Particle Size Segregation In Dense Granular Flows
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Particle Size Segregation In Dense Granular Flows
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Author : Kasper Van der Vaart
language : en
Publisher:
Release Date : 2016
Particle Size Segregation In Dense Granular Flows written by Kasper Van der Vaart and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
Mots-clés de l'auteur: Granular flows ; Particle-size segregation ; Particle-scale dynamics ; Non-intrusive imaging ; Asymmetric behaviour.
Modelling Size Segregation In Dense Granular Flows
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Author : Parmesh Gajjar
language : en
Publisher:
Release Date : 2016
Modelling Size Segregation In Dense Granular Flows written by Parmesh Gajjar and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
Particle Size Segregation And Rheology Of Geophysical Granular Flows
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Author : James Baker
language : en
Publisher:
Release Date : 2017
Particle Size Segregation And Rheology Of Geophysical Granular Flows written by James Baker and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.
Flow Dynamics And Segregation Of Dry Granular Materials And Slurries
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Author : Nitin Jain
language : en
Publisher:
Release Date : 2004
Flow Dynamics And Segregation Of Dry Granular Materials And Slurries written by Nitin Jain and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2004 with categories.
Granular flows and segregation are important in a wide range of industrial and geological situations varying from mixing powders and formulation for pharmaceutical industries to landslides. The goal of this work is to better understand both the flow dynamics and the segregation in granular materials using a prototypical system---a quasi-2D rotating tumbler. Both dry granular matter and wet granular matter (slurries) are considered. Particle Image Velocimetry (PIV) coupled with Particle Tracking Velocimetry (PTV) is used to measure the dynamics in the flowing layer to investigate the effect of the interstitial fluid. Under slurry conditions the flowing layer thickness and the angle of repose are higher than the dry counterpart for the same sized beads tumbled at the same angular velocity. However, the surface velocity and shear rate are smaller when the interstitial fluid is a liquid rather than air. The velocity profile is nearly linear throughout the layer except for a region near the fixed bed where the velocity profile is logarithmic. Experiments on granular segregation in a circular tumbler reveal that for particle size and density combinations where percolation and buoyancy both contribute to segregation, either radial streaks or a "classical" core can occur, depending on the particle size ratio. Mixing is observed instead of segregation when the denser beads are larger than the lighter beads so that the ratio of particle sizes is greater than the ratio of particle densities. Changes in the tumbler shape introduce chaos in the system and causes segregation patterns to differ significantly in shape. Regardless of the differences in the shape of segregation pattern for these tumblers, the final mixing efficiency predominantly depends on the particle parameters.
Granular Media
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Author : Bruno Andreotti
language : en
Publisher: Cambridge University Press
Release Date : 2013-06-13
Granular Media written by Bruno Andreotti and has been published by Cambridge University Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013-06-13 with Science categories.
Provides the state-of-the-art of the physics of granular media for graduate students and researchers in physics, applied mathematics and engineering.
Mutiscale Modeling Of Segregation In Granular Flows
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Author :
language : en
Publisher:
Release Date : 2007
Mutiscale Modeling Of Segregation In Granular Flows written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with categories.
Modeling and simulation of segregation phenomena in granular flows are investigated. Computational models at different scales ranging from particle level (microscale) to continuum level (macroscale) are employed in order to determine the important microscale physics relevant to macroscale modeling. The capability of a multi-fluid model to capture segregation caused by density difference is demonstrated by simulating grain-chaff biomass flows in a laboratory-scale air column and in a combine harvester. The multi-fluid model treats gas and solid phases as interpenetrating continua in an Eulerian frame. This model is further improved by incorporating particle rotation using kinetic theory for rapid granular flow of slightly frictional spheres. A simplified model is implemented without changing the current kinetic theory framework by introducing an effective coefficient of restitution to account for additional energy dissipation due to frictional collisions. The accuracy of predicting segregation rate in a gas-fluidized bed is improved by the implementation. This result indicates that particle rotation is important microscopic physics to be incorporated into the hydrodynamic model. Segregation of a large particle in a dense granular bed of small particles under vertical. vibration is studied using molecular dynamics simulations. Wall friction is identified as a necessary condition for the segregation. Large-scale force networks bearing larger-than-average forces are found with the presence of wall friction. The role of force networks in assisting rising of the large particle is analyzed. Single-point force distribution and two-point spatial force correlation are computed. The results show the heterogeneity of forces and a short-range correlation. The short correlation length implies that even dense granular flows may admit local constitutive relations. A modified minimum spanning tree (MST) algorithm is developed to asymptotically recover the force statistics in the force networks. This algorithm provides a possible route to constructing a continuum model with microstructural information supplied from it. Microstructures in gas fluidized beds are also analyzed using a hybrid method, which couples the discrete element method (DEM) for particle dynamics with the averaged two-fluid (TF) equations for the gas phase. Multi-particle contacts are found in defluidized regions away from bubbles in fluidized beds. The multi-particle contacts invalidate the binary-collision assumption made in the kinetic theory of granular flows for the defluidized regions. Large ratios of contact forces to drag forces are found in the same regions, which confirms the relative importance of contact forces in determining particle dynamics in the defluidized regions.
Calibration And Validation Of Granular Continuum Models From Particle Data
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Author : Thomas Weinhart
language : en
Publisher: ISTE Press - Elsevier
Release Date : 2018-09-15
Calibration And Validation Of Granular Continuum Models From Particle Data written by Thomas Weinhart and has been published by ISTE Press - Elsevier this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018-09-15 with Technology & Engineering categories.
Calibration and Validation of Granular Continuum Models from Particle Data: Bridging the Micro-Macro Gap explains how to calibrate and/or validate granular continuum models from experimental or numerical data using micro-macro transition methods that are required to obtain continuum fields (such as density, momentum and stress) from particle data (positions, velocities and forces). This is especially challenging for non-uniform and dynamic situations. This book reviews recent advances in this field and describes how to obtain continuum fields from particle level data. After reviewing several methods, it focuses on coarse-graining, demonstrating the power of this particular method via various examples. 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 Provides 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 calibrate and validate some of the most common granular flow models
Iutam Symposium On Segregation In Granular Flows
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Author : Anthony D. Rosato
language : en
Publisher: Springer Science & Business Media
Release Date : 2013-04-17
Iutam Symposium On Segregation In Granular Flows written by Anthony D. Rosato and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013-04-17 with Technology & Engineering categories.
Segregation is a pervasive phenomenon whereby a flowing granular mass consisting of particles with diverse physical properties becomes spatially inhomogeneous. In the industrial sector that deals with the handling and processing of bulk solids, this non-uniformity is highly undesirable since blend homogeneity is generally a stringent requirement of most products. In the arena of geophysical flows, segregation can enhance the destructive capabilities of natural events such as avalanches and landslides. During the last 15 years, these issues have provided motivation and fostered collaborations between the communities of mathematicians, engineers, industrial researchers, and physicists to develop predictive models of segregation by integrating the perspectives and approaches of each. The collection of unique papers brings to light many of the perplexing scientific and technical issues in our current understanding of this complex phenomenon. It addresses advances in experiment, computational modeling and theory. This volume is one of the very few books devoted entirely to problems of segregation of particulate solids.
Experimental Investigation Of Particle Segregation In Hopper Discharge
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Author : Byung-Hwan Chu
language : en
Publisher:
Release Date : 2008
Experimental Investigation Of Particle Segregation In Hopper Discharge written by Byung-Hwan Chu and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with categories.
ABSTRACT: Many industrial processes including food, mining, and pharmaceuticals involve handling mixtures of granular materials. The tendency of granular materials to segