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Author: Qiong Zhang (Mechanical engineer)
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Granular materials are ubiquitous in industrial and geophysical scenarios. At a high computational expense, the discrete element method (DEM) simulates granular materials with a high accuracy by tracking individual particles. At the other extreme, empirical formulas based on dimensional analysis and continuum models are convenient to be applied to large scale problems, but calibrations may be needed. In this thesis, DEM simulations are carried out as virtual experiments to study the particle-scale physics and then guide the formulation of empirical relations or continuum models for two applications. Dynamic similarity, commonly applied in fluid systems, has recently been extended to locomotion problems in granular media. Our previous research was limited to locomotors in cohesionless, flat beds of grains under the assumption of a simple frictional fluid rheology. However, many natural circumstances involve beds that are sloped or composed of cohesive grains. Expanded scaling relations are derived and DEM simulations are performed as validation, with inclined beds and cohesive grains using rotating "wheels" of various shape families, varying size and loading conditions. The data show a good agreement between scaled tests, suggesting the usage of these scalings as a potential design tool for off-road vehicles and extra-planetary rovers, and as an analysis tool for bio-locomotion in soils. In the bedload sediment transport process, the variability in the relation between sediment flux and driving factors is not well understood. At a given Shields number, the observed dimensionless transport rate can vary over a wide range in controlled systems. A two-way coupled fluid-grain numerical scheme has been validated against physical experiments of spherical sediment particles. It is used to explore the parameter space controlling sediment transport in simple systems. Examination of fluid-grain interactions shows fluid torque is non-negligible near the threshold. And the simulations guide the formulation of continuum models for the bedload transport and the creep flow. Furthermore, a numerical scheme has been developed to simulate the transport of natural shaped sediment particles. Conglomerated spheres, approximating the real shapes from CT scanning, are constructed in DEM and coupled with the fluid solver. Agreement with the corresponding flume experiments is observed.
Author: Qiong Zhang (Mechanical engineer)
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Granular materials are ubiquitous in industrial and geophysical scenarios. At a high computational expense, the discrete element method (DEM) simulates granular materials with a high accuracy by tracking individual particles. At the other extreme, empirical formulas based on dimensional analysis and continuum models are convenient to be applied to large scale problems, but calibrations may be needed. In this thesis, DEM simulations are carried out as virtual experiments to study the particle-scale physics and then guide the formulation of empirical relations or continuum models for two applications. Dynamic similarity, commonly applied in fluid systems, has recently been extended to locomotion problems in granular media. Our previous research was limited to locomotors in cohesionless, flat beds of grains under the assumption of a simple frictional fluid rheology. However, many natural circumstances involve beds that are sloped or composed of cohesive grains. Expanded scaling relations are derived and DEM simulations are performed as validation, with inclined beds and cohesive grains using rotating "wheels" of various shape families, varying size and loading conditions. The data show a good agreement between scaled tests, suggesting the usage of these scalings as a potential design tool for off-road vehicles and extra-planetary rovers, and as an analysis tool for bio-locomotion in soils. In the bedload sediment transport process, the variability in the relation between sediment flux and driving factors is not well understood. At a given Shields number, the observed dimensionless transport rate can vary over a wide range in controlled systems. A two-way coupled fluid-grain numerical scheme has been validated against physical experiments of spherical sediment particles. It is used to explore the parameter space controlling sediment transport in simple systems. Examination of fluid-grain interactions shows fluid torque is non-negligible near the threshold. And the simulations guide the formulation of continuum models for the bedload transport and the creep flow. Furthermore, a numerical scheme has been developed to simulate the transport of natural shaped sediment particles. Conglomerated spheres, approximating the real shapes from CT scanning, are constructed in DEM and coupled with the fluid solver. Agreement with the corresponding flume experiments is observed.
