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Chaotic mixing by rod-stirring devices in open and closed flows

Abstract : We have studied the mixing of viscous fluids in 2-D closed and open flows, where stirring rods create chaotic advection, i.e. complex Lagrangian trajectories. Our study, experimental, numerical and theoretical, is based on two types of chaotic mixing experiments, in a closed vat and in an open channel. For closed flows, we have first proposed a topological description of mixing by the entanglement of periodic orbits that we called "ghost rods". The experimental study of the concentration field of a dye has then revealed the role of the walls of the domain where mixing takes place, in closed and open flows as well. For closed flows, the chaotic or regular nature of trajectories initialized close to the wall determines the evolution of the concentration field, even far from the walls. In particular, we have observed slow (algebraic) dynamics of homogenization when the chaotic region extends to no-slip walls. In open flows, we have reported on the evolution of the concentration field in the mixing and downstream regions, resulting from the injection of a dye blob. We have described the poorly mixed elements that escape quickly, as well as the asymptotic onset of a permanent (self-similar) pattern determined by the periodic orbits inside the mixing region. Finally, various models derived from the baker's map have allowed us to understand most observed mechanisms.
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Contributor : Emmanuelle Gouillart <>
Submitted on : Saturday, January 12, 2008 - 11:14:35 AM
Last modification on : Monday, October 19, 2020 - 11:11:37 AM
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  • HAL Id : tel-00204109, version 1

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Emmanuelle Gouillart. Chaotic mixing by rod-stirring devices in open and closed flows. Fluid Dynamics [physics.flu-dyn]. Université Pierre et Marie Curie - Paris VI, 2007. English. ⟨tel-00204109⟩

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