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J C Ruiz-Suárez

Publications and source records attributed to J C Ruiz-Suárez.

6 recordsLinked to original sources
PubMed2005

Archimedes' principle in fluidized granular systems.

We fluidize a granular bed in a rectangular container by injecting energy through the lateral walls with high-frequency sinusoidal horizontal vibrations. In this way, the bed is brought to a steady state with no convection. We measured buoyancy forces on light spheres immersed in the bed and found that they obey Archimedes' principle. The buoyancy forces decrease when we reduce the injected energy. By measuring ascension velocities as a function of gamma, we can evaluate the frictional drag of the bed; its exponential dependence agrees very well with previous findings. Rising times of the intruders ascending through the bed were also measured, they increase monotonically as we increase the density.

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PubMed2005

Crystallization of confined non-Brownian spheres by vibrational annealing.

We introduce an experimental method to crystallize ensembles of non-Brownian spheres confined in narrow containers. The method is based on programmed vibrations and a cooling procedure (annealing). Starting with a granular gas, the system slowly relaxes into a solid ordered structure: Body-centered-tetragonal and face-centered-cubic single crystals are obtained depending on the dimensions of the capillaries. Dry and lubricated beads behave differently, indicating that a sticking coefficient between the particles is important in the dynamics of the crystallization.

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PubMed2004

Vibration-induced granular segregation: a phenomenon driven by three mechanisms.

The segregation of large spheres in a granular bed under vertical vibrations is studied. In our experiments, we systematically measure rise times as a function of density, diameter, and depth, for two different sinusoidal excitations. The measurements reveal that, at low frequencies, inertia and convection are the only mechanisms behind segregation. Inertia (convection) dominates when the relative density is greater (less) than one. At high frequencies, where convection is suppressed, fluidization of the granular bed causes either buoyancy or sinkage and segregation occurs.

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PubMed2003

Inertia in the Brazil nut problem.

The rise dynamics of a large particle, in a granular bed under vertical vibrations, is experimentally studied with an inductive device designed to track the particle while it climbs through the granulate under different conditions. A model based on energy considerations is presented to explain our experimental data, drawing the important conclusion that it is the inertia of the particle, assisted by Reynolds dilatancy, the driven force behind its ascension mechanism. The ascension reveals a friction profile within the column which remains unchanged for different accelerations.

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PubMed2002

Epitaxial growth of granular single crystals.

Compaction from a random-loose-packed to a random-close-packed phase is observed when monodisperse granular beds are shaken, but beyond this packing, the system freezes up in a jammed structure. Here we report a technique to grow large hard-sphere granular crystals, with perfect stacking and no defects by means of a "gas phase" epitaxial procedure. We study the growth mechanism and provide evidence that the observed granular crystallization is driven by gravity and energy dissipation.

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