Discrete Element Models of Particle Flows

Wait, R.

doi:10.3846/13926292.2001.9637155

Cited by 15 publications

(5 citation statements)

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“…To determine particle flows, Wait (2001) developed a DEM that included only dynamic friction. Concurrently with this project's research, Rycroft et al (2006b) used a DEM, created for other purposes, to simulate the flow of pebbles through a pebble-bed reactor.…”

Section: Previous Workmentioning

confidence: 99%

“…where The static friction model contributes to the F ij term, which is also part of the F ij term. The mass and moment of inertia are calculated assuming spherical symmetry with the equations: The dynamic (or kinetic) friction model is based on the model described by Wait (2001). Wait's and the PEBBLES model calculate the dynamic friction using a combination of the relative velocities and pressure between the pebbles, as shown in Equations (4.7) and (4.8):…”

Section: Overview Of Modelmentioning

confidence: 99%

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Pebble-bed pebble motion: Simulation and Applications

Cogliati¹

2011

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Thanks are due to many people who have provided information, comments and insight. I apologize in advance for anyone that I have left out. Thanks go to Javier Ortensi for the encouragement and discussion as he figured out how use the earthquake data and I figured out how to generate it and for the assistance with the graphite dust portion. At INL the following people assisted: Rob Bratton and Will Windes with the graphite literature review, Brian Boer with discussion and German translation, Hongbin Zhang with encouragement and Chinese translation, Hans Gougar for the encouragement and ideas, and Suzette J. Payne for providing me with the earthquake motion data. The following PBMR (South Africa) employees provided valuable help locating graphite literature and data: Frederik Reitsma, Pieter Goede, and Alastair Ramlakan. The Juelich (Germany) people-Peter Pohl, Johannes Fachinger, and Werner von Lensa-provided valuable assistance with understanding AVR. Thanks to Professor Mary Dunzik-Gougar for introducing me to many of these people, as well as encouragement and feedback on this PhD and participating as co-chair on the dissertation committee. Thanks to the other members of my committee, Dr. Michael Lineberry, Dr. Steve C. Chiu and Dr. Steve Shropshire, for providing valuable feedback on the dissertation. Thanks to Gannon Johnson for pointing out that length needed to be tallied separately from the length times force tally for the wear calculation (this allowed the vibration issue to be found). Thanks to Professor Jan Leen Kloosterman of the Delft University of Technology for providing me the PEBDAN program used for calculating Dancoff factors. Thanks also to Akira Tokuhiro, Donald Carlson, and Luo Xiaowei for various suggestions. Thanks to Elizabeth Cogliati for proofreading a previous version of this report.

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Section: Previous Workmentioning

confidence: 99%

Section: Overview Of Modelmentioning

confidence: 99%

Pebble-bed pebble motion: Simulation and Applications

Cogliati¹

2011

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“…On the other hand, the continuous implicit function representations of bodies, for example, elliptical particles in 2D (Ting, 1992;Vu-Quoc, Zhang and Walton, 2000), ellipsoids in 3D (Lin and Ng, 1995), or superquadrics ( Figure 11) in 2D and 3D (Pentland and Williams, 1989;Williams and Pentland, 1992;Wait, 2001) …”

