Contribution à la modélisation des processus de sédimentation : étude numérique à l'échelle de la particule

Abstract : In the present thesis, a fully-resolved numerical code has been developed for the analysis of particle-laden flows. A fictitious domain method is used. First, this numerical tool has been validated by using classical benchmarks. It has then been used to simulate the complex sedimentation of particles in three generic two-dimensional configurations: a single particle, a particle pair and a large number of particles in a confined domain. In the first case, the peak-velocity of an off-centred inclusion is recovered at low-Reynolds number. It is shown that this peak-velocity is very sensitive to fluid inertia: the peak-velocity decreases when the Reynolds number increases. This effect is delayed by the confinement. The very complex dynamics of a pair of particles sedimenting in a confined domain, observed in the litterature, is recovered (hysteresis, period-doubling cascade and chaos). It is shown that a new series of bifurcations, leading to a new attractor, emerges when the non-dimensional particle weight is increased. This new transition corresponds to a quasi-periodic route. The extended bifurcation diagram is given. The new branch discovered in this work corresponds to a nearly horizontal particle doublet, with a slow settling velocity. In the case of the settling of large number of particles, a RZ-like law is recovered for the sedimentation velocity of the fluid-particle interface. The exponent is close to 4, in contrast with the case of spheres. Finally, the sedimentation velocity at the end of the settling process is observed to be significantly reduced, like for cohesive sediments. This unexpected behaviour is related to the two-dimensionality of the suspension
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Romuald Verjus. Contribution à la modélisation des processus de sédimentation : étude numérique à l'échelle de la particule. Autre [cond-mat.other]. Université de Lorraine, 2015. Français. ⟨NNT : 2015LORR0061⟩. ⟨tel-01751693⟩

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