Formation of Large Fluid Vortices: Corporate Merger or Hostile Takeover?

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?

Many 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 mega-corporation.

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, eyink@ams.jhu.edu
See Physics News Graphics for an example experimental image with Van Gogh-like fluid swirls