References of "Dorbolo, Stéphane"
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See detailEnergetic approach for the characterization of taps in granular compaction
Ludewig, François ULg; Dorbolo, Stéphane ULg; Gilet, Tristan ULg et al

in Europhysics Letters [=EPL] (2008), 84(4),

We report numerical investigations for the compaction dynamics of dense granular assemblies. The studies are based on the non-smooth contact dynamics model. Our work suggests that the dimensionless ... [more ▼]

We report numerical investigations for the compaction dynamics of dense granular assemblies. The studies are based on the non-smooth contact dynamics model. Our work suggests that the dimensionless acceleration parameter Gamma, used by a large majortiy of authors, is not appropriate for rescaling the data. We prove that the dimensionless energy Xi, injected in the granular system at lift-off, is more appropriate and leads to robust interpretations of the compaction dynamics. Indeed, the injected energy allows to pass energy barriers that separate local equilibrium states. Using the Eyring picture of relaxation dynamic, we show that the consideration of Xi leads to a new law for compaction. [less ▲]

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See detailA drop of spectroscopy
Terwagne, Denis ULg; Gilet, Tristan; Vandewalle, Nicolas ULg et al

in Physicalia Magazine (2008), 30(3), 161-168

When a low viscosity oil droplet is laid onto the surface ofa high viscosity oil liquid, it stays at rest for a moment before coalescence. The coalescence can be delayed and sometimes inlibited by ... [more ▼]

When a low viscosity oil droplet is laid onto the surface ofa high viscosity oil liquid, it stays at rest for a moment before coalescence. The coalescence can be delayed and sometimes inlibited by injecting fresh air under the droplet. This can happen when the surface ofthe bath oscillates vertically. In this case the droplet basically bounces on the interface. We obsewe that the conditions for bouncing depends on the frequency, more precisely we observe resonance when the eigenfrequency of the droplet is excited. In some conditions, a droplet presents a non axi- symmetric mode of deformation. That leads to a rotation of the droplet and to a horizontal displacement. [less ▲]

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See detailLifetime of a Bouncing Droplet
Terwagne, Denis ULg; Vandewalle, Nicolas ULg; Dorbolo, Stéphane ULg

in Physical Review E (2007), 76(5, Pt 2), 56311

When a droplet is gently laid onto the surface of the same liquid, it stays at rest for a moment before coalescence. The coalescence can be delayed and sometimes inhibited by injecting fresh air under the ... [more ▼]

When a droplet is gently laid onto the surface of the same liquid, it stays at rest for a moment before coalescence. The coalescence can be delayed and sometimes inhibited by injecting fresh air under the droplet. This can happen when the surface of the bath oscillates vertically. In this case the droplet basically bounces on the interface. The lifetime of the droplet has been studied with respect to the amplitude and the frequency of the excitation. The lifetime decreases when the acceleration increases. The thickness of the air film between the droplet and the bath has been investigated using interference fringes obtained when the system is illuminated by low-pressure sodium lamps. Moreover, both the shape evolution and the motion of the droplet center of mass have been recorded in order to evidence the phase offset between the deformation and the trajectory. A short lifetime is correlated to a small air-film thickness and to a large phase offset between the maximum of deformation and the minimum of the vertical position of the center of mass. [less ▲]

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See detailThe lifetime of bouncing droplets
Terwagne, Denis ULg; Vandewalle, Nicolas ULg; Dorbolo, Stéphane ULg

Conference (2007, October)

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See detailControlling the partial coalescence of a droplet on a vertically vibrated bath
Gilet, Tristan ULg; Vandewalle, Nicolas ULg; Dorbolo, Stéphane ULg

in Physical Review E (2007), 76(3, Pt 2), 35302

A method is proposed to stop the cascade of partial coalescences of a droplet laid on a liquid bath. The strategy consists of vibrating the bath in the vertical direction in order to keep small droplets ... [more ▼]

A method is proposed to stop the cascade of partial coalescences of a droplet laid on a liquid bath. The strategy consists of vibrating the bath in the vertical direction in order to keep small droplets bouncing. Since large droplets are not able to bounce, they partially coalesce until they reach a critical size. The system behaves as a low pass filter: droplets smaller than the critical size are selected. This size has been investigated as a function of the acceleration and the frequency of the bath vibration. Results suggest that the limit size for bouncing is related to the first mode of the droplet deformation. [less ▲]

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See detailSome aspects of electrical conduction in granular systems of various dimensions
Creyssels, Matthieu; Dorbolo, Stéphane ULg; Merlen, Alexandre et al

in European Physical Journal E -- Soft Matter (2007), 23(3), 255-264

We report on measurements of the electrical conductivity in both a 2D triangular lattice of metallic beads and in a chain of beads. The voltage/current characteristics are qualitatively similar in both ... [more ▼]

We report on measurements of the electrical conductivity in both a 2D triangular lattice of metallic beads and in a chain of beads. The voltage/current characteristics are qualitatively similar in both experiments. At low applied current, the voltage is found to increase logarithmically in good agreement with a model of widely distributed resistances in series. At high enough current, the voltage saturates due to the local welding of microcontacts between beads. The frequency dependence of the saturation voltage gives an estimate of the size of these welded microcontacts. The DC value of the saturation voltage ( similar or equal to 0.4 V per contact) gives an indirect measure of the number of welded contact carrying the current within the 2D lattice. Also, a new measurement technique provides a map of the current paths within the 2D lattice of beads. For an isotropic compression of the 2D granular medium, the current paths are localized in few discrete linear paths. This quasi-onedimensional nature of the electrical conductivity thus explains the similarity between the characteristics in the 1D and 2D systems. [less ▲]

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See detailCritical parameters for the partial coalescence of a droplet
Gilet, Tristan ULg; Mulleners, Karen; Lecomte, Jean-Paul et al

in Physical Review E (2007), 75(3, Pt 2), 36303

The partial coalescence of a droplet onto a planar liquid-liquid interface is investigated experimentally by tuning the viscosities of both liquids. The problem mainly depends on four dimensionless ... [more ▼]

The partial coalescence of a droplet onto a planar liquid-liquid interface is investigated experimentally by tuning the viscosities of both liquids. The problem mainly depends on four dimensionless parameters: The Bond number (gravity vs surface tension), the Ohnesorge numbers (viscosity in both fluids vs surface tension), and the density relative difference. The ratio between the daughter droplet size and the mother droplet size is investigated as a function of these dimensionless numbers. Global quantities such as the available surface energy of the droplet have been measured during the coalescence. The capillary waves propagation and damping are studied in detail. The relation between these waves and the partial coalescence is discussed. Additional viscous mechanisms are proposed in order to explain the asymmetric role played by both viscosities. [less ▲]

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See detailThe role of deformation in the bouncing droplet problem
Terwagne, Denis ULg; Gilet, Tristan ULg; Dorbolo, Stéphane ULg et al

Poster (2007, March)

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See detailThe role of deformation in the bouncing droplet problem
Terwagne, Denis ULg; Gilet, Tristan ULg; Dorbolo, Stéphane ULg et al

Poster (2007, February)

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See detailEffects of electromagnetic waves on the electrical properties of contacts between grains
Dorbolo, Stéphane ULg; Merlen, A.; Creyssels, M. et al

in Europhysics Letters [=EPL] (2007), 79(5),

A DC electrical current is injected through a chain of metallic beads. The electrical resistance of each bead- bead contacts is measured. At low current, the distribution of these resistances is large and ... [more ▼]

A DC electrical current is injected through a chain of metallic beads. The electrical resistance of each bead- bead contacts is measured. At low current, the distribution of these resistances is large and log- normal. At high enough current, the resistance distribution becomes sharp and Gaussian due to the creation of microweldings between some beads. The action of nearby electromagnetic waves ( sparks) on the electrical conductivity of the chain is also studied. The spark effect is to lower the resistance values of the more resistive contacts, the best conductive ones remaining unaffected by the spark production. The spark is able to induce through the chain a current enough to create microweldings between some beads. This explains why the electrical resistance of a granular medium is so sensitive to the electromagnetic waves produced in its vicinity. [less ▲]

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See detailPrecursors to avalanches in a granular monolayer
Scheller, T.; Huss, C.; Lumay, Geoffroy ULg et al

in Physical Review E (2006), 74(3, Pt 1), 31311

We investigate the stability of a granular monolayer composed of spherical grains on an inclined plate. When the tilt angle alpha increases, some reorganizations are observed throughout the pile. The ... [more ▼]

We investigate the stability of a granular monolayer composed of spherical grains on an inclined plate. When the tilt angle alpha increases, some reorganizations are observed throughout the pile. The packing fraction rho of the packing evolves by successive jumps. Those discontinuous events precede the collapse of the pile at a critical angle alphac. The occurrence of precursors before avalanches is modeled by stop-and-go motions of blocks due to the competition between sliding friction and the Janssen effect [J. Durand, (Springer-Verlag, New York, 2000)]. [less ▲]

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See detailCompaction of granular mixtures
Ludewig, François ULg; Vandewalle, Nicolas ULg; Dorbolo, Stéphane ULg

in Granular Matter (2006), 8(2), 87-91

We propose a lattice model for studying the compaction of granular mixtures under taps. Two granular species are considered: small grains with low mobilities and T-shaped grains characterized by a larger ... [more ▼]

We propose a lattice model for studying the compaction of granular mixtures under taps. Two granular species are considered: small grains with low mobilities and T-shaped grains characterized by a larger ability to move. When those grains are mixed together, the compaction dynamics is mainly controlled by the volume fraction x of the small grains. Segregation have been found on the top layers of the pile. The grain mobilities have been studied for different values of the volume fraction x. An effective grain mobility has been defined for the mixture. This mobility is given by the linear combination of the mobility of both pure species minus a non-linear interaction term. Finally, the compaction speed depends on the fraction of the anisotropic grains. [less ▲]

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See detailDancing droplets onto liquid surfaces
Vandewalle, Nicolas ULg; Terwagne, Denis ULg; Mulleners, K. et al

Poster (2006, March)

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See detailDancing droplets onto liquid surfaces
Vandewalle, Nicolas ULg; Terwagne, Denis ULg; mulleners, karin et al

in Physics of Fluids (2006), 18

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See detailDynamics of a bouncing dimer
Dorbolo, Stéphane ULg; Volfson, D.; Tsimring, L. et al

in Physical Review Letters (2005), 95(4),

We investigate the dynamics of a dimer bouncing on a vertically oscillated plate. The dimer, composed of two spheres rigidly connected by a light rod, exhibits several modes depending on initial and ... [more ▼]

We investigate the dynamics of a dimer bouncing on a vertically oscillated plate. The dimer, composed of two spheres rigidly connected by a light rod, exhibits several modes depending on initial and driving conditions. The first excited mode has a novel horizontal drift in which one end of the dimer stays on the plate during most of the cycle, while the other end bounces in phase with the plate. The speed and direction of the drift depend on the aspect ratio of the dimer. We employ event-driven simulations based on a detailed treatment of frictional interactions between the dimer and the plate in order to elucidate the nature of the transport mechanism in the drift mode. [less ▲]

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See detailStability limit of a granular monolayer
Dorbolo, Stéphane ULg

in European Physical Journal E -- Soft Matter (2005), 17(1), 77-81

A granular monolayer is composed by spherical grains on a horizontal plate. The plate is then tilted until the monolayer breaks down. This critical angle has been measured for different widths and heights ... [more ▼]

A granular monolayer is composed by spherical grains on a horizontal plate. The plate is then tilted until the monolayer breaks down. This critical angle has been measured for different widths and heights of the rectangular monolayer. The highest critical angles are found when one of these two characteristic lengths is less than about 30 bead diameters. When the polydispersity is less than one percent, the monolayer may be stable till angles close to 90 degrees. Arches induce large critical angles. On the other hand, for a large and high monolayer, the critical angle saturates towards a lower value. This angle is related to the static friction of a grain on the plate. A model based on the block dynamics is proposed to describe the behavior of the avalanche angle as a function of the size of the monolayer and the polydispersity of the beads. [less ▲]

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See detailAging of an antibubble
Dorbolo, Stéphane ULg; Reyssat, E.; Vandewalle, Nicolas ULg et al

in Europhysics Letters [=EPL] (2005), 69(6), 966-970

Antibubbles are unusual fluid objects consisting of a thin spherical air shell surrounding a liquid globule. Here we study and analyze the aging of these inverted bubbles. The lifetime is found to be ... [more ▼]

Antibubbles are unusual fluid objects consisting of a thin spherical air shell surrounding a liquid globule. Here we study and analyze the aging of these inverted bubbles. The lifetime is found to be distributed along an exponential law. Moreover, the breakdown of the air film is observed to be the analogue of dewetting by spinodal decomposition. We interpret the long lifetime of the antibubbles as resulting from the slow drainage of the air until the film reaches a critical thickness. Then, van der Waals forces act, leading to the collapse of the film. [less ▲]

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See detailBubble and granular flows: differences and similarities
Caps, Hervé ULg; Trabelsi, Samy ULg; Dorbolo, Stéphane ULg et al

in Physica A: Statistical Mechanics and its Applications (2004), 344(3-4), 424-430

We have experimentally studied the dense flow of identical bubbles below planes inclined at an angle theta. The flow is driven by the fast motion of dislocations. As a function of the density of ... [more ▼]

We have experimentally studied the dense flow of identical bubbles below planes inclined at an angle theta. The flow is driven by the fast motion of dislocations. As a function of the density of dislocations (controlled by the parameter theta), a transition occurs between a simple collective block motion and a granular-like surface flow regime. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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