filmed in laboratory water tanks, and translating that information to computer animation.
The computer modeled jellyfish – unlike the real gelatinous zooplankton filmed in lab settings -- allows researchers to control movements of the creature however fast they wish, and in any desired direction. The virtual effort is similar to performance capture filming of actors for later computer-animated visual effects for such films as “The Lord of the Rings.”
Computer modeling was spearheaded by Colin Stewart of Charlottesville, Va., a doctoral student in Virginia Tech’s Department of Mechanical Engineering. Stewart said it was “remarkably difficult” to capture the flexibility and soft edges of the jellyfish into a full, controllable computational framework versus a more rigid body such as a shark or a human swimmer whose movements can more easily be modeled because of their joints.
Jellyfish have long been known as having a simple muscular makeup and being inefficient swimmers that rely on the current flow of water to navigate. Yet, the ability to conserve energy even while moving may help explain why jellyfish are bloom and inundate ecosystems, or even man-made systems, such as ports and dockyards.
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