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Article
Publication date: 1 February 1992

PETER A. CUNDALL and ROGER D. HART

Discrete element methods are numerical procedures for simulating the complete behaviour of systems of discrete, interacting bodies. Three important aspects of discrete…

Abstract

Discrete element methods are numerical procedures for simulating the complete behaviour of systems of discrete, interacting bodies. Three important aspects of discrete element programs are examined: (1) the representation of contacts; (2) the representation of solid material; and (3) the scheme used to detect and revise the set of contacts. A proposal is made to define what constitutes a discrete element program, and four classes of such programs are described: the distinct element method, modal methods, discontinuous deformation analysis and the momentum‐exchange method. Several applications and examples are presented, and a list is given of suggestions for future developments.

Details

Engineering Computations, vol. 9 no. 2
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 9 October 2009

J. Kozicki and F.V. Donzé

YADE‐OPEN DEM is an open‐source software based on the discrete element method, (DEM) which uses object oriented programming techniques. The purpose of this paper is to…

Abstract

Purpose

YADE‐OPEN DEM is an open‐source software based on the discrete element method, (DEM) which uses object oriented programming techniques. The purpose of this paper is to describe the software architecture.

Design/methodology/approach

The DEM chosen uses position, orientation, velocity and angular velocity as independent variables of simulated particles which are subject to explicit leapfrog time‐integration scheme (Lagrangian method). The three‐dimensional dynamics equations based on the classical Newtonian approach for the second law of motion are used. The track of forces and moments acting on each particle is kept at every time step. Contact forces depend on the particle geometry overlap and material properties. The normal, tangential and moment components of interaction force are included.

Findings

An effort is undertaken to extract the underlying object oriented abstractions in the DEM. These abstractions are implemented in C++, conform to object oriented design principles and use design patterns. Based on that, a software framework is developed in which the abstractions provide the interface where the modelling methods can be plugged‐in.

Originality/value

The resulting YADE‐OPEN DEM framework is designed in a generic way which provides great flexibility when adding new scientific simulation code. Some of the advantages are that numerous simulation methods can be coupled within the same framework while plug‐ins can import data from other software. In addition, this promotes code improvement through open‐source development and allows feedback from the community. However implementing such models requires that one adheres to the framework design and the YADE framework is a new emerging software. To download the software see http : //yade.wikia.com webpage.

Details

Engineering Computations, vol. 26 no. 7
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 16 April 2018

Boning Zhang, Richard Regueiro, Andrew Druckrey and Khalid Alshibli

This paper aims to construct smooth poly-ellipsoid shapes from synchrotron microcomputed tomography (SMT) images on sand and to develop a new discrete element method (DEM…

Abstract

Purpose

This paper aims to construct smooth poly-ellipsoid shapes from synchrotron microcomputed tomography (SMT) images on sand and to develop a new discrete element method (DEM) contact detection algorithm.

Design/methodology/approach

Voxelated images generated by SMT on Colorado Mason sand are processed to construct smooth poly-ellipsoidal particle approximations. For DEM contact detection, cuboidal shape approximations to the poly-ellipsoids are used to speed up contact detection.

Findings

The poly-ellipsoid particle shape approximation to Colorado Mason sand grains is better than a simpler ellipsoidal approximation. The new DEM contact algorithm leads to significant speedup and accuracy is maintained.

Research limitations/implications

The paper limits particle shape approximation to smooth poly-ellipsoids.

Practical implications

Poly-ellipsoids provide asymmetry of particle shapes as compared to ellipsoids, thus allowing closer representation of real sand grain shapes that may be angular and unsymmetric. When incorporated in a DEM for computation, the poly-ellipsoids allow better representation of particle rolling, sliding and interlocking phenomena.

Originality/value

Method to construct poly-ellipsoid particle shapes from SMT data on real sands and computationally efficient DEM contact detection algorithm for poly-ellipsoids.

