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Particle motion in vortical flows
In many natural phenomena or industrial applications, heavy particles are transported in complex flows. The flow structures may happen to promote the stirring and dispersion of the particles. But the opposite can also take place and the flow configuration may contribute to the focussing and accumulation of particles within specific regions of the flow. A typical example in the natural environment is the observed patchiness of plankton concentration caused by wind-induced Langmuir cells occurring at the surface of lakes and oceans. The objective of this work is to examine the interactions of particles with local spatial structures of the flow, i.e. large vortices. We first consider the settling of particles under the action of gravity in a cellular flow field which is a simple model flow capturing key features of vortical effects on the particles. The experiment uses electroconvection to generate a two-dimensional array of controlled vortices. Experimental observations are compared to the predictions of point-particle simulations. We examine the motion of single particles (spheres and also anisotropic particles such as fibers) but also of clouds of particles to address the interplay between the multibody particle interactions and the interaction between the particles and the spatial structures of the flow. We finally consider the interactions of particles with wakes and recirculating flows around obstacles in a channel and are particularly interested in the understanding of the particle exchange between the recirculating flow regions and the free stream.
This work has been undertaken in Laboratoire IUSTI, Aix Marseille Université, CNRS, in collaboration with O. Ait Oucheggou, L. Bergougnoux, G. Bouchet, D. Lopez, B. Marchetti. The work on `Particle-laden flow around an obstacle in a pipe’ is in collaboration with V. Pointeau and G. Ricciardi, CEA Cadarache.