scholarly journals Liquid clustering and capillary pressure in granular media

2014 ◽  
Vol 762 ◽  
Author(s):  
Jean-Yves Delenne ◽  
Vincent Richefeu ◽  
Farhang Radjai
Keyword(s):  
Granular Material ◽  
Granular Media ◽  
Capillary Condensation ◽  
Peak Stress ◽  
Secondary Process ◽  
Coalescence Process ◽  
Liquid Distribution ◽  
Lattice Boltzmann Simulations ◽  
Liquid Clusters ◽  
Condensed Liquid

AbstractBy means of extensive lattice Boltzmann simulations, we investigate the process of growth and coalescence of liquid clusters in a granular material as the amount of liquid increases. A homogeneous grain–liquid mixture is obtained by means of capillary condensation, thus providing meaningful statistics on the liquid distribution inside the granular material. The tensile stress carried by the grains as a function of the amount of condensed liquid reveals four distinct states, with a peak stress occurring at the transition from a primary coalescence process, where the cohesive strength is carried mostly by the grains, to a secondary process governed by the increase of the liquid cluster volumes. We show that the evolution of capillary states is correctly captured by a simple model accounting for the competing effects of the Laplace pressure and grain–liquid interface.

Stress fields in granular material and implications for performance of robot locomotion over granular media

2015 ◽  
Vol 8 (1) ◽  
pp. 2005-2009
Author(s):  
Diandong Ren ◽  
Lance M. Leslie ◽  
Congbin Fu
Keyword(s):  
Mechanical Properties ◽  
Granular Material ◽  
Granular Media ◽  
Rotation Frequency ◽  
Legged Locomotion ◽  
Working Environment ◽  
Navier Stokes ◽  
Maximum Speed ◽  
Sigmoid Curve ◽  
Multi Body

 Legged locomotion of robots has advantages in reducing payload in contexts such as travel over deserts or in planet surfaces. A recent study (Li et al. 2013) partially addresses this issue by examining legged locomotion over granular media (GM). However, they miss one extremely significant fact. When the robot’s wheels (legs) run over GM, the granules are set into motion. Hence, unlike the study of Li et al. (2013), the viscosity of the GM must be included to simulate the kinematic energy loss in striking and passing through the GM. Here the locomotion in their experiments is re-examined using an advanced Navier-Stokes framework with a parameterized granular viscosity. It is found that the performance efficiency of a robot, measured by the maximum speed attainable, follows a six-parameter sigmoid curve when plotted against rotating frequency. A correct scaling for the turning point of the sigmoid curve involves the footprint size, rotation frequency and weight of the robot. Our proposed granular response to a load, or the ‘influencing domain’ concept points out that there is no hydrostatic balance within granular material. The balance is a synergic action of multi-body solids. A solid (of whatever density) may stay in equilibrium at an arbitrary depth inside the GM. It is shown that there exists only a minimum set-in depth and there is no maximum or optimal depth. The set-in depth of a moving robot is a combination of its weight, footprint, thrusting/stroking frequency, surface property of the legs against GM with which it has direct contact, and internal mechanical properties of the GM. If the vehicle’s working environment is known, the wheel-granular interaction and the granular mechanical properties can be grouped together. The unitless combination of the other three can form invariants to scale the performance of various designs of wheels/legs. Wider wheel/leg widths increase the maximum achievable speed if all other parameters are unchanged.

Capillary condensation in wet granular media via meso-scale Monte Carlo simulation

2009 ◽  
Author(s):  
Benjamin D. Zeidman ◽  
David T. Wu ◽  
Ning Lu ◽  
Mark T. Lusk ◽  
Masami Nakagawa ◽  
...  
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Granular Media ◽  
Capillary Condensation ◽  
Meso Scale

A New Simple Non Linear Modelling of the Quasi Statics of Granular Media: predictions, comparisons with experiments

2000 ◽  
Vol 627 ◽  
Author(s):  
Pierre Evesque
Keyword(s):  
Granular Material ◽  
Granular Media ◽  
Stress Ratio ◽  
Rheological Behaviour ◽  
Stress Strain ◽  
Linear Modelling ◽  
Non Linear ◽  
Strain Paths ◽  
Contact Distribution

ABSTRACTFirst, a non linear incremental modelling is proposed to describe rheological behaviour of granular material under different simple (i.e. triaxial-, oedometric-, undrained-) stress-strain paths. Validity of isotropic-response assumption is demonstrated whatever the stress ratio as far as deformation range remains small (ε1<5%). This contradicts some recent hypothesis made on the evolution of contact distribution during anisotropic loading.

