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Transport and Density Fluctuations in Disordered Systems: Appliations to Atmospheric Dispersion

Abstract : The turbulent transport of particles is an important phenomena which appears in many natural and industrial processes. Understanding its properties, and, in particular, the creation of strong density fluctuations, is fundamental to improve models and refine forecasts. This can lead to significant benefits in issues related to economics, the environmental and health. A Lagrangian study of the tracer pair separation was carried out with the help of high resolution data analysis. This allowed us to point out the weaknesses of the mean-field approaches on which most models are based. For the separation, it is found that the transition from the regime of Batchelor (or ballistic) to that of Richardson (or explosive) occurs at times given by those typical of the turbulent kinetic energy dissipation. It is also found that Richardson's law can be reinterpreted in terms of diffusive behaviour of the velocity differences. Phenomenological arguments allow us to explain this effect through the decorrelation of the acceleration differences and the stationarity of the kinetic energy transfer ratio at large times. The high-order moments of both separation and velocity are also investigated to address the question of "violent events" in the distribution of the distances. Finally, a one-dimensional mass ejection model is proposed and used to examine the density fluctuations of heavy particles transported by the random environment.
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https://tel.archives-ouvertes.fr/tel-00944511
Contributor : Rehab Bitane <>
Submitted on : Monday, February 10, 2014 - 4:50:54 PM
Last modification on : Wednesday, October 14, 2020 - 4:22:59 AM
Long-term archiving on: : Sunday, May 11, 2014 - 6:30:11 AM

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  • HAL Id : tel-00944511, version 1

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Rehab Bitane. Transport and Density Fluctuations in Disordered Systems: Appliations to Atmospheric Dispersion. Mechanics of the fluids [physics.class-ph]. Université Nice Sophia Antipolis, 2012. English. ⟨tel-00944511⟩

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