Fluctuations and self-diffusion of sheared granular material flows

1999 ◽  
Vol 43 (5) ◽  
pp. 1049-1066 ◽  
Author(s):  
Shu-San Hsiau ◽  
Yuh-Min Shieh
Keyword(s):  
Granular Material ◽  
Material Flows ◽  
Self Diffusion

Granular Material Flows

2007 ◽  
pp. 37-54
Author(s):  
Peter A. Markowich ◽  
Giuseppe Toscani
Keyword(s):  
Granular Material ◽  
Material Flows

scholarly journals Local measurements of velocity fluctuations and diffusion coefficients for a granular material flow

1995 ◽  
Vol 304 ◽  
pp. 1-25 ◽  
Author(s):  
V. V. R. Natarajan ◽  
M. L. Hunt ◽  
E. D. Taylor
Keyword(s):  
Granular Material ◽  
Diffusion Coefficients ◽  
Transverse Direction ◽  
Vertical Channel ◽  
Polished Glass ◽  
The Self ◽  
Velocity Fluctuations ◽  
Frictional Contacts ◽  
Self Diffusion ◽  
Two Dimensional Flow

Measurements were made of two components of the average and fluctuating velocities, and of the local self-diffusion coefficients in a flow of granular material. The experiments were performed in a 1 m-high vertical channel with roughened sidewalls and with polished glass plates at the front and the back to create a two-dimensional flow. The particles used were glass spheres with a nominal diameter of 3 mm. The flows were high density and were characterized by the presence of long-duration frictional contacts between particles. The velocity measurements indicated that the flows consisted of a central uniform regime and a shear regime close to the walls. The fluctuating velocities in the transverse direction increased in magnitude from the centre towards the walls. A similar variation was not observed for the streamwise fluctuations. The self-diffusion coefficients showed a significant dependence on the fluctuating velocities and the shear rate. The velocity fluctuations were highly anistropic with the streamwise components being 2 to 2.5 times the transverse components. The self-diffusion coefficients for the streamwise direction were an order-of-magnitude higher than those for the transverse direction. The surface roughness of the particles led to a decrease in the self-diffusion coefficients.

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.

Granular material flows – An overview

2006 ◽  
Vol 162 (3) ◽  
pp. 208-229 ◽  
Author(s):  
Charles S. Campbell
Keyword(s):  
Granular Material ◽  
Material Flows

Optical technique DPIV in measurements of granular material flows, Part 1 of 3—plane hoppers

2005 ◽  
Vol 60 (2) ◽  
pp. 589-598 ◽  
Author(s):  
I. Sielamowicz ◽  
S. Blonski ◽  
T.A. Kowalewski
Keyword(s):  
Granular Material ◽  
Optical Technique ◽  
Material Flows

Kinetic Theory Analysis of Flow-Induced Particle Diffusion and Thermal Conduction in Granular Material Flows

1993 ◽  
Vol 115 (3) ◽  
pp. 541-548 ◽  
Author(s):  
S. S. Hsiau ◽  
M. L. Hunt
Keyword(s):  
Thermal Conductivity ◽  
Kinetic Theory ◽  
Granular Material ◽  
Effective Thermal Conductivity ◽  
Mixing Layer ◽  
Theory Model ◽  
Simple Shear Flow ◽  
Experimental Measurements ◽  
Material Flows ◽  
Analytical Relations

The present study on granular material flows develops analytical relations for the flow-induced particle diffusivity and thermal conductivity based on the kinetic theory of dense gases. The kinetic theory model assumes that the particles are smooth, identical, and nearly elastic spheres, and that the binary collisions between the particles are isotropically distributed throughout the flow. The particle diffusivity and effective thermal conductivity are found to increase with the square root of the granular temperature, a term that quantifies the kinetic energy of the flow. The theoretical particle diffusivity is used to predict diffusion in a granular-flow mixing layer, and to compare qualitatively with recent experimental measurements. The analytical expression for the effective thermal conductivity is used to define an apparent Prandtl number for a simple-shear flow; this result is also qualitatively compared with experimental measurements. The differences between the predictions and the measurements suggest limitations in applying kinetic theory concepts to actual granular material flows, and the need for more detailed experimental measurements.

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