Autocorrelation functions of granular media with free arrangement of spheres, spherical shells or ellipsoids

ABSTRACTWhen an initially homogeneous binary mixture of granular media such as fine and coarse sand is poured near the closed edge of a “quasi-two-dimensional” Hele-Shaw cell consisting of two vertical transparent plates held a narrow distance apart, the mixture spontaneously forms alternating segregated layers. Experimental measurements of this stratification effect are reported in order to determine which model, one which suggests that segregation only occurs when the granular material contained within a metastable heap between the critical and maximum angle of repose avalanches down the free surface, or one for which the segregation results from smaller particles becoming trapped in the top surface and being removed from the moving layer during continuous flow. The result reported here indicate that the Metastable Wedge model provides a natural explanation for the initial mixed zone which precedes the formation of the layers, while the Continuous Flow model explains the observed upward moving kink of segregated material for higher granular flux rates, and that both mechansims are necessary in order to understand the observed pairing of segregated layersfor intermediate flow rates and cell separations.

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

JOURNAL OF ADVANCES IN PHYSICS ◽

10.24297/jap.v8i1.1530 ◽

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

Â 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 robotâ€™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 â€˜influencing domainâ€™ 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 vehicleâ€™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.

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Marangoni Convection in Spherical Shells

10.2514/6.iac-05-a2.4.07 ◽

2005 ◽

Author(s):

Pravin Subramanian ◽

Abdelfattah Zebib

Keyword(s):

Marangoni Convection ◽

Spherical Shells

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Thermal Convection in Rotating Spherical Shells: an Experimental and Numerical Approach within GeoFlow

57th International Astronautical Congress ◽

10.2514/6.iac-06-a2.2.05 ◽

2006 ◽

Author(s):

Mrs. Birgit Futterer ◽

Dr. Marcus Gellert ◽

Mr. Thomas von Larcher ◽

Mr. Christoph Egbers

Keyword(s):

Thermal Convection ◽

Numerical Approach ◽

Spherical Shells

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β-Cyclodextrin Polymers on Microcrystalline Cellulose as a Granular Media for Organic Micropollutant Removal from Water

10.26434/chemrxiv.7471508 ◽

2018 ◽

Author(s):

Diego Alzate-Sanchez ◽

Yuhan Ling ◽

Chenjun Li ◽

Benjamin Frank ◽

Reiner Bleher ◽

...

Keyword(s):

Microcrystalline Cellulose ◽

Continuous Flow ◽

Granular Media ◽

Anaerobic Biodegradation ◽

Thin Coating ◽

Micropollutant Removal ◽

Cyclodextrin Polymers ◽

Flow Experiments ◽

Aerobic And Anaerobic ◽

Cellulose Composite

This manuscript describes cyclodextrin polymers formed as a thin coating on microcrystalline cellulose. The resulting polymer/cellulose composite shows promising performance for removing organic pollutants from water and can be packed into columns for continuous-flow experiments. The polymer/cellulose composite also shows excellent resistance to aerobic and anaerobic biodegradation.

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THE THEORIES AND THE APPLICATIONS OF SHALLOW SPHERICAL SHELLS

Transactions of the Architectural Institute of Japan ◽

10.3130/aijsaxx.97.0_11 ◽

1964 ◽

Vol 97 (0) ◽

pp. 11-19

Author(s):

YOSHIKATSU TSUBOI

Keyword(s):

Spherical Shells

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Analysis of process of emulsions transport in hydrophilic/oleophilic granular porous media driven by capillary force

Technical Sciences ◽

10.31648/ts.2719 ◽

2018 ◽

Vol 2 (21) ◽

pp. 85-101

Author(s):

Olga Shtyka ◽

Łukasz Przybysz ◽

Mariola Błaszczyk ◽

Jerzy P. Sęk

Keyword(s):

Porous Media ◽

Experimental Research ◽

Granular Media ◽

Single Phase ◽

Influential Factor ◽

Dispersed Phase ◽

Porous Structures ◽

Phase Concentration ◽

Granular Porous Media ◽

Kinetics Of

The research focuses on the issues concerning a process of multiphase liquids transport in granular porous media driven by the capillary pressure. The current publication is meant to introduce the results of experimental research conducted to evaluate the kinetics of the imbibition and emulsions behavior inside the porous structures. Moreover, the influence of the dispersed phase concentration and granular media structure on the mentioned process was considered. The medium imbibition with emulsifier-stabilized emulsions composed of oil as the dispersed phase in concentrations of 10 vol%, 30 vol%, and 50 vol%, was investigated. The porous media consisted of oleophilic/hydrophilic beads with a fraction of 200–300 and 600–800 μm. The experimental results provided that the emulsions imbibition in such media depended stronger on its structure compare to single-phase liquids. The increase of the dispersed phase concentration caused an insignificant mass decreasing of the imbibed emulsions and height of its penetration in a sorptive medium. The concentrations of the imbibed dispersions exceeded their initial values, but reduced with permeants front raise in the granular structures that can be defined as the influential factor for wicking process kinetics.

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