Author: Farhang Radjaï
Publisher: Wiley-ISTE
ISBN: 9781848212602
Category : Mathematics
Languages : en
Pages : 0
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Book Description
This book brings together in a single volume various methods and skills for particle-scale or discrete-element numerical simulation of granular media. It covers a broad range of topics from basic concepts and methods towards more advanced aspects and technical details applicable to the current research on granular materials. Discrete-element simulations of granular materials are based on four basic models (molecular dynamics, contact dynamics, quasi-static and event driven) dealing with frictional contact interactions and integration schemes for the equations of dynamics. These models are presented in the first chapters of the book, followed by various methods for sample preparation and monitoring of boundary conditions, as well as dimensionless control parameters. Granular materials encountered in real life involve a variety of compositions (particle shapes and size distributions) and interactions (cohesive, hydrodynamic, thermal) that have been extensively covered by several chapters. The book ends with two applications in the field of geo-materials.
Author: Stefan Luding
Publisher: Elsevier
ISBN: 0081012071
Category : Technology & Engineering
Languages : en
Pages : 150
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Book Description
Calibration and Validation of Granular Continuum Models from Particle Data: Bridging the Micro-Macro Gap reviews recent advances in the field and describes how to obtain continuum fields from particle level data. After a review of several methods, it focuses on one method, coarse-graining, and demonstrates the power of this method via various examples of granular continuum models, e.g., for shallow and segregating flows. Presents the coarse-graining method to overcome accurate result challenges by applying a local smoothing kernel with a well-defined smoothing length that automatically generates fields satisfying the continuum equations Presents a very flexible solution that can be extended to complex situations, such as two-phase flows and situations with complex external boundaries Shows readers how to apply such methods to calibrate and validate some of the most common granular flow models
Author: Debanjan Mukherjee
Publisher:
ISBN:
Category :
Languages : en
Pages : 134
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Book Description
Flowing particulate media are ubiquitous in a wide spectrum of applications that include transport systems, fluidized beds, manufacturing and materials processing technologies, energy conversion and propulsion technologies, sprays, jets, slurry flows, and biological flows. The discrete nature of the media, along with their underlying coupled multi-physical interactions can lead to a variety of interesting phenomena, many of which are unique to such media - for example, turbulent diffusion and preferential concentration in particle laden flows, and soliton like excitation patterns in a vibrated pile of granular material. This dissertation explores the utility of numerical simulations based on the discrete element method and collision driven particle dynamics methods for analyzing flowing particulate media. Such methods are well-suited to handle phenomena involving particulate, granular, and discontinuous materials, and often provide abilities to tackle complicated physical phenomena, for which pursuing continuum based approaches might be difficult or sometimes insufficient. A detailed discussion on hierarchically representing coupled, multi-physical phenomena through simple models for underlying physical interactions is presented. Appropriate physical models for mechanical contact, conductive and convective heat exchange, fluid-particle interactions, adhesive and near-field effects, and interaction with applied electromagnetic fields are presented. Algorithmic details on assembling the interaction models into a large-scale simulation framework have been elaborated with illustrations. The assembled frameworks were used to develop a computer simulation library (named `Software Library for Discrete Element Simulations' (SLIDES) for the sake of reference and continued future development efforts) and aspects of the architecture and development of this library have also been addressed. This is an object-oriented discrete particle simulation library developed in Fortran capable of performing fully 3D simulations of particulate systems. The utility and effectiveness of the developed simulation frameworks have been demonstrated using two case studies. The first study is on the analysis of the high velocity impact of stream of particles on a porous layer of material, which is a problem of interest in the analysis of erosive wear of manufactured surface coatings. The second case-study is based on the deposition of flowing particulate spray on a target surface, which is a problem of interest in the analysis of particulate deposition-based manufacturing processes. In both cases, the aspect of extracting important information on system behavior from the collective dynamics of the particulate media has been outlined. For the first case, this involved a characterization of material damage due to impact generated stresses, and for the second case, this involved analysis of adhesion and deposited coating properties.
Author: Thorsten Pöschel
Publisher: Springer Science & Business Media
ISBN: 354027720X
Category : Science
Languages : en
Pages : 324
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Book Description
Computer simulations not only belong to the most important methods for the theoretical investigation of granular materials, but provide the tools that have enabled much of the expanding research by physicists and engineers. The present book is intended to serve as an introduction to the application of numerical methods to systems of granular particles. Accordingly emphasis is on a general understanding of the subject rather than on the presentation of latest advances in numerical algorithms. Although a basic knowledge of C++ is needed for the understanding of the numerical methods and algorithms in the book, it avoids usage of elegant but complicated algorithms to remain accessible for those who prefer to use a different programming language. While the book focuses more on models than on the physics of granular material, many applications to real systems are presented.
Author: Keng-Wit Lim
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
This dissertation is concerned with the development of a new discrete element method (DEM) based on Non-Uniform Rational Basis Splines (NURBS). With NURBS, the new DEM is able to capture sphericity and angularity, the two particle morphological measures used in characterizing real grain geometries. By taking advantage of the parametric nature of NURBS, the Lipschitzian dividing rectangle (DIRECT) global optimization procedure is employed as a solution procedure to the closest-point projection problem, which enables the contact treatment of non-convex particles. A contact dynamics (CD) approach to the NURBS-based discrete method is also formulated. By combining particle shape flexibility, properties of implicit time-integration, and non-penetrating constraints, we target applications in which the classical DEM either performs poorly or simply fails, i.e., in granular systems composed of rigid or highly stiff angular particles and subjected to quasistatic or dynamic flow conditions. The CD implementation is made simple by adopting a variational framework, which enables the resulting discrete problem to be readily solved using off-the-shelf mathematical programming solvers. The capabilities of the NURBS-based DEM are demonstrated through 2D numerical examples that highlight the effects of particle morphology on the macroscopic response of granular assemblies under quasistatic and dynamic flow conditions, and a 3D characterization of material response in the shear band of a real triaxial specimen.
Author: Catherine O'Sullivan
Publisher: CRC Press
ISBN: 1482266490
Category : Technology & Engineering
Languages : en
Pages : 574
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Book Description
The first single work on DEM providing the information to get started with this powerful numerical modelling approach. Provides the basic details of the numerical method and the approaches used to interpret the results of DEM simulations. It will be of use to professionals, researchers and higher level students, with a theoretical overview of DEM as well as practical guidance.Selected Contents: 1.Introduction 2.Use of DEM in Geomechanics 3.Calculation of Contact Forces 4.Particle Motion 5.Particle Types 6.Boundary Conditions 7.Initial Geometry and Specimen Generation 8.Time Integration and Discrete Element Modelling 9.DEM Interpretation: A Continuum Perspective 10.Postprocessing: Graphical Interpretation of DEM Simulations 11.Basic Statisti
Author: Vidyapati
Publisher:
ISBN:
Category :
Languages : en
Pages : 168
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Book Description
Author: Benjamin K. Cook
Publisher:
ISBN:
Category : Mathematics
Languages : en
Pages : 448
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Book Description
Proceedings of the Third International Conference on Discrete Element Methods, held in Santa Fe, New Mexico on September 23-25, 2002. This Geotechnical Special Publication contains 72 technical papers on discrete element methods (DEM), a suite of numerical techniques developed to model granular materials, rock, and other discontinua at the grain scale. Topics include: DEM formulation and implementation approaches, coupled methods, experimental validation, and techniques, including three-dimensional particle representations, efficient contact detection algorithms, particle packing schemes, and code design. Coupled methods include approaches to linking solid continuum and fluid models with DEM to simulate multiscale and multiphase phenomena. Applications include fundamental investigations of granular mechanics; micromechanical studies of powder, soil, and rock behavior; and large-scale modeling of geotechnical, material processing, mining, and petroleum engineering problems.
Author: Peter Wriggers
Publisher: Springer Science & Business Media
ISBN: 3211772987
Category : Science
Languages : en
Pages : 252
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Book Description
Topics of this book span the range from spatial and temporal discretization techniques for contact and impact problems with small and finite deformations over investigations on the reliability of micromechanical contact models over emerging techniques for rolling contact mechanics to homogenization methods and multi-scale approaches in contact problems.
