Large, energetic vortex structures commonly form
in irregular or turbulent two-dimensional flows. Familiar examples
are Jupiter's Red Spot or hurricanes and typhoons on Earth. What is
the mechanism that transfers energy from small-scale vortices to
these often long-lived, large-scale circulation patterns?
suggestions have been made, such as a merger of small vortices into
larger ones. According to this scenario, the process is similar to
the consolidation or merger of many small corporations into a
In a new paper, researchers verify by experiment
and simulation a quite different mechanism based on elongation and
thinning of small-scale vortices, stretched like taffy by
large-scale strain. This process weakens the velocity of the small
vortices and transfers their kinetic energy into the large-scales.
The thinning mechanism allows the large vortices to drain the energy
of the smaller ones, squeezing them dry. Thus, the process is more
like a hostile takeover of many small corporations by a larger one
that strips their assets and liquidates them. According to the
authors, the work provides quantitative models of how a population
of small-scale vortices sustains on the large-scale circulations.
These results will help to model and predict formation of
large-scale vortices in atmospheres and oceans.
Chen et al.,
Physical Review Letters, 3 March 2006
Contact Gregory Eyink, firstname.lastname@example.org
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