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Article
Publication date: 1 March 2004

J.P. Morris, M.B. Rubin, S.C. Blair, L.A. Glenn and F.E. Heuze

We present the preliminary results from a parameter study investigating the stability of underground structures in response to explosion‐induced strong ground motions. In…

Abstract

We present the preliminary results from a parameter study investigating the stability of underground structures in response to explosion‐induced strong ground motions. In practice, even the most sophisticated site characterization may lack key details regarding precise joint properties and orientations within the rock mass. Thus, in order to place bounds upon the predicted behavior of a given facility, an extensive series of simulations representing different realizations may be required. The influence of both construction parameters (reinforcement, rock bolts, liners) and geological parameters (joint stiffness, joint spacing and orientation, and tunnel diameter to block size ratio) must be considered. We discuss the distinct element method (DEM) with particular emphasis on techniques for achieving improved computational efficiency, including the handling of contact detection and approaches to parallelization. We introduce a new approach for simulating deformation of the discrete blocks using the theory of a Cosserat point, which does not require internal discretization of the blocks. We also outline the continuum techniques we employ to obtain boundary conditions for the distinct element simulations. We present results from simulations of dynamic loading of several generic subterranean facilities in hard rock, demonstrating the suitability of the DEM for this application. These results demonstrate the significant role that joint geometry plays in determining the response of a given facility.

Details

Engineering Computations, vol. 21 no. 2/3/4
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 February 1992

KEVIN M. O'CONNOR and CHARLES H. DOWDING

To simulate the kinematics associated with mining‐induced subsidence in a blocky rock mass, a hybrid rigid block model was developed by combining a small displacement code…

Abstract

To simulate the kinematics associated with mining‐induced subsidence in a blocky rock mass, a hybrid rigid block model was developed by combining a small displacement code with a large displacement code. Gravity was applied to a rigid block mesh using an implicit formulation and the equilibrium displacements are then used as initial conditions for an explicit analysis in which excavation of a longwall mine panel and subsequent subsidence was simulated. A parameter study was performed to evaluate the influence of rigid block contact stiffness, vertical joint density, and contact roughness on mining‐induced strata movements for comparison with previously obtained field measurements. The best agreement between measured and calculated displacements was obtained when a relatively low stiffness value was maintained constant for all contacts. A surprising result was that neither increasing the density of vertical joints nor reducing the rigid block contact roughness improved the agreement between measured and simulated displacements.

Details

Engineering Computations, vol. 9 no. 2
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 March 1977

Clive Bingley, Helen Moss and Clive Martin

DIFFICULT to judge whether obstinacy, optimism or mere force of habit was the prime motivation for the reintroduction in Parliament in late January of another PLR Bill…

Abstract

DIFFICULT to judge whether obstinacy, optimism or mere force of habit was the prime motivation for the reintroduction in Parliament in late January of another PLR Bill— effected by prominent campaigner Lord (Ted) Willis.

Details

New Library World, vol. 78 no. 3
Type: Research Article
ISSN: 0307-4803

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Article
Publication date: 28 April 2014

Mark A. Hopkins

– The purpose of this paper is to present a new and efficient technique for discrete element modelling using non-convex polyhedral grain shapes.

Abstract

Purpose

The purpose of this paper is to present a new and efficient technique for discrete element modelling using non-convex polyhedral grain shapes.

Design/methodology/approach

The efficiency of the technique follows from the use of grains that are dilated versions of the basic polyhedral grain shapes. Dilation of an arbitrary polyhedral grain is accomplished by placing the center of a sphere of fixed radius at every point on the surface. The dilated vertices become sphere segments and the edges become cylinder segments. The sharpness of the vertices and edges can be adjusted by varying the dilation radius. Contacts between two dilated polyhedral grains can be grouped into three categories; vertex on surface, vertex on edge, and edge on edge, or in the grammar of the model, sphere on polygonal surface, sphere on cylinder, and cylinder on cylinder. Simple, closed-form solutions exist for each of these cases.

Findings

The speed of the proposed polyhedral discrete element model is compared to similar models using spherical and ellipsoidal grains. The polyhedral code is found to run about 40 percent as fast as an equivalent code using spherical grains and about 80 percent as fast as an equivalent code using ellipsoidal grains. Finally, several applications of the polyhedral model are illustrated.

Originality/value

Few examples of discrete element modeling studies in the literature use polyhedral grains. This dearth is because of the perceived complexity of the polyhedral coding challenges and the slow speed of the codes compared to codes for other grain shapes. This paper presents a much simpler approach to discrete element modeling using polyhedral grain shapes.

