How giant vortices form: energy theft, researchers say
and World Science staff
Giant, energetic swirling structures—vortices—often form in situations where some fluid, whether gas or liquid, flows in an irregular or turbulent way.
But how do these things form?
Physicists have long debated the question. Researchers say they may now have an answer to shed light on these structures, such as Jupiter’s Red Spot or hurricanes and typhoons on Earth.
A new study has found that these swirling patterns arise when a larger vortex starts to swallow energy from smaller ones around it.
A research team studied the process using computer simulations, a thin layer of water, and the power of sheer calculation.
They found that the larger vortices start straining and tugging at the fluid directly around them, which changes the smaller vortices nearby. These start to stretch out horizontally, so they are no longer circular but more like ellipses. This forces them to slow them down, draining their energy. That energy goes into the larger vortices, which then become bigger and faster.
The process is known as inverse energy cascade, is “a spectacular phenomenon,” the researchers wrote in the March 3 issue of the research journal Physical Review Letters.
One theory of large-scale vortex formation has held that the large vortices eat small ones directly. But the researchers, including Shiyi Chen of Johns Hopkins University in Baltimore, Md., and colleagues, said their finding showed the large structures don’t eat the small ones—they just suck up their energy.
These results will help to model and predict formation of large-scale vortices in atmospheres and oceans, the researchers said.
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