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Author: Xiaoming Zhang
Publisher:
ISBN:
Category : Fluid dynamics
Languages : en
Pages : 0
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Book Description
The macroscopic motion of granular materials is the result of the microscopic interactions between individual particles as well as microscopic interactions with ambient fluids. Understanding the microscopic mechanism of these interactions in a multiphysics framework is therefore the key to accurately representing the micromechanical behaviors of granular materials. Among such complexities, the shape of particles plays a crucial role in the particle-particle interactions which determine the dynamic behavior of granular materials. Along with the particle shape, ambient fluids can also control particle motion through fluid-particle interactions, such as hydrodynamic and surface tension forces. However, the study on the combined effects of the particle shape and ambient fluids on particle motion is limited. This dissertation, therefore, has studied the combined effects of multiphysics and micromechanical modeling on the granular materials in different situations, such as particle flow, fluid-particle flow, and fluid-fluid-particle flow. The modeling has been achieved by coupling the computational fluid dynamics and an image-based discrete element method (CFD-iDEM), in which fluid flow is solved by the CFD, and the motion of irregular/spherical particles is updated by the iDEM. For the multiphase flow, the volume of fluid (VOF) method is applied for tracking the fluid-fluid interface, and the Continuum Surface Force (CSF) model and Continuum Capillary Force (CCF) model are used for converting the surface tension forces acting on fluids and particles into body forces, respectively. With the coupled CFD-iDEM and VOF-iDEM, various cases have been simulated to study the combined effects on the dynamic behavior of granular materials, such as particle sedimentation, particle collapse, hopper flow, particle falling into liquid, and dynamic liquid bridge between particles. The drafting, kissing and tumbling (DKT) process of the particle pairs can be affected by both the particle sphericity and roundness. The higher roundness of the particle pairs shortens the drafting stage for all orientations due to less resistance generated between the fluid and particles. The horizontal displacements of particle assemblies after collapse increase when the regularity of particles increases. The increase is milder with an ambient fluid which can both reduce the kinetic energy during the collapse and enhance the flow by lubrication during spread. The repose angle of sandpiles formed by hopper flow can be increased by more irregular particles while decreased by the ambient water. Furthermore, when one particle drops into one liquid from the air, the hydrophilic particle surface is fully covered by the wetting fluid, as opposed to the air cavity on the top of the hydrophobic particle surface. When two same spherical particles move in the opposite direction, the wetting liquid bridge rupture happens faster than the non-wetting liquid because the wetting liquid tends to adhere to the particle surface. Using all the aforementioned examples and results we showed that both the particle shape and ambient fluids play an important role in the dynamic behavior of granular materials.
Author: Xiaoming Zhang
Publisher:
ISBN:
Category : Fluid dynamics
Languages : en
Pages : 0
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Book Description
The macroscopic motion of granular materials is the result of the microscopic interactions between individual particles as well as microscopic interactions with ambient fluids. Understanding the microscopic mechanism of these interactions in a multiphysics framework is therefore the key to accurately representing the micromechanical behaviors of granular materials. Among such complexities, the shape of particles plays a crucial role in the particle-particle interactions which determine the dynamic behavior of granular materials. Along with the particle shape, ambient fluids can also control particle motion through fluid-particle interactions, such as hydrodynamic and surface tension forces. However, the study on the combined effects of the particle shape and ambient fluids on particle motion is limited. This dissertation, therefore, has studied the combined effects of multiphysics and micromechanical modeling on the granular materials in different situations, such as particle flow, fluid-particle flow, and fluid-fluid-particle flow. The modeling has been achieved by coupling the computational fluid dynamics and an image-based discrete element method (CFD-iDEM), in which fluid flow is solved by the CFD, and the motion of irregular/spherical particles is updated by the iDEM. For the multiphase flow, the volume of fluid (VOF) method is applied for tracking the fluid-fluid interface, and the Continuum Surface Force (CSF) model and Continuum Capillary Force (CCF) model are used for converting the surface tension forces acting on fluids and particles into body forces, respectively. With the coupled CFD-iDEM and VOF-iDEM, various cases have been simulated to study the combined effects on the dynamic behavior of granular materials, such as particle sedimentation, particle collapse, hopper flow, particle falling into liquid, and dynamic liquid bridge between particles. The drafting, kissing and tumbling (DKT) process of the particle pairs can be affected by both the particle sphericity and roundness. The higher roundness of the particle pairs shortens the drafting stage for all orientations due to less resistance generated between the fluid and particles. The horizontal displacements of particle assemblies after collapse increase when the regularity of particles increases. The increase is milder with an ambient fluid which can both reduce the kinetic energy during the collapse and enhance the flow by lubrication during spread. The repose angle of sandpiles formed by hopper flow can be increased by more irregular particles while decreased by the ambient water. Furthermore, when one particle drops into one liquid from the air, the hydrophilic particle surface is fully covered by the wetting fluid, as opposed to the air cavity on the top of the hydrophobic particle surface. When two same spherical particles move in the opposite direction, the wetting liquid bridge rupture happens faster than the non-wetting liquid because the wetting liquid tends to adhere to the particle surface. Using all the aforementioned examples and results we showed that both the particle shape and ambient fluids play an important role in the dynamic behavior of granular materials.
Author: Bernard Cambou
Publisher: John Wiley & Sons
ISBN: 1118623088
Category : Science
Languages : en
Pages : 263
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Book Description
Nearly all solids are compised of grains. However most studies treat materials as a continious solid. The book applies analysis used on loose granular materials to dense grainular materials. This title’s main focus is devoted to static or dynamic loadings applied to dense materials, although rapid flows and widely dispersed media are also mentioned briefly. Three essential areas are covered: Local variable analysis: Contact forces, displacements and rotations, orientation of contacting particles and fabric tensors are all examples of local variables. Their statistical distributions, such as spatial distribution and possible localization, are analyzed, taking into account experimental results or numerical simulations. Change of scales procedures: Also known as “homogenization techniques”, these procedures make it possible to construct continuum laws to be used in a continuum mechanics approach or performing smaller scale analyses. Numerical modeling: Several methods designed to calculate approximate solutions of dynamical equations together with unilateral contact and frictional laws are presented, including molecular dynamics, the distinct element method and non-smooth contact dynamics. Numerical examples are given and the quality of numerical approximations is discussed.
Author: Gianfranco Capriz
Publisher: Springer Science & Business Media
ISBN: 1461200792
Category : Technology & Engineering
Languages : en
Pages : 374
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Book Description
Soils are complex materials: they have a particulate structure and fluids can seep through pores, mechanically interacting with the solid skeleton. Moreover, at a microscopic level, the behaviour of the solid skeleton is highly unstable. External loadings are in fact taken by grain chains which are continuously destroyed and rebuilt. Many issues of modeling, even of the physical details of the phenomena, remain open, even obscure; de Gennes listed them not long ago in a critical review. However, despite physical complexities, soil mechanics has developed on the assumption that a soil can be seen as a continuum, or better yet as a medium obtained by the superposition of two and sometimes three con and the other fluids, which occupy the same portion of tinua, one solid space. Furthermore, relatively simple and robust constitutive laws were adopted to describe the stress-strain behaviour and the interaction between the solid and the fluid continua. The contrast between the intrinsic nature of soil and the simplistic engi neering approach is self-evident. When trying to describe more and more sophisticated phenomena (static liquefaction, strain localisation, cyclic mo bility, effects of diagenesis and weathering, ..... ), the nalve description of soil must be abandoned or, at least, improved. Higher order continua, incrementally non-linear laws, micromechanical considerations must be taken into account. A new world was opened, where basic mathematical questions (such as the choice of the best tools to model phenomena and the proof of the well-posedness of the consequent problems) could be addressed.
Author: Oxana Sadovskaya
Publisher: Springer Science & Business Media
ISBN: 3642290531
Category : Technology & Engineering
Languages : en
Pages : 396
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Book Description
This monograph contains original results in the field of mathematical and numerical modeling of mechanical behavior of granular materials and materials with different strengths. It proposes new models helping to define zones of the strain localization. The book shows how to analyze processes of the propagation of elastic and elastic-plastic waves in loosened materials, and constructs models of mixed type, describing the flow of granular materials in the presence of quasi-static deformation zones. In a last part, the book studies a numerical realization of the models on multiprocessor computer systems. The book is intended for scientific researchers, lecturers of universities, post-graduates and senior students, who specialize in the field of the deformable materials mechanics, mathematical modeling and adjacent fields of applied and calculus mathematics.
Author: Masao Satake
Publisher: Elsevier Publishing Company
ISBN:
Category : Granular materials
Languages : en
Pages : 392
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Book Description
This proceedings volume contains papers from researchers in Japan, the United States and England who have made fundamental contributions to the micromechanics of granular materials. The purpose of the seminar was to facilitate an exchange of ideas between scientists working with statistical and continuum theories, computer simulations and experiments on both static and dynamic behaviour. In describing the solid like behaviour of granular materials, many new ideas on the constitutive relations are introduced in this volume. As an application of the analysis, the mechanism of liquefaction is discussed. Computer simulations have become a vital tool in establishing the micromechanical approaches which otherwise would not be experimentally tested. In numerical simulations and theoretical analyses of rapid granular flow, various modifications on the nature of materials and boundaries are given. Possible applications of the techniques of the stereology and analysis based on geometrical statistics are also included. The papers collected in this volume signify that the promotion of a good understanding of the mechanics of granular materials has been and will continue to be valued in a variety of technical disciplines.
Author: Daniel Hunter Johnson
Publisher:
ISBN:
Category :
Languages : en
Pages : 116
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Book Description
Micromechanics of solid-fluid interactions can play a key role controlling macro-scale engineering behavior of granular media. The main objective of this study is to numerically investigate the micromechanics involved in solid-fluid mixtures to develop a better understanding of the macroscopic behavior of granular media for different applications. This is accomplished by developing a numerical model coupling the Discrete Element Method (DEM) and the Lattice Boltzmann Method (LBM) and employing it to study three distinct yet interrelated applications throughout the course of this research. In the first application, the DEM model is used to provide a clear relationship between energy dissipated by micro-scale mechanisms versus the traditional engineering definition based on macro-scale (continuum) parameters to develop a better understanding for the frictional behavior of granular media. Macroscopic frictional behavior of granular materials is of great importance for studying several complex problems such as fault slip and landslides. In the second application, the DEM-LBM model is employed for studying the undrained condition of dense granular media. While the majority of previous modeling approaches did not realistically represent non-uniform strain conditions that exist in geomechanical problems, including the LBM in the proposed model offers a realistic approach to simulate the undrained condition since the fluid can locally conserve the system volume. For the third application, the DEM-LBM model is used to study discontinuous shear thickening in a dense solid-fluid suspension. Shear thickening in a fluid occurs when the viscosity of the fluid increases with increasing applied strain rate. The DEM-LBM results for discontinuous shear thickening were compared to experimental data and proved to be an accurate approach at reproducing this phenomenon. The validated DEM-LBM model is then used to develop a physics-based constitutive model for discontinuous shear thickening-shear thinning in granular media-fluid suspension. A closed-form model is then calibrated using the DEM-LBM model and validated against existing experimental test results reported in the literature. Findings of this research demonstrate how micromechanical modeling can be employed to address challenging problems in granular media involving solid-fluid interaction.
Author: Qicheng Sun
Publisher: WIT Press
ISBN: 1845646444
Category : Technology & Engineering
Languages : en
Pages : 209
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Book Description
Focussing on the basic mechanics and underlying physics of granular material, Mechanics of Granular Matter starts with an introduction to contact mechanics of individual particles before moving on to a discussion of the structure of force chain networks and the influence on bulk mechanical properties of granular solids and granular flows. Furthermore, a preliminary multi scale framework is proposed for the nonlinear mechanics and strain localization in granular materials.
Author: H.H. Shen
Publisher: Elsevier
ISBN: 1483291286
Category : Technology & Engineering
Languages : en
Pages : 476
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Book Description
The 45 papers presented in this volume all share the common goal of constructing continuum models based on the micro behaviours of granular materials. Computer simulations continue to provide observations to aid modelling, while new experimental works begin to show promise for increased understanding in this area. Theoretical studies have extended into transitions between the rapid and quasi-static regimes and the fluid and solid mixture flows. Exciting new topics discussed in this volume include: concepts of a measure for randomness in quasi-static granular materials, which is analogous to the granular temperature in a rapid flow; scaling effects in granular media and their implications in both physical and computer simulations; instability; and boundary effects on heterogeneous behavior in simple flow configurations, which are posing new challenges for mathematical modelling. The volume will prove indispensable reading for researchers interested in the current developments in the fundamental aspects of mechanics of granular materials.
Author: K. Iwashita
Publisher: CRC Press
ISBN: 1000150518
Category : Study Aids
Languages : en
Pages : 408
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Book Description
This textbook compiles reports written by about 35 internationally recognized authorities, and covers a range of interests for geotechnical engineers. Topics include: fundamentals for mechanics of granular materials; continuum theory of granular materials; and discrete element approaches.
Author: Dimitrios Kolymbas
Publisher: Springer Science & Business Media
ISBN: 3642570186
Category : Science
Languages : en
Pages : 558
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Book Description
In view of its extreme complexity the mathematical description of the mechanical behaviour of granular materials is an extremely difficult task. Today many different models compete with each other. However, the complexity of the models hinders their comparison, and the potential users are confused and, often, disencouraged. This book is expected to serve as a milestone in the present situation, to evaluate the present methodes, to clear up the situation, to focus and encourage for further research activities.
