The pirouette effect in the chaos of turbulence
(PhysOrg.com) -- The quick mixing of coffee and milk after stirring or the formation of raindrops in clouds: these are just two of many phenomena in which turbulent flows play a decisive role. Researchers at the Max Planck Institute for Dynamics and Self-Organization and the Ecole Normale Superieure de Lyon have now discovered that the seemingly random turbulent flows actually have an astonishingly uniform structure. According to the findings, vortices are a basic ingredient of turbulent flows and they behave similarly to an ice-skater performing a pirouette a technique whereby the skater bends his or her arms to increase the speed of rotation. The researchers monitored this pirouette effect in vortices of various sizes in a turbulent liquid. In doing so, they unravelled a mystery that has confounded turbulence researchers for decades namely the question of how energy flows from large to ever-smaller vortices, and how it is...