Dispersion of particles by spontaneous interparticle percolation through unconsolidated porous media

12 pagesInternational audienceWe have performed extensive experimental and numerical studies of spontaneous percolation of small beads through an unconsolidated porous media made with large glass beads. In this paper, an experimental setup and a fast "discrete element method" algorithm are presented to deal with large numbers of particles during our interparticle percolation phenomenon studies. In all the experimental and numerical analyses, the size ratio between the moving beads and the stable packing was chosen larger than the geometrical trapping threshold: ξc=((2/(√3−1))^−1=6.464.... We measure the longitudinal and transverse dispersion coefficients versus the height of the porous medium or the number of falling small beads. The influence of bead properties such as density, diameter, or restitution coefficients was investigated by using either steel or glass beads. The individual description of these effects and their explanations were made possible by confrontation and coupling between experimental and numerical results. Indeed, with our numerical model, individual analysis of the effects of these mechanical or geometrical parameters were made possible and carried out

Transit time during the interparticle percolation process

International audienceA numerical investigation of jamming effect during the spontaneous interparticle percolation process of small beads through an unconsolidated porous media has been performed. The size ratio between the moving beads and the ones building up the porous medium was chosen larger than the geometrical trapping threshold: ξc=(2/√3−1)−1=6.464.... In this paper, we used the discrete element method algorithm to study the rebounds of particles on the top of the porous medium and the transit times of an assembly of particles through it. Several parameters such as the number of injected particles, the size ratio between beads, and the energy restitution coefficient are investigated. This study leads to give some important results of the evolution of the transit time versus the contiguous volume occupied by the percolating particles

Comportement asymptotique des structures soumises à des chargements thermo-mécaniques cycliques

Comportement asymptotique des structures soumises à des chargements thermomécaniques cycliques : application aux collecteurs d'échappementNational audienceLes structures soumises à des chargements cycliques présentent différents types de comportement asymptotique : l'adaptation, l'accommodation ou le rochet. Cette étude vise à caractériser ces différents comportements et à les identifier pour une structure soumise à des chargements thermomécaniques cycliques et dont le matériau possède des caractéristiques mécaniques variant avec la température. Les définitions proposées sont ensuite illustrées sur quelques cas simples

How discrete element method code can model dynamical phenomena such as saltation transport, multiple collision process and granular avalanches

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Mélangeur granulaire sans apport d'énergie grâce à un milieu poreux

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Transport of small particles through a 3D packing of spheres: experimental and numerical approaches

In this paper, we study the transport of particles through a porous structure. Experimentally, we focus our attention on the dependence of the mean transit time on some parameters like the number of small particles injected in the structure, and the height of the packing. We have developed a numerical model, based on a DEM method, to simulate the experiment. This model is useful for accessing the internal structure of the packing and for analysing precisely the influence of the restitution coefficient and the size ratio between spheres

2D DEM model of sand transport with wind interaction

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ETUDE DE LA GEOMETRIE DE MILIEUX GRANULAIRES MODELES TRIDIMENSIONNELS PAR SIMULATION NUMERIQUE

RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

Model of the saltation transport by Discrete Element Method coupled with wind interaction

International audienceEPJ Web of Conferences, open-access proceedings in physics and astronom

Airslide flows. Part 2--Flow modeling and comparison with experiments

International audienceAirslides are commonly used to transport dry particulate materials over distances as long as 1 km. Air is pumped through the porous bed of the transport channel to fluidize the granular material and to promote the flow down very small bed slopes. Current design of airslides is based on empirical design charts and past experiences. The present paper is the first of a two-part investigation of airslides. It reviews selected experimental studies of airslides with the goal of identifying characteristic features of these flows that we attempt to model in the numerical simulations described in the second companion paper. The experiments of Botterill and Bessant (1976) and a power-law, non-Newtonian finite element model that gave a good representation of the Botterill and Bessant (1976) velocity profiles are described. The McGill fluidized solids channel experimental setup and the associated measurements carried out by Liot (1979) and Chan (1979) are outlined. Some of these results were interpreted by means of simple, hydraulics type backwater analyses. As with the usual hydraulics type open channel flows, it was found that fully developed, uniform depth, granular airslide flows could develop. This is an important observation and it will be used as justification for the methodology employed in the calculations in the companion paper which proceeds to simulate fully developed, three-dimensional fluidized granular flows in a rectangular channel. The distinctive features identified in the review of the airslide flow experiments are summarized