Section: Contact Resolution Phasementioning

confidence: 99%

Discrete Element Methods

Bícanić

2004

Encyclopedia of Computational Mechanics

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Discrete element methods (DEMs) comprise different techniques suitable for a simulation of dynamic behaviour of systems of multiple rigid, simply deformable (pseudo‐rigid), or fully deformable separated bodies of simplified or arbitrary shapes, subject to continuous changes in the contact status and varying contact forces, which in turn influence the subsequent movement of bodies. Such problems are nonsmooth in space (separate bodies) and in time (jumps in velocities upon collisions) and the unilateral constraints (nonpenetrability) need to be considered. A system of bodies changes its position continuously under the action of external forces and interaction forces between bodies, which may eventually lead to a steady state configuration, once static equilibrium is achieved. For rigid bodies, the contact interaction law is the only constitutive law considered, while the continuum constitutive law (e.g. elasticity, plasticity, damage, fracturing) needs to included for deformable bodies. Computational modeling of multibody contacts (both the contact detection and contact resolution) represents the dominant feature in DEMs, as the number of bodies considered may be very large. If the number of potential contact surfaces is relatively small (e.g. nonlinear finite element analysis of contact problems), it is convenient to define groups of nodes, segments, or surfaces that belong to a possible contact set a priori. These geometric attributes can then be continuously checked against one another and the kinematic resolution can be treated in a very rigorous manner. Bodies that are possibly in contact may be internally discretized by finite elements and their material behaviour can essentially be of any complexity. The category of DEMs specifically refers to simulations involving a large number of bodies where the contact locations and conditions cannot be defined in advance and need to be continuously updated as the solution progresses. DEMs are most frequently applied to macroscopically discrete system of bodies (jointed rock, granular flow) but have also beeen successfully utilized in a microscopic setting, where very simple interaction laws between individual particles provide the material behaviour observed at a homogenized, macroscopic level. The DEM is most commonly defined as a computational modeling framework that allows finite displacements and rotations of discrete bodies, including complete detachment and recognises new contacts automatically, as the calculation progresses. There are many methods (e.g. DEM, RBSM (rigid block spring method), DDA (discontinuous deformation analysis), DEM/FEM (combined discrete/finite elements), NSCD (nonsmooth contact dynamics)), which belong to a broad family of DEMs. Although these methods appear under different names and each of them is developing in its own right, there are many unifying aspects and a more general framework is emerging, which allows for equivalence between these apparently different methodologies to be recognised. Possible classification may be based on the manner these methods address (i) detection of contacts, (ii) treatment of contacts (rigid, deformable), (iii) deformability (constitutive law) of bodies in contact (rigid, deformable, elastic, elasto‐plastic etc), (iv) large displacements and large rotations, (v) number (small or large) and/or distribution (loose or dense packing) of interacting bodies considered, (vi) consideration of the model boundaries, (vii) possible subsequent fracturing or fragmentation, and (viii) time stepping integration schemes (explicit, implicit). DEMs are also used for problems where the discrete nature of the emerging discontinuities needs to be taken into account. Application ranges from modeling problems of a discontinuous behaviour a priori (granular and particulate materials, silo flow, sediment transport, jointed rocks, stone or brick masonry) to problems where the modeling of transition from a continuum to a discontinuum is more important. Increased complexity of different discontinuous models is achieved by incorporating the deformability of solid material and/or by more complex contact interaction laws, as well as by the introduction of some failure or fracturing criteria controlling the solid material behaviour and the emergence of new discontinuities. The chapter covers basic ideas behind the discrete element framework and ways of regularizing of nonsmooth contact conditions. It further discusses typical methods of geometrically characterizing interacting bodies, as well as algorithms for contact detection. Further topics include the imposition of contact constraints and boundary conditions, various ways of modeling block deformability. Modeling of fragmentation and transition from continuum to discontinuum is followed by an account of commonly adopted time interatation schemes. Finally, associated frameworks and unifying aspects of different frameworks belonging to the category of DEMs is discussed.

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“…Nowadays, to propose innovative processes, industries require the use of sophisticated simulation techniques. Some of these are based in the discrete element method (DEM), which use virtual models to simulate the dynamic flow of particulate solids [1] in transport, handling, storage, and process systems [2]. At present, DEM is drawing the attention of many designers and manufacturers of equipment as well as process engineers.…”

Section: Introductionmentioning

confidence: 99%

Analysis and Optimization of Material Flow inside the System of Rotary Coolers and Intake Pipeline via Discrete Element Method Modelling

et al. 2018

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There is hardly any industry that does not use transport, storage, and processing of particulate solids in its production process. In the past, all device designs were based on empirical relationships or the designer’s experience. In the field of particulate solids, however, the discrete element method (DEM) has been increasingly used in recent years. This study shows how this simulation tool can be used in practice. More specifically, in dealing with operating problems with a rotary cooler which ensures the transport and cooling of the hot fly ash generated by combustion in fluidized bed boilers. For the given operating conditions, an analysis of the current cooling design was carried out, consisting of a non-standard intake pipeline, which divides and supplies the material to two rotary coolers. The study revealed shortcomings in both the pipeline design and the cooler design. The material was unevenly dispensed between the two coolers, which combined with the limited transport capacity of the coolers, led to overflowing and congestion of the whole system. Therefore, after visualization of the material flow and export of the necessary data using DEM design measures to mitigate these unwanted phenomena were carried out.

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Discrete Element Models of Particle Flows

Cited by 15 publications

References 0 publications

Pebble-bed pebble motion: Simulation and Applications

Pebble-bed pebble motion: Simulation and Applications

Discrete Element Methods

Analysis and Optimization of Material Flow inside the System of Rotary Coolers and Intake Pipeline via Discrete Element Method Modelling

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