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Paris, April 4, 2008

Better understanding hurricane trajectories, thanks to soap bubbles

Researchers at the Centre de Physique Moléculaire Optique et Hertzienne (CPMOH) (CNRS/Université Bordeaux 1) and the Université de la Réunion(1) have discovered that vortices created in soap bubbles behave like real cyclones and hurricanes in the atmosphere. Soap bubbles have enabled the researchers to characterize for the first time the random factor that governs the movement and paths of vortices. These results, published on the 7 April 2008 on the website of the journal Physical Review Letters, could lead to a better understanding of such increasingly common and often devastating atmospheric phenomena.

A soap bubble is an ideal model for studying the atmosphere because it has analogous physical properties and, like the atmosphere, it is composed of a very thin film in relation to its diameter(2). In this experiment, the researchers created a half soap bubble that they heated at the “equator” and then cooled at the “poles”, thereby creating a single large vortex, similar to a hurricane, in the wall of the bubble. The researchers studied the movement of this vortex, which fluctuates in a random manner. This is characterized by a law known as a superdiffusive law(3), well known to physicists, but which had not until then been observed in the case of single vortices in a turbulent environment.

The disconcerting resemblance between vortices on soap bubbles and cyclones led the researchers to study their similarities. By analyzing in detail the trajectories of certain recent hurricanes such as Ivan, Jane, Nicholas, etc., the researchers measured the random factor that is always present in the movement of hurricanes. They then demonstrated the remarkable similarity of these fluctuations with those that characterize the disordered movement of the vortices that they created on soap bubbles(4)

Taking this random factor into account in predicting the trajectory of hurricanes will be useful in anticipating the probability of impact on a given site or locality. Although the mean trajectory of hurricanes (without any fluctuations) is beginning to be well simulated by meteorologists, this random factor has, until now, been poorly understood. This discovery highlights a universality in the statistics of trajectory fluctuations and should make it possible in the future to better predict the behavior of hurricanes and anticipate the risks.

Bulles de savon 1

© American Physical Society (APS) (This image is available from the CNRS photograph library, phototheque@cnrs-bellevue.fr)

Image 1 – Thermal convection bubble with a large vortex in the upper part of the image.




Bulles de savon 2

© American Physical Society (APS) (This image is available from the CNRS photograph library, phototheque@cnrs-bellevue.fr)

Image 2 – Four photos of a single vortex as it emerges, expands and shifts.




Notes:

1) Laboratoire de Génie Industriel.
2) The skin or film of soap is only several microns thick whereas the diameter of the bubble is around ten centimeters.
3) Law corresponding to a “Levy flight” random type movement, in other words a type of random walk dominated by several jumps of limited number but of large amplitude.
4) With a similar superdiffusive law.

References:

Thermal convection and emergence of isolated vortices in soap bubbles, F. Seychelles, Y. Amarouchene, M. Bessafi*, and H. Kellay Université Bordeaux 1, CPMOH UMR 5798 du CNRS and * Université de la Réunion, Lab. de Génie Industriel.

Contact information:

Researcher
Hamid Kellay
T 05 40 00 65 11
h.kellay@cpmoh.u-bordeaux1.fr

Public Information Officer
Laetitia Louis
T 01 44 96 51 37
Laetitia.louis@cnrs-dir.fr


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