  Etude de grains et de matière granulaire sous champs électriquesMersch, Eric  Doctoral thesis (2013) Electric fields have been used to modify properties of dilute and dense granular materials. For the dilute case, we showed that electric fields can be used to inject kinetic energy on the material. We ... [more ▼] Electric fields have been used to modify properties of dilute and dense granular materials. For the dilute case, we showed that electric fields can be used to inject kinetic energy on the material. We studied the dynamics of a single bead, two beads and three beads systems. The dynamics is described by a mathematical model which is in quantitative agreement with experiments. A synchronization effect is observed and it is described by a phase coupled oscillators model. We also show that electric fields can be used to tune the cohesion of dense granular media. A transition of the geometry of the flow is observed. Intermittences are induced by the electric field. [less ▲] Detailed reference viewed: 38 (13 ULg) Symmetry breaking in a few-body system with magnetocapillary interactionsVandewalle, Nicolas ; ; et alin Physical Review. E : Statistical, Nonlinear, and Soft Matter Physics (2012), 85 We have experimentally investigated the interactions between floating magnetic spheres which are submitted to a vertical magnetic field, ensuring a tunable repulsion, while capillary forces induce ... [more ▼] We have experimentally investigated the interactions between floating magnetic spheres which are submitted to a vertical magnetic field, ensuring a tunable repulsion, while capillary forces induce attraction. We emphasize the complex arrangements of floating bodies. The equilibrium distance between particles exhibits hysteresis when the applied magnetic field is modified. Irreversible processes are evidenced. Symmetry breaking is also found for three identical floating bodies when the strength of the magnetic repulsion is tuned. We propose a Dejarguin-Landau-Verwey-Overbeek (DLVO)–like potential, i.e., an interaction potential with a primary and a secondary minimum, capturing the main physical features of the magnetocapillary interaction, which is relevant for self-assembly. [less ▲] Detailed reference viewed: 58 (21 ULg)Antiphase synchronization of electrically shaken conducting beadsMersch, Eric ; Vandewalle, Nicolas in Physical Review. E : Statistical, Nonlinear, and Soft Matter Physics (2011), 84 Detailed reference viewed: 22 (5 ULg) Hysteretic behavior in three-dimensional soap film rearrangementsVandewalle, Nicolas ; ; Schockmel, Julien et alin Physical Review. E : Statistical, Nonlinear, and Soft Matter Physics (2011), 83 Detailed reference viewed: 85 (49 ULg)Effect of an electric field on an intermittent granular flowMersch, Eric ; Lumay, Geoffroy ; Boschini, Frédéric et alin Physical Review. E : Statistical, Nonlinear, and Soft Matter Physics (2010), 81 Granular gravity driven flows of glass beads have been observed in a silo with a flat bottom. A dc high electric field has been applied perpendicularly to the silo to tune the cohesion. The outlet mass flow ... [more ▼] Granular gravity driven flows of glass beads have been observed in a silo with a flat bottom. A dc high electric field has been applied perpendicularly to the silo to tune the cohesion. The outlet mass flow has been measured. An image subtraction technique has been applied to visualize the flow geometry and a spatiotemporal analysis of the flow dynamics has been performed. The outlet mass flow is independent of voltage, but a transition from funnel flow to rathole flow is observed. This transition is of probabilistic nature and an intermediate situation exists between the funnel and the rathole situations. At a given voltage, two kinds of flow dynamics can occur: a continuous flow or an intermittent flow. The electric field increases the probability to observe an intermittent flow. [less ▲] Detailed reference viewed: 28 (8 ULg) |
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