6. Turbulent Thermal Convection and Emergence of Isolated Large Single Vortices in Soap Bubbles

Experiments using a novel thermal convection cell consisting of half a soap bubble heated at the equator to study turbulent thermal convection and the movement of isolated vortices are reviewed. The soap bubble, subject to stratification, develops thermal convection at its equator. A particular feature of this cell is the emergence of isolated vortices. These vortices resemble hurricanes or cyclones and similarities between these structures and their natural counterparts are found. This is brought forth through a study of the mean square displacement of these objects showing signs of superdiffusion. In addition to these features, the study of the statistical properties of the turbulence engendered in these soap bubbles shows a clear indication for the existence of the so-called Bolgiano–Obukhov scaling both for the temperature and the velocity fluctuations. A remarkable transition is uncovered: the temperature and the velocity structure functions show intermittency for small temperature gradients; this intermittency then disappears for large gradients.