Maza-Ozcoidi, D. (Diego)
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- Influence of the feeding mechanism on deposits of square particles(2013) Pagonabarraga, I. (Ignacio); Zuriguel-Ballaz, I. (Iker); Cruz-Hidalgo, R. (Raúl); Acevedo-Escalante, M. (Manuel Francisco); Maza-Ozcoidi, D. (Diego)In a previous paper [Hidalgo et al., Phys. Rev. Lett. 103, 118001 (2009)] it was shown that square particles deposited in a silo tend to align with a diagonal parallel to the gravity, giving rise to a deposit with very particular properties. Here we explore, both experimentally and numerically, the effect on these properties of the filling mechanism. In particular, we modify the volume fraction of the initial configuration from which the grains are deposited. Starting from a very dilute case, increasing the volume fraction results in an enhancement of the disorder in the final deposit characterized by a decrease of the final packing fraction and a reduction of the number of particles oriented with their diagonal in the direction of gravity. However, for very high initial volume fractions, the final packing fraction increases again. This result implies that two deposits with the same final packing fraction can be obtained from very different initial conditions. The structural properties of such deposits are analyzed, revealing that, although the final volume fraction is the same, their micromechanical properties notably differ.
- Clogging and unclogging of many-particle systems passing through a bottleneck(EDP Sciences, 2017) Zuriguel-Ballaz, I. (Iker); Arevalo, R. (Roberto); Maza-Ozcoidi, D. (Diego); Janda, A. (Álvaro); Montero, Á. (Ángel)When a group of discrete particles pass through a narrowing, the flow may become arrested due to the development of structures that span over the size of the aperture. Then, it is said that the system is clogged. Here, we will discuss about the existence of a phase diagram for the clogged state that has been recently proposed, arguing on its usefulness to describe different systems of discrete bodies ranging from granular materials, to colloidal suspensions and live beings. This diagram is built based on the value of a flowing parameter which characterizes the intermittent flow observed in all these discrete systems provided that there is an external or internal energy supply. Such requirement, which is necessary to destabilize the clogging arches, is absent in a standard static silo, which is therefore examined as a particular case. This view will help to understand some a priori inconsistencies concerning the role of driving force in the clogging process that have been found in the last years.
- Experimental phase synchronization of chaotic convective flows(American Physical Society, 2000) Boccaletti, S. (S.); Maza-Ozcoidi, D. (Diego); Vallone, A.F. (A. F.); Mancini-Maza, H. L. (Hector Luis)We report experimental evidence of phase synchronization of high dimensional chaotic oscillators in a laboratory experiment. The experiment consists of a thermocapillary driven convective cell in a time dependent chaotic regime. The synchronized states emerge as a consequence of a localized temperature perturbation to the heater. The transition to phase synchronization is studied as a function of the external perturbations. The existence and stability conditions for this phenomenon are discussed.
- Stress transmission in systems of faceted particles in a silo: the roles of filling rate and particle aspect ratio(Springer, 2014) Pagonabarraga, I. (Ignacio); Zuriguel-Ballaz, I. (Iker); Cruz-Hidalgo, R. (Raúl); Alonso-Marroquin, F. (F.); Acevedo-Escalante, M. (Manuel Francisco); Maza-Ozcoidi, D. (Diego)We present experimental and numerical results for particle alignment and stress distribution in packings of faceted particles deposited in a small-scale bi-dimensional silo. First, we experimentally characterize the deposits’ morphology in terms of the particles’ aspect ratio and feeding rate. Then we use the experimental results to validate our discrete element method (DEM) based on spheropolygons. After achieving excellent agreement, we use contact forces and fabric provided by the simulations to calculate the coarse-grained stress tensor. For low feeding rates, square particles display a strong tendency to align downwards, i.e., with a diagonal parallel to gravity. This morphology leads to stress transmission towards the walls, implying a quick development of pressure saturation, in agreement with the Janssen effect. When the feed rate is increased, both the disorder and the number of horizontal squares in the silo increase, hindering the Janssen effect. Conversely, for elongated particles the feed rate has a weak effect on the final deposit properties. Indeed, we always observe highly ordered structures of horizontal rods where the stress is transmitted mainly in the vertical direction.
- Twisting, an alternative strategy to compact granular materials(EDP Sciences, 2017) Zuriguel-Ballaz, I. (Iker); Maza-Ozcoidi, D. (Diego); Asencio, K. (Karol)Nowadays, the common method to pack granular materials is to tap the ensemble against the gravity. Despite the apparent simplicity of that method, the asymptotic states reached by the tapped systems have strongly dependences on parameters like the shape of the tapping pulse, the container geometry or the ratio between lateral and axial dimensions. Beyond the restrictions imposed by the system boundaries, the particle shape (like rods or tetrahedrons) plays a central role in the evolution and the final state of the ensemble. In this work, we introduce an unconventional method for compacting granular ensembles by applying a sequence of alternating counterrotating pulses or ¿twists¿. By using spherical particles we analyze the efficiency of this method to achieve highly packed configurations.
- Contact network topology in tapped granular media(2013) Pugnaloni, L.A. (Luis A.); Zuriguel-Ballaz, I. (Iker); Arevalo, R. (Roberto); Maza-Ozcoidi, D. (Diego)We analyze the contact network of simulated two-dimensional granular packings in different states of mechanical equilibrium obtained by tapping. We show that topological descriptors of the contact network allow one to distinguish steady states of the same mean density obtained with different tap intensities. These equal-density states were recently proven to be distinguishable through the mean force moment tensor. In contrast, geometrical descriptors, such as radial distribution functions, bond order parameters, and Voronoi cell distributions, can hardly discriminate among these states. We find that small-order loops of contacts—the polygons of the network—are especially sensitive probes for the contact structure.
- Decoupling Geometrical and Kinematic Contributions to the Silo Clogging Process(2018) Zuriguel-Ballaz, I. (Iker); Maza-Ozcoidi, D. (Diego); Gella, D. (Diego)Based on the implementation of a novel silo discharge procedure, we are able to control the grains velocities regardless of the outlet size. This allows isolating the geometrical and kinematic contributions to the clogging process. We find that, for a given outlet size, reducing the grains velocities to extremely low values leads to a clogging probability increment of almost two orders of magnitude, hence revealing the importance of particle kinematics in the silo clogging process. Then, we explore the contribution of both variables, outlet size and grains velocity, and we find that our results agree with an already known exponential expression that relates clogging probability with outlet size. We propose a modification of such expression revealing that only two parameters are necessary to fit all the data: one is related with the geometry of the problem, and the other with the grains kinematics.
- Phase Clustering and Collective Behaviors in Globally Coupled Map Lattices due to mean Filed Effects(2000) Boccaletti, S. (S.); Maza-Ozcoidi, D. (Diego); Mancini-Maza, H. L. (Hector Luis)We describe the emergence of phase clustering and collective behaviors in an ensemble of chaotic coupled map lattices, due to a mean eld interaction. This kind of interaction is responsible for the appearence of a collective state, wherein the mean eld evolution of each lattice undergoes a periodic behavior in space. We analyze the transition to such a state in an ensemble of one-dimensional lattices of logistic maps, showing that the resulting behavior cooperatively maximizes the energy of the mean eld activity.
- Experimental proof of faster-is-slower in systems of frictional particles flowing through constrictions(2015) Pugnaloni, L.A. (Luis A.); Parisi, D.R. (D. R.); Zuriguel-Ballaz, I. (Iker); Peralta, J.P. (Juan Pablo); Martín-Gómez, C. (César); Pastor-Gutierrez, J.M. (José Martín); Ferrer, L.M. (Luis Miguel); Maza-Ozcoidi, D. (Diego); Montero, Á. (Ángel); Gago, P.A. (Paula A.)The “faster-is-slower” (FIS) effect was first predicted by computer simulations of the egress of pedestrians through a narrow exit [D. Helbing, I. J. Farkas, and T. Vicsek, Nature (London) 407, 487 (2000)]. FIS refers to the finding that, under certain conditions, an excess of the individuals’ vigor in the attempt to exit causes a decrease in the flow rate. In general, this effect is identified by the appearance of a minimum when plotting the total evacuation time of a crowd as a function of the pedestrian desired velocity. Here, we experimentally show that the FIS effect indeed occurs in three different systems of discrete particles flowing through a constriction: (a) humans evacuating a room, (b) a herd of sheep entering a barn, and (c) grains flowing out a 2D hopper over a vibrated incline. This finding suggests that FIS is a universal phenomenon for active matter passing through a narrowing.
- Role of driving force on the clogging of inert particles in a bottleneck(2014) Zuriguel-Ballaz, I. (Iker); Arevalo, R. (Roberto); Maza-Ozcoidi, D. (Diego); Montero, Á. (Ángel)