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.

scholarly journals Lattice Boltzmann modelling of liquid distribution in unsaturated granular media

2016 ◽  
Vol 80 ◽  
pp. 353-359 ◽  
Author(s):  
Vincent Richefeu ◽  
Farhang Radjai ◽  
Jean-Yves Delenne
Keyword(s):  
Lattice Boltzmann ◽  
Granular Media ◽  
Liquid Distribution

COMPACTION AND DENSITY FLUCTUATIONS IN VIBRATED GRANULAR MEDIA

2001 ◽  
Vol 04 (04) ◽  
pp. 389-396
Author(s):  
A. C. B. BARNUM ◽  
ARIF OZBAY ◽  
E. R. NOWAK
Keyword(s):  
Steady State ◽  
Granular Material ◽  
Time Scale ◽  
Granular Media ◽  
Cylindrical Tube ◽  
Density Fluctuations ◽  
Noise Power ◽  
Third Order ◽  
State Densities ◽  
Irreversible Relaxation

We report measurements of the density of a vibrated granular material as a function of time or taps. The material studied consists of monodisperse spherical glass beads confined to a long, thin cylindrical tube. Changes in vibration intensity are used to induce transitions between two steady state densities that depend on the intensity of the vibrations. We find a complex time evolution similar to previous work on the irreversible relaxation from a loose state toward a steady state. In addition, frequency dependent third order moments of the density fluctuations are measured. The data indicate a coupling between large variations in density on one time scale and noise power over a broad range of higher-frequency scales.

Mechanics of Nanocrystalline Particles With the Distinct Element Method

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Igor Ostanin ◽  
Yuezhou Wang ◽  
Yuxiang Ni ◽  
Traian Dumitricǎ
Keyword(s):  
Granular Media ◽  
Experimental Testing ◽  
Distinct Element ◽  
Peak Stress ◽  
Distinct Element Method ◽  
Nanocrystalline Particles ◽  
Testing Data ◽  
Nanocrystalline Structures ◽  
Contact Models ◽  
Element Method

In geomechanics and civil engineering, the distinct element method (DEM) is employed in a top-down manner to simulate problems involving mechanics of granular media. Because this particle-based method is well adapted to discontinuities, we propose here to adapt DEM at the mesoscale in order to simulate the mechanics of nanocrystalline structures. The modeling concept is based on the representation of crystalline nanograins as mesoscopic distinct elements. The elasticity, plasticity, and fracture processes occurring at the interfaces are captured with contact models of interaction between elements. Simulations that rely on the fitting of the peak stress, strain, and failure mode on the experimental testing of Au and CdS hollow nanocrystalline particles illustrate the promising potential of mesoscopic DEM for bridging the atomistic-scale simulations with experimental testing data.

scholarly journals Granular Media Friction Pad for Robot Shoes—Hexagon Patterning Enhances Friction on Wet Surfaces

2021 ◽  
Vol 11 (23) ◽  
pp. 11287
Author(s):  
Halvor T. Tramsen ◽  
Lars Heepe ◽  
Stanislav N. Gorb
Keyword(s):  
Internal Friction ◽  
Granular Material ◽  
Contact Area ◽  
Granular Media ◽  
Elastic Membrane ◽  
Mechanical Interlocking ◽  
Material Flows ◽  
Friction Forces ◽  
Jamming Transition ◽  
Universal Applicability

For maximizing friction forces of the robotic legs on an unknown/unpredictable substrate, we introduced the granular media friction pad, consisting of a thin elastic membrane encasing loosely filled granular material. On coming into contact with a substrate, the fluid-like granular material flows around the substrate asperities and achieves large contact areas with the substrate. Upon applying load, the granular material undergoes the jamming transition, rigidifies and becomes solid-like. High friction forces are generated by mechanical interlocking on rough substrates, internal friction of the granular media and by the enhanced contact area caused by the deformation of the membrane. This system can adapt to a large variety of dry substrate topologies. To further increase its performance on moist or wet substrates, we adapted the granular media friction pad by structuring the outside of the membrane with a 3D hexagonal pattern. This results in a significant increase in friction under lubricated conditions, thus greatly increasing the universal applicability of the granular media friction pad for a multitude of environments.

GRAIN NON-SPHERICITY EFFECTS ON THE ANGLE OF REPOSE OF GRANULAR MATERIAL

1993 ◽  
Vol 07 (09n10) ◽  
pp. 2037-2046 ◽  
Author(s):  
JASON A.C. GALLAS ◽  
STEFAN SOKOLOWSKI
Keyword(s):  
Granular Material ◽  
Granular Media ◽  
Angle Of Repose ◽  
Site Model ◽  
Specific Effects ◽  
A Site ◽  
Spherical Grains

We use a site-site model to describe non-sphericity of particles composing a granular media. Specific effects of grain non-sphericity 011 the angle of repose are investigated. We report evidence indicating the possible existence of a shape-roughness threshold for grains: below it angles of repose are essentially the same as those obtained for spherical grains; above it there are pronounced changes 011 the angle of repose and it is possible to find rather large piles of grains.

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