Imperial College London

Dr Raphael (Rafi) Blumenfeld

Faculty of EngineeringDepartment of Earth Science & Engineering

Research Fellow
 
 
 
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Contact

 

r.blumenfeld Website

 
 
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Location

 

2.51Royal School of MinesSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
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112 results found

Amitai S, Bertei A, Blumenfeld R, Theory-based design of sintered granular composites triples three-phase boundary in fuel cells

Solid-oxide fuel cells produce electric current from energy released by aspontaneous redox reaction. The efficiency of these devices depends cruciallyon the microstructure of their electrodes and, in particular, on thethree-phase boundary (TPB) length, along which the energy-producing reactionoccurs. We present a systematic maximisation of the TPB length as a function offour readily-controllable microstructural parameters, for any given meanhydraulic radius that enables free gas flow. We identify the maximisingparameters and show that the TPB length can be increased by a factor of over300% compared to current common practices. We support this result bycalculating the TPB of several numerically simulated structures. We alsocompare four models for a single intergranular contact in the sinteredelectrode and show that the model commonly used in the SOFC literature isoversimplified and unphysical. We then propose two alternatives.

JOURNAL ARTICLE

Amitai S, Blumenfeld R, 2017, Modifying continuous-time random walks to model finite-size particle diffusion in granular porous media, GRANULAR MATTER, Vol: 19, ISSN: 1434-5021

JOURNAL ARTICLE

Blumenfeld R, Amitai S, Jordan JF, Hihinashvili Ret al., 2017, Comment on "Failure of the Volume Function in Granular Statistical Mechanics and an Alternative Formulation" Reply, PHYSICAL REVIEW LETTERS, Vol: 119, ISSN: 0031-9007

JOURNAL ARTICLE

Blumenfeld R, Ma J, 2017, Bending back stress chains and unique behaviour of granular matter in cylindrical geometries, GRANULAR MATTER, Vol: 19, ISSN: 1434-5021

JOURNAL ARTICLE

Matsushima T, Blumenfeld R, 2017, Fundamental structural characteristics of planar granular assemblies: Self-organization and scaling away friction and initial state, PHYSICAL REVIEW E, Vol: 95, ISSN: 2470-0045

JOURNAL ARTICLE

Blumenfeld R, Amitai S, Jordan JF, Hihinashvili Ret al., 2016, Failure of the Volume Function in Granular Statistical Mechanics and an Alternative Formulation, PHYSICAL REVIEW LETTERS, Vol: 116, ISSN: 0031-9007

JOURNAL ARTICLE

Huang L, Ran X, Blumenfeld R, 2016, Vertical dynamics of a horizontally oscillating active object in a two-dimensional granular medium., Phys Rev E, Vol: 94

We use a discrete-element method simulation and analytical considerations to study the dynamics of a self-energized object, modeled as a disk, oscillating horizontally within a two-dimensional bed of denser and smaller particles. We find that, for given material parameters, the immersed object (IO) may rise, sink, or not change depth, depending on the oscillation amplitude and frequency, as well as on the initial depth. With time, the IO settles at a specific depth that depends on the oscillation parameters. We construct a phase diagram of this behavior in the oscillation frequency and velocity amplitude variable space. We explain the observed rich behavior by two competing effects: climbing on particles, which fill voids opening under the disk, and sinking due to bed fluidization. We present a cavity model that allows us to derive analytically general results, which agree very well with the observations and explain quantitatively the phase diagram. Our specific analytical results are the following. (i) Derivation of a critical frequency, f_{c}, above which the IO cannot float up against gravity. We show that this frequency depends only on the gravitational acceleration and the IO size. (ii) Derivation of a minimal amplitude, A_{min}, below which the IO cannot rise even if the frequency is below f_{c}. We show that this amplitude also depends only on the gravitational acceleration and the IO size. (iii) Derivation of a critical value, g_{c}, of the IO's acceleration amplitude, below which the IO cannot sink. We show that the value of g_{c} depends on the characteristics of both the IO and the granular bed, as well as on the initial IO's depth.

JOURNAL ARTICLE

Blumenfeld R, Edwards SF, 2014, Granular statistical mechanics - a personal perspective, EUROPEAN PHYSICAL JOURNAL-SPECIAL TOPICS, Vol: 223, Pages: 2189-2204, ISSN: 1951-6355

JOURNAL ARTICLE

Matsushima T, Blumenfeld R, 2014, Universal Structural Characteristics of Planar Granular Packs, PHYSICAL REVIEW LETTERS, Vol: 112, ISSN: 0031-9007

JOURNAL ARTICLE

Blumenfeld R, Jordan JF, Edwards SF, 2013, Granular Statistical Mechanics: Volume-Stress Phase Space, Equipartition and Equations of State, 7th International Conference on Micromechanics of Granular Media (Powders and Grains), Publisher: AMER INST PHYSICS, Pages: 1186-1189, ISSN: 0094-243X

CONFERENCE PAPER

Matsushima T, Blumenfeld R, 2013, Microstructural characteristics of planar granular solids, POWDERS AND GRAINS 2013, Vol: 1542, Pages: 325-328, ISSN: 0094-243X

JOURNAL ARTICLE

Blumenfeld R, Edwards SF, 2012, Theory of Strains in Auxetic Materials, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, Vol: 25, Pages: 565-571, ISSN: 1557-1939

JOURNAL ARTICLE

Blumenfeld R, Jordan JF, Edwards SF, 2012, Interdependence of the Volume and Stress Ensembles and Equipartition in Statistical Mechanics of Granular Systems, PHYSICAL REVIEW LETTERS, Vol: 109, ISSN: 0031-9007

