L'écoulement de von Kármán comme paradigme de la physique statistique hors de l'équilibre

Abstract : This dissertation tries a novel approach of statistical mechanics (at and out of equilibrium) to understand the behaviour of a fully turbulent confined flow --- von Kármán flow --- stirred by two counter-rotating impellers in a cylinder vessel. First, experimental results from speed control are extended using new PIV observations: the susceptibility divergence of the flow is studied similarly to a mean-field Ising model, for which the spatial correlations and the fluctuation-dissipation theorem are examined. Second, additional experimental results obtained in torque control are also detailed, revealing negative differential responses allowing an analogy with other out-of-equilibrium experiments such as electrical dipoles or complex fluids. These results are understood in the framework of ensemble inequivalence, typical of long-range interacting systems. In addition, escape times from attracting states in multi-stable experiments display a Kramers-like simple dynamics, as do systems with few degrees of freedom. Finally, preliminary results from the SHREK experiment are shown: torques measured in normal and superfluid liquid helium exhibit similar results. Moreover, the Reynolds number range achieved in this experiment allows a more thorough study of the evolution of the hysteresis cycle already studied for lower Reynolds numbers.
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Submitted on : Friday, November 29, 2013 - 1:24:38 PM
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  • HAL Id : tel-00911544, version 1

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Brice Saint-Michel. L'écoulement de von Kármán comme paradigme de la physique statistique hors de l'équilibre. Dynamique des Fluides [physics.flu-dyn]. Université Pierre et Marie Curie - Paris VI, 2013. Français. ⟨tel-00911544⟩

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