Details

Engineering Computations, vol. 31 no. 3
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 21 August 2009

John F. Peters, Mark A. Hopkins, Raju Kala and Ronald E. Wahl

The purpose of this paper is to present a simple non‐symmetric shape, the poly‐ellipsoid, to describe particles in discrete element simulations that incur a computational…

Abstract

Purpose

The purpose of this paper is to present a simple non‐symmetric shape, the poly‐ellipsoid, to describe particles in discrete element simulations that incur a computational cost similar to ellipsoidal particles.

Design/methodology/approach

Particle shapes are derived from joining octants of eight ellipsoids, each having different aspect ratios, across their respective principal planes to produce a compound surface that is continuous in both surface coordinate and normal direction. Because each octant of the poly‐ellipsoid is described as an ellipsoid, the mathematical representation of the particle shape can be in the form of either an implicit function or as parametric equations.

Findings

The particle surface is defined by six parameters (vs the 24 parameters required to define the eight component ellipsoids) owing to dependencies among parameters that must be imposed to create continuous intersections. Despite the complexity of the particle shapes, the particle mass, centroid and moment of inertia tensor can all be computed in closed form.

Practical implications

The particle can be implemented in any contact algorithm designed for ellipsoids with minor modifications to determine in which pair of octants the potential contact occurs.

Originality/value

The poly‐ellipsoid particle is a computational device to represent non‐spherical particles in DEM models.

Details

Engineering Computations, vol. 26 no. 6
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 21 August 2009

Paul W. Cleary

The purpose of this paper is to show how particle scale simulation of industrial particle flows using DEM (discrete element method) offers the opportunity for better…

Abstract

Purpose

The purpose of this paper is to show how particle scale simulation of industrial particle flows using DEM (discrete element method) offers the opportunity for better understanding of the flow dynamics leading to improvements in equipment design and operation.

Design/methodology/approach

The paper explores the breadth of industrial applications that are now possible with a series of case studies.

Findings

The paper finds that the inclusion of cohesion, coupling to other physics such fluids, and its use in bubbly and reacting flows are becoming increasingly viable. Challenges remain in developing models that balance the depth of the physics with the computational expense that is affordable and in the development of measurement and characterization processes to provide this expanding array of input data required. Steadily increasing computer power has seen model sizes grow from thousands of particles to many millions over the last decade, which steadily increases the range of applications that can be modelled and the complexity of the physics that can be well represented.

Originality/value

The paper shows how better understanding of the flow dynamics leading to improvements in equipment design and operation can potentially lead to large increases in equipment and process efficiency, throughput and/or product quality. Industrial applications can be characterised as large, involving complex particulate behaviour in typically complex geometries. The critical importance of particle shape on the behaviour of granular systems is demonstrated. Shape needs to be adequately represented in order to obtain quantitative predictive accuracy for these systems.

Details

Engineering Computations, vol. 26 no. 6
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 5 March 2018

Qingxiang Meng, Huanling Wang, Weiya Xu and Qiang Zhang

This paper aims to present a digital image processing (DIP)-based discrete element method (DEM) for the analysis of heterogeneous geomaterials. Taking a soil and rock…

Abstract

Purpose

This paper aims to present a digital image processing (DIP)-based discrete element method (DEM) for the analysis of heterogeneous geomaterials. Taking a soil and rock mixture as an example, the direct shear test is used to illustrate the application of this method. The numerical result is validated by the laboratory experiment and implies its feasibility in the analysis of heterogeneous geomaterials.

Design/methodology/approach

This method has two major steps. Based on a modification of the connected-component labeling algorithm, a novel vectorization method, which can transform the digital photos to vectorized geometry automatically, is proposed first. Then, a simple yet effective method for the generation of heterogeneous DEM models is presented using the simulation of simplicity technique.

Findings

DIP-DEM method is a feasible approach for the analysis of mechanical behavior of heterogeneous material. For soil and rock mixtures (SRM), the horizantal deformation at peak shear point becomes larger with the normal stress. Compared with pure soil, the rock aggregates mainly improve the friction angle of SRM.

Originality/value

As a universal method taking advantage of both DIP and DEM, this method has broad application prospects in related fields.

Details

Engineering Computations, vol. 35 no. 1
Type: Research Article
ISSN: 0264-4401

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