References of "Caps, Hervé"
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See detailBlock-to-granular-like transition in dense bubble flows
Vandewalle, Nicolas ULg; Trabelsi, Samy ULg; Caps, Hervé ULg

in Europhysics Letters [=EPL] (2004), 65(3), 316-322

We have experimentally investigated 2-dimensional dense bubble flows underneath inclined planes. Velocity profiles and velocity fluctuations have been measured. A broad second-order phase transition ... [more ▼]

We have experimentally investigated 2-dimensional dense bubble flows underneath inclined planes. Velocity profiles and velocity fluctuations have been measured. A broad second-order phase transition between two dynamical regimes is observed as a function of the tilt angle theta. For low theta values, a block motion is observed. For high theta values, the velocity pro. le becomes curved and a shear velocity gradient appears in the flow. [less ▲]

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See detailGranular size segregation in underwater sand ripples
Rousseaux, G.; Caps, Hervé ULg; Wesfreid, J. E.

in European Physical Journal E -- Soft Matter (2004), 13(2), 213-219

We report an experimental study of a binary sand bed under an oscillating water flow. The formation and evolution of ripples is observed. The appearance of a granular segregation is shown to strongly ... [more ▼]

We report an experimental study of a binary sand bed under an oscillating water flow. The formation and evolution of ripples is observed. The appearance of a granular segregation is shown to strongly depend on the sand bed preparation. The initial wavelength of the mixture is measured. In the final steady state, a segregation in volume is observed instead of a segregation at the surface as reported before. The correlation between this phenomenon and the fluid flow is emphasised. Finally, different "exotic" patterns and their geophysical implications are presented. [less ▲]

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See detailFluid instabilities in the birth and death of antibubbles
Dorbolo, Stéphane ULg; Caps, Hervé ULg; Vandewalle, Nicolas ULg

in New Journal of Physics (2003), 5

Antibubbles have been produced and studied with the help of a high-speed camera. An antibubble is defined as a fluid object constituted by a thin air shell surrounding a liquid and surrounded by the same ... [more ▼]

Antibubbles have been produced and studied with the help of a high-speed camera. An antibubble is defined as a fluid object constituted by a thin air shell surrounding a liquid and surrounded by the same liquid. Images reveal some key physical processes and fluid instabilities which take place when an antibubble forms and dies. The collapsing speed of the air film has been measured. Culik's theory does not apply. A new mechanism has been introduced. [less ▲]

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See detailGranular spirals on erodible sand bed submitted to a circular fluid motion
Caps, Hervé ULg; Vandewalle, Nicolas ULg

in Physical Review E (2003), 68(3, Pt 1), 31303

An experimental study of a granular surface submitted to a circular fluid motion is presented. The appearance of an instability along the sand-water interface is observed beyond a critical radius r(c ... [more ▼]

An experimental study of a granular surface submitted to a circular fluid motion is presented. The appearance of an instability along the sand-water interface is observed beyond a critical radius r(c). This creates ripples with a spiral shape on the granular surface. A phase diagram of such patterns is constructed and discussed as a function of the rotation speed omega of the flow and as a function of the height of water h above the surface. The study of r(c) as a function of h, omega, and r parameters is reported. Thereafter, r(c) is shown to depend on the rotation speed according to a power law. The ripple wavelength is found to decrease when the rotation speed increases and is proportional to the radial distance r. The azimuthal angle epsilon of the spiral arms is studied. It is found that epsilon scales with homegar. This lead to the conclusion that epsilon depends on the fluid momentum. Comparison with experiments performed with fluids allows us to state that the spiral patterns are not the signature of an instability of the boundary layer. [less ▲]

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See detailLong lasting instabilities in granular mixtures
Caps, Hervé ULg; Michel, Renaud; Lecocq, N. et al

in Physica A: Statistical Mechanics and its Applications (2003), 326(3-4), 313-321

We have performed experiments of axial segregation in the Oyama's drum. We have tested binary granular mixtures during very long times. The segregation patterns have been captured by a CCD camera and ... [more ▼]

We have performed experiments of axial segregation in the Oyama's drum. We have tested binary granular mixtures during very long times. The segregation patterns have been captured by a CCD camera and spatio-temporal graphs are created. We report the occurrence of instabilities which can last several hours! We stress that those instabilities originate from the competition between axial and radial segregations. We put into evidence the occurrence of giant fluctuations in the fraction of grain species along the surface during the unstable periods. (C) 2003 Elsevier B.V. All rights reserved. [less ▲]

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See detailFoam imbibition in microgravity - An experimental study
Caps, Hervé ULg; Decauwer, H.; Chevalier, M. L. et al

in European Physical Journal B -- Condensed Matter (2003), 33(1), 115-119

We report an experimental study of aqueous foam imbibition in microgravity with strict mass conservation. The foam is in a Hele-Shaw cell. The bubble edge width l is measured by image analysis. The ... [more ▼]

We report an experimental study of aqueous foam imbibition in microgravity with strict mass conservation. The foam is in a Hele-Shaw cell. The bubble edge width l is measured by image analysis. The penetration of the liquid in the foam, the foam imbibition, the foam inflation, and the rigidity loss are shown all to obey strict diffusion processes. The motion of bubbles needed for the foam inflation is a slow two-dimensional process with respect to the one-dimensional capillary rise of liquid. The foam is found to imbibes faster than it inflates. [less ▲]

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See detailA Modified Tetris Model Including The Effect of Friction
Ludewig, François ULg; Dorbolo, Stéphane ULg; Caps, Hervé ULg et al

in Traffic and Granular Flow'03 (2003)

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See detailCascades of popping bubbles
Vandewalle, Nicolas ULg; Caps, Hervé ULg; Dorbolo, Stéphane ULg

in Physica A: Statistical Mechanics and its Applications (2002), 314(1-4), 320-324

We study the intermittent dynamics of collapsing foams. Avalanches of popping bubbles are observed. Although correlations between successive popping bubbles are emphasized, film raptures at the air/foam ... [more ▼]

We study the intermittent dynamics of collapsing foams. Avalanches of popping bubbles are observed. Although correlations between successive popping bubbles are emphasized, film raptures at the air/foam interface seem to be independent of the bubble size. Possible mechanisms for cascades of bubble pops are proposed and discussed. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailPatterns in hydraulic ripples with binary granular mixtures
Caps, Hervé ULg; Vandewalle, Nicolas ULg

in Physica A: Statistical Mechanics and its Applications (2002), 313(3-4), 357-364

An experimental study of a binary granular mixture submitted to a transient shear flow in a cylindrical container is reported. The formation of ripples with a spiral shape is observed. The appearance of ... [more ▼]

An experimental study of a binary granular mixture submitted to a transient shear flow in a cylindrical container is reported. The formation of ripples with a spiral shape is observed. The appearance of phase segregation in those spiral patterns is shown. The relative grain size between sand species is found to be a relevant parameter leading to phase segregation. However, the relative repose angle is an irrelevant parameter. The formation of sedimentary structures is also presented. They result from a ripple climbing process. The "sub-critical" or "super-critical" character of the lamination patterns is shown to depend on the rotation speed of the container. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailLabyrinthine Granular Landscapes
Caps, Hervé ULg; Vandewalle, Nicolas ULg

in Physical Review. E : Statistical, Nonlinear, and Soft Matter Physics (2001), 64(5, Pt 1), 52301

We have numerically studied a model of granular landscape eroded by wind. We show the appearance of labyrinthic patterns when the wind orientation turns by 90 degrees. The occurrence of such structures is ... [more ▼]

We have numerically studied a model of granular landscape eroded by wind. We show the appearance of labyrinthic patterns when the wind orientation turns by 90 degrees. The occurrence of such structures is discussed. Moreover, we introduce the density n(k) of "defects" as the dynamic parameter governing the landscape evolution. A power-law behavior of n(k) is found as a function of time. In the case of wind variations, the exponent (drastically) shifts from two to one. The presence of two asymptotic values of n(k) implies the irreversibility of the labyrinthic formation process. [less ▲]

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See detailRipple and Kink Dynamics
Caps, Hervé ULg; Vandewalle, Nicolas ULg

in Physical Review. E : Statistical, Nonlinear, and Soft Matter Physics (2001), 64(4, Pt 1), 41302

We propose a relevant modification of the Nishimori-Ouchi model [Phys. Rev. Lett. 71, 197 (1993)] for granular landscape erosion. We explicitly introduce an additional parameter: the angle of repose ... [more ▼]

We propose a relevant modification of the Nishimori-Ouchi model [Phys. Rev. Lett. 71, 197 (1993)] for granular landscape erosion. We explicitly introduce an additional parameter: the angle of repose straight theta(r), and an additional process: avalanches. We show that the straight theta(r) parameter leads to an asymmetry of the ripples, as observed in natural patterns. The temporal evolution of the maximum ripple height h(max) is limited and not linear according to recent observations. The ripple symmetry and the kink dynamics are studied and discussed. [less ▲]

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