Humidity-Induced Cohesion Effects in Granular Media

2000 ◽  
Vol 627 ◽  
Author(s):  
Nathalie Fraysse ◽  
Luc Petit
Keyword(s):  
Granular Medium ◽  
Granular Media ◽  
Global Scale ◽  
Interparticle Forces ◽  
Wetting Properties ◽  
Small Glass ◽  
Capillary Bridges ◽  
Scale Properties ◽  
Comparison Of The Results ◽  
Maximal Stability

ABSTRACTExperiments were performed under accurately-controlled humidity conditions in order to quantify effects induced by humidity on granular materials. Measurements of the maximal stability angle of a pile made of small glass beads are reported as a function of the relative vapor pressure in the cell, up to close to saturation. The comparison of the results obtained with fluids differing in their molecular interactions with glass, namely water and heptane, shows that the wetting properties of the interstitial liquid on the grains have a strong influence on the cohesion of the non-saturated granular medium. This suggests that gravimetric experiments which could indirectly give information on the size of the capillary bridges that form between grains should be useful to understand the close connection that exists, through interparticle forces, between microscopic properties such as wetting properties and surface roughness of the grains, and global-scale properties of the pile, as its stability and flowability.

Humidity Effects and Aging Behavior in Granular Media

1998 ◽  
Vol 543 ◽  
Author(s):  
F. Restagno ◽  
H. Gayvallet ◽  
L. Bocquet ◽  
E. Charlaix
Keyword(s):  
Relative Humidity ◽  
Granular Medium ◽  
Granular Media ◽  
Capillary Condensation ◽  
Glass Beads ◽  
Aging Behavior ◽  
Humidity Effects ◽  
Small Glass ◽  
Aging Properties ◽  
Maximum Stability

AbstractWe present a study of humidity effects on the maximum stability angle in granular media. We show that a granular medium of small glass beads exhibits aging properties: the first avalanche angle increases logarithmically with the resting time of the pile. This aging behavior is found to depend on the relative humidity of the surrounding atmosphere. A short interpretation of this effect, based on a model of activated capillary condensation, is proposed.

Penetration of spheres into loose granular media

2004 ◽  
Vol 82 (6) ◽  
pp. 439-446 ◽  
Author(s):  
J R de Bruyn ◽  
A M Walsh
Keyword(s):  
Yield Stress ◽  
Penetration Depth ◽  
Newtonian Fluid ◽  
Granular Medium ◽  
Effective Viscosity ◽  
Granular Media ◽  
Experimental Results ◽  
Incident Momentum ◽  
Small Glass ◽  
Zero Momentum

We study the penetration of steel spheres dropped vertically into a container of loosely packed, small glass beads. We find that the penetration depth of the spheres increases linearly with the incident momentum of the projectile, but with a zero-momentum intercept that can be either positive or negative. This behavior can be understood by modelling the granular medium as a non-Newtonian fluid with a yield stress and an effective viscosity. We derive the scaling behavior of the viscosity and find agreement with our experimental results. PACS Nos.: 45.70.–n, 83.80.Fg, 47.50.+d

scholarly journals Under pressure: Hydrogel swelling in a granular medium

2021 ◽  
Vol 7 (7) ◽  
pp. eabd2711
Author(s):  
Jean-François Louf ◽  
Nancy B. Lu ◽  
Margaret G. O’Connell ◽  
H. Jeremy Cho ◽  
Sujit S. Datta
Keyword(s):  
Oil Recovery ◽  
Granular Medium ◽  
Granular Media ◽  
Three Dimensional ◽  
Osmotic Swelling ◽  
Widespread Adoption ◽  
Dry Soil ◽  
Hydrogel Swelling

Hydrogels hold promise in agriculture as reservoirs of water in dry soil, potentially alleviating the burden of irrigation. However, confinement in soil can markedly reduce the ability of hydrogels to absorb water and swell, limiting their widespread adoption. Unfortunately, the underlying reason remains unknown. By directly visualizing the swelling of hydrogels confined in three-dimensional granular media, we demonstrate that the extent of hydrogel swelling is determined by the competition between the force exerted by the hydrogel due to osmotic swelling and the confining force transmitted by the surrounding grains. Furthermore, the medium can itself be restructured by hydrogel swelling, as set by the balance between the osmotic swelling force, the confining force, and intergrain friction. Together, our results provide quantitative principles to predict how hydrogels behave in confinement, potentially improving their use in agriculture as well as informing other applications such as oil recovery, construction, mechanobiology, and filtration.

