OSAKA - Researchers at a Japanese university used supercomputer simulations to find that dolphins produce large, powerful vortices by flapping their tails up and down to swim quickly, raising hopes of developing underwater robots that can move swiftly while using little energy.
A 2006 study by U.S. researchers found that dolphins can swim at speeds of up to 30 kilometers per hour. But efforts to uncover the mechanism behind this ability were hindered by the turbulence generated by the dolphins' large tail movements, which disrupted the velocity and direction of the surrounding water.
In the study, a team of researchers from the University of Osaka used the Fugaku supercomputer to calculate the force that dolphins' tails exert on the surrounding water when they flap up and down, using the information to precisely simulate the resulting turbulence.
After analyzing the simulations, the researchers discovered that large, strong vortex rings, roughly the size of a dolphin's tail, propelled the mammals forward by pushing water backward.
The large vortices created numerous smaller ones, but they contributed little to the dolphin's forward motion, the study said.
The findings were recently published in Physical Review Fluids and selected as an Editors' Suggestion.
"The largest vortices are responsible for most of the propulsion," said Yutaro Motoori, lead author of the study.
He expressed hope that designs capable of producing vortices that efficiently generate thrust could improve the performance of underwater robots and drones.