JOURNAL ARTICLE

Hihinashvili R, Blumenfeld R, 2012, Statistical-mechanical characteristics of dense planar granular systems, GRANULAR MATTER, Vol: 14, Pages: 277-282, ISSN: 1434-5021

JOURNAL ARTICLE

Hihinashvili R, Blumenfeld R, 2011, Structural Characterization of Porous and Granular Materials, 16th European Symposium on Improved Oil Recovery 2011

The morphological details of permeable porous materials impact significantly their macro-scale properties and in particular transport properties (e.g. permeability). A programme to derive macroscopic behaviour and responses from pore-scale information is a holy grail in the field. We report here progress on, and tests of, a recently proposed such a programme.The main steps of the programme are as follows. The solid phase of a porous material is first skeletonised into a framework of nodes and edges. Then the local structure is quantified by means of structure tensors, which describe the shape of novel volume elements called quadrons. Next, the local tensor description is used in an entropy-based statistical formalism to compute macroscopic structural characteristics as expectation values over a certain partition function. From the structural characteristics, physical properties can be evaluated. The 'thickened' structure is taken account of with an additional partition function, giving more accurate evaluation of structural and physical properties.Here we present tests for the initial stages of the programme. The tests are carried out on numerically generated two-dimensional granular aggregates. Specifically, we describe results on the statistics of the quadrons and the structural tensors.

CONFERENCE PAPER

Schwartz M, Blumenfeld R, 2011, Plug flow formation and growth in Da Vinci fluids, GRANULAR MATTER, Vol: 13, Pages: 241-245, ISSN: 1434-5021

JOURNAL ARTICLE

Blumenfeld R, 2010, Stress transmission and incipient yield flow in dense granular materials, IUTAM-ISIMM Symposium on Mathematical Modeling and Physical Instances of Granular Flows, Publisher: AMER INST PHYSICS, Pages: 167-182, ISSN: 0094-243X

CONFERENCE PAPER

Blumenfeld R, 2010, Stress transmission and incipient yield flow in dense granular materials, IUTAM-ISIMM Symposium on Mathematical Modeling and Physical Instances of Granular Flows, Editors: Goddard, Giovine, Jenkins, Publisher: Amer Inst of Physics, Pages: 167-182, ISBN: 9780735407725

This symposium brought together mathematicians, physicists and engineers interested in the continuing development and application of mathematical models of granular matter.

BOOK CHAPTER

Blumenfeld R, Edwards SF, Schwartz M, 2010, da Vinci fluids, catch-up dynamics and dense granular flow, EUROPEAN PHYSICAL JOURNAL E, Vol: 32, Pages: 333-338, ISSN: 1292-8941

JOURNAL ARTICLE

Hihinashvili R, Blumenfeld R, 2010, STRUCTURAL CHARACTERIZATION OF POROUS AND GRANULAR MATERIALS, 18th International Conference on Computational Methods in Water Resources (CMWR), Publisher: INT CENTER NUMERICAL METHODS ENGINEERING, Pages: 842-849

CONFERENCE PAPER

Blumenfeld R, Edwards SF, 2009, On Granular Stress Statistics: Compactivity, Angoricity, and Some Open Issues, JOURNAL OF PHYSICAL CHEMISTRY B, Vol: 113, Pages: 3981-3987, ISSN: 1520-6106

JOURNAL ARTICLE

Frenkel G, Blumenfeld R, King PR, Blunt MJet al., 2009, Topological Analysis of Foams and Tetrahedral Structures, ADVANCED ENGINEERING MATERIALS, Vol: 11, Pages: 169-176, ISSN: 1438-1656

JOURNAL ARTICLE

Frenkel G, Blumenfeld R, Grof Z, King PRet al., 2008, Structural characterization and statistical properties of two-dimensional granular systems, PHYSICAL REVIEW E, Vol: 77, ISSN: 1539-3755

JOURNAL ARTICLE

Frenkel G, Blumenfeld R, King PR, Blunt Met al., 2008, Topological analysis of foams and tetrahedral structures, Porous Metals and Metallic Foams: Metfoam 2007, Editors: Lefebvre, Banhart, Dunand, Publisher: DEStech Publications, Inc, ISBN: 9781932078282

BOOK CHAPTER

Frenkel G, King PR, Blunt MJ, Blumenfeld Ret al., 2008, Topological Analysis of Foams and Tetrahedral Structures, 5th Biennial International Conference on Porous Metals and Metallic Foams (MetFoam 2007), Publisher: DESTECH PUBLICATIONS, INC, Pages: 437-440

CONFERENCE PAPER

Gerritsen M, Kreiss G, Blumenfeld R, 2008, Analysis of stresses in two-dimensional isostatic granular systems, PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS, Vol: 387, Pages: 6263-6276, ISSN: 0378-4371

JOURNAL ARTICLE

Gerritsen M, Kreiss G, Blumenfeld R, 2008, Stress chain solutions in two-dimensional isostatic granular systems: Fabric-dependent paths, leakage, and branching, PHYSICAL REVIEW LETTERS, Vol: 101, ISSN: 0031-9007

JOURNAL ARTICLE

Blumenfeld R, 2007, On entropic characterization of granular materials, 20th Canberra International Physics Summer School and Workshop on Granular Materials, Publisher: WORLD SCIENTIFIC PUBL CO PTE LTD, Pages: 43-53

CONFERENCE PAPER

Blumenfeld R, 2007, Stresses in two-dimensional isostatic granular systems: exact solutions, NEW JOURNAL OF PHYSICS, Vol: 9, ISSN: 1367-2630

JOURNAL ARTICLE

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