GRANULAR MEDIA ON A VIBRATING PLATE: A MOLECULAR DYNAMICS SIMULATION

1993 ◽  
Vol 07 (09n10) ◽  
pp. 1779-1788 ◽  
Author(s):  
JASON A.C. GALLAS ◽  
HANS J. HERRMANN ◽  
STEFAN SOKOLOWSKI
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Granular Materials ◽  
Granular Medium ◽  
Granular Media ◽  
Dynamics Simulation ◽  
Dissipation Of Energy ◽  
Conveyor Belts ◽  
Good Agreement ◽  
Vibrating Plate

When sand or other granular materials are shaken, poured or sheared many intriguing phenomena can be observed. We will model the granular medium by a packing of elastic spheres and simulate it via Molecular Dynamics. Dissipation of energy and shear friction at collisions are included. The onset of fluidization can be determined and is in good agreement with experiments. On a vibrating plate we observe the formation of convection cells due to walls or amplitude modulations. Density and velocity profiles on conveyor belts are measured and the influence of an obstacle discussed. We mention various types of rheology for flow down an inclined chute or through a pipe and outflowing containers.

scholarly journals Development of Approaches to Creation of Active Vibration Control System in Problems of the Dynamics for Granular Media

2018 ◽  
Vol 148 ◽  
pp. 11004 ◽  
Author(s):  
Andrei P. Khomenko ◽  
Sergey K. Kargapoltsev ◽  
Andrey V. Eliseev
Keyword(s):  
Granular Medium ◽  
Granular Media ◽  
Active Vibration Control ◽  
Evaluation Criteria ◽  
Dynamic Interactions ◽  
Theoretical Understanding ◽  
Vibration Machine ◽  
Vibration Field ◽  
Steel Balls ◽  
Analytical Approaches

The article deals with the development of mathematical models and evaluation criteria of the vibration field in the dynamic interactions of the elements of the vibrational technological machines for the processes of vibrational strengthening of long-length parts with help of a steel balls working medium. The study forms a theoretical understanding of the modes of motions of material particles in interaction with a vibrating surface of the working body of the vibration machine. The generalized approach to the assessment of the dynamic quality of the work of vibrating machines in multiple modes of tossing, when the period of free flight of particles is a multiple of the period of the surface oscillations of the working body, is developed in the article. For the correction of vibration field of the working body, the characteristics of dynamic interactions of granular elements of the medium are taken into account using original sensors. The sensors that can detect different particularities of interaction of the granular medium elements at different points of the working body are proposed to evaluate the deviation from a homogeneous and one-dimensional mode of vibration field. Specially developed sensors are able to register interactions between a single granule, a system of granules in filamentous structures, and multipoint interactions of the elements in a close-spaced cylindrical structure. The system of regularization of the structure of vibration fields based on the introduction of motion translation devices is proposed using the multi-point sensor locations on the working body. The article refers to analytical approaches of the theory of vibration displacements. For the experimental data assessment, the methods of statistical analysis are applied. It is shown that the peculiar features of the motion of granular medium registered by the sensors can be used to build active control systems of field vibration.

The Regular Pattern of Demagnetizing Factor Behaviour of Various ‘Cores’ of Granule-Ball Chains

2015 ◽  
Vol 1083 ◽  
pp. 75-79
Author(s):  
Alexander Sandulyak ◽  
Anna Sandulyak ◽  
Vera Ershova ◽  
Petr Shkatov
Keyword(s):  
Granular Medium ◽  
Granular Media ◽  
Relative Size ◽  
Regular Pattern ◽  
Magnetic Media ◽  
Full Agreement ◽  
The Core ◽  
Demagnetizing Factor ◽  
Ferro Magnetic ◽  
The One

We analyze previously not studied issue on the value, nature and manifestation f a demagnetizing factor of effective channels-magnets formed in magnetized granular media by the chains of contacting granules. We provide the factor values for conditionally defined quasi-solid cores of the channels varying in length and diameter, as well as a corresponding consolidating expression which turned out to be exponential with such an argument as the radical of the core relative size. We emphasize full agreement of this expression with the one for a granular medium, i.e. the medium consisting, basically, of the effective channels bundle according to the developed theory of channel-by-channel (selective) magnetization of granular ferro-magnetic media used, e.g. as operating elements in versatile magnetic separators.

The permeability of magma mush assembled from anisotropic tabular crystals

2021 ◽  
Author(s):  
Eloïse Bretagne ◽  
Fabian B. Wadsworth ◽  
Katherine J. Dobson ◽  
Jérémie Vasseur ◽  
Jason P. Coumans
Keyword(s):  
Numerical Simulation ◽  
Granular Medium ◽  
Granular Media ◽  
Pore Space ◽  
A Priori ◽  
Spherical Particles ◽  
Natural Systems ◽  
Melt Extraction ◽  
Melt Segregation ◽  
Melt Accumulation

<p>The extraction of melt from a mush in a magma reservoir is of wide interest. All models for melt extraction from a mush require knowledge of mush permeability, and yet this remains poorly constrained. This permeability is typically calculated using the Kozeny-Carman model or variants thereof, which require a priori knowledge of the microstructural geometry. Such models are not calibrated or tested for packs of crystals of a range of shapes found in natural mush piles, leading to the potential for oversimplification of complex natural systems.</p><p>Essentially, a magma mush with minimal crystal-crystal intergrowth is composed of packed crystals where the pore space is filled with interstitial melt. Therefore, this can be studied as a granular medium. We use numerical methods to create domains of closely packed, randomly oriented cuboids in which we keep the short and intermediate axes lengths equal (i.e. square cross section) and vary the long axis magnitude. Our synthetic ‘crystals’ therefore cover the range from oblate to prolate, passing through a cubic shape. We supplement these with 3D numerical packs of spherical particles in cubic lattice arrangements or random arrangements. For the sphere packs we use various polydispersivity of sphere sizes. The permeability of all of these pack types is calculated using a numerical simulation (both LBflow and Avizo-based algorithms) with imposed periodic boundary conditions. The preliminary results suggest that the permeability of a granular medium scales with the specific surface area exclusively, without requiring prior knowledge of the geometry and size distribution of the particles.</p><p>We suggest that the model toward which we are working will allow magma mush permeability to be modelled more accurately. If our approach is embedded in existing continuum models for mush compaction and melt extraction, then more accurate estimates of melt accumulation rates prior to very large eruptions could be found.</p><p>Keywords: melt segregation, compaction, granular media, fluid flow, numerical simulation</p>

scholarly journals Rolling resistance of shallow granular deformation

2017 ◽  
Vol 473 (2207) ◽  
pp. 20170375
Author(s):  
Keaton J. Burns ◽  
Neil J. Balmforth ◽  
Ian J. Hewitt
Keyword(s):  
Theoretical Model ◽  
Granular Medium ◽  
Granular Media ◽  
Rolling Resistance ◽  
Optical Tracking ◽  
Leading Order ◽  
Air Drag ◽  
Glass Spheres ◽  
Acceleration Data ◽  
Model Predictions

Experiments are conducted to measure the resistance experienced by light cylinders rolling over flat beds of granular media. Sand and glass spheres are used for the beds. The trajectories of the rolling cylinders are determined through optical tracking, and velocity and acceleration data are inferred through fits to these trajectories. The rolling resistance is dominated by a velocity-independent component, but a velocity-dependent drag exceeding the expected strength of air drag is also observed. The results are compared to a theoretical model based on a cohesionless Mohr–Coulomb rheology for a granular medium in the presence of gravity. The model idealizes the flow pattern underneath the rolling cylinder as a plastically deforming zone in front of a rigidly rotating plug attached to the cylinder, as proposed previously for cylinders rolling on perfectly cohesive plastic media. The leading-order, rate-independent rolling resistance observed experimentally is well reproduced by the model predictions.

Scattering of Solitary Waves and Excitation of Transient Breathers in Granular Media by Light Intruders and No Precompression

2011 ◽  
Vol 79 (1) ◽  
Author(s):  
Yuli Starosvetsky ◽  
K. R. Jayaprakash ◽  
Alexander F. Vakakis
Keyword(s):  
Granular Medium ◽  
Granular Media ◽  
Multiple Scale ◽  
Hertzian Contact ◽  
Reduced Models ◽  
Strongly Nonlinear ◽  
Granular Chains ◽  
Low Amplitude ◽  
Excitation Conditions ◽  
Nonlinear Regimes

We analyze the dynamics of strongly nonlinear granular chains of beads in Hertzian contact with light intruders. We show that the interactions of the light intruders with solitary pulses propagating through the granular medium can be approximately studied by reduced models of the intruders with only their neighboring beads under similar excitation conditions. Studying the reduced models, we identify weakly and strongly nonlinear regimes in the dynamics, depending on the degree of compression between beads and on the occurrence of separation between neighboring beads leading to collisions. We analyze weakly and strongly nonlinear oscillatory regimes of the intruder dynamics by multiple-scale analysis, and by applying special nonsmooth coordinate transformations. When separation between beads occurs, localized transient breathers are excited, corresponding to repeated collisions of an intruder with its neighbors. This leads to high-frequency scattering energy, and to radiation of energy in the granular medium in the form of low-amplitude slowly modulated oscillatory pulses. We find that repeated excitation of localized transient breathers by an array of periodically placed intruders can result in drastic reduction of the amplitude of a solitary wave propagating through the granular medium. This indicates that this type of granular media can be designed as effective shock attenuators.

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