Publications de Lionel Pournin

Weakly regular subdivisions

It is shown that 2-dimensional subdivisions can be made regular by moving their vertices within parallel 1-dimensional spaces. As a consequence, any 2-dimensional subdivision is projected from the boundary complex of a 4-polytope. ...

Springer-Verlag2012

A result on flip-graph connectivity

Lionel Pournin

A polyhedral subdivision of a d-dimensional point configuration A is k-regular if it is projected from the boundary complex of a polytope with dimension at most d+k. Call γk(A) the subgraph induced by k-regular triangulations in the flip-graph of A. Gel’fa ...

Walter de Gruyter2012

Particle shape versus friction in granular jamming

Michel Tsukahara, Thomas Liebling, Lionel Pournin

What is the influence of sand grain shapes on an hourglass accuracy, and how does it affect the jamming probability? We study such a question using numerical simulation and our recently introduced spheropolyhedral particles. Spheropolyhedra constitute a ve ...

AIP2009

Simple probabilistic modeling of granular jamming and validation using DEM

Michel Tsukahara, Thomas Liebling, Lionel Pournin

We study the flow of grains in a bi-dimensional hopper. We propose a simple continuous probabilistic flow model: from uniformly random positions in the hopper, particles evolve without interaction towards the hopper aperture and jamming occurs if sufficien ...

AIP2009

Coupled tomography and distinct-element-method approach to exploring the granular media microstructure in a jamming hourglass

Michel Tsukahara, Thomas Liebling, Giorgio Margaritondo, Michaël Unser, Daniel Sage, Lionel Pournin, Marco Ramaioli, Vincent Gajdosik, Slobodan Mitrovic

We describe an approach for exploring microscopic properties of granular media that couples x-ray microtomography and distinct-element-method (DEM) simulations through image analysis. We illustrate it via the study of the intriguing phenomenon of instant a ...

APS2008

Constrained paths in the flip-graph of regular triangulations

Thomas Liebling, Lionel Pournin

We describe particular paths in the flip-graph of regular triangulations in any dimension. It is shown that any pair of regular triangulations is connected by a path along which none of their common faces are destroyed. As a consequence, we obtain the conn ...

2007

Vertical ordering of rods under vertical vibration

Thomas Liebling, Lionel Pournin, Marco Ramaioli

Granular media composed of elongated particles rearrange and order vertically upon vertical vibration. We perform pseudo-two-dimensional discrete element model simulations and show that this phenomenon takes place also with no help from vertical walls. We ...

2007

About the influence of friction and polydispersity on the jamming behavior of bead assemblies

Thomas Liebling, Lionel Pournin, Marco Ramaioli

We study the jamming of bead assemblies placed in a cylindrical container whose bottom is pierced with a circular hole. Their jamming behavior is quantified here by the mean critical diameter, that is the diameter of the hole for which the jamming probabil ...

EDP Sciences, Springer2007

Three-dimensional distinct element simulation of spherocylinder crystallization

Michel Tsukahara, Jean-Albert Ferrez, Thomas Liebling, Lionel Pournin, Marco Ramaioli

We present a three-dimensional distinct element model (DEM) able to handle populations of spherocylinders. We report on granular crystallization occurring when vibrating mono-disperse assemblies of spherocylinders that faithfully reproduce the correspondin ...

Springer-Verlag2005

A generalization of distinct element method to tridimensional particles with complex shapes

Thomas Liebling, Lionel Pournin

The distinct element method was originally designed to handle spherical particles. Here, this method is generalized to a wider range of particle shapes called spherosimplices. A contact detection method is given as well which uses weighted Delaunay triangu ...

A.A.Balkema Publishers2005

On the behavior of spherical and non-spherical grain assemblies, its modeling and numerical simulation

Lionel Pournin

This thesis deals with the numerical modeling and simulation of granular media with large populations of non-spherical particles. Granular media are highly pervasive in nature and play an important role in technology. They are present in fields as diverse ...

EPFL2005

Numerical and experimental investigation of alignment and segregation of vibrated granular media composed of rods and spheres

Thomas Liebling, Lionel Pournin, Marco Ramaioli

Homogenous granular media composed of spherocylindrical rods rearrange and order vertically upon vibration. Performing pseudo-bidimensional experiments and simulations, we isolated void-filling mechanism as a cause for this phenomenon, independently of wal ...

A.A.Balkema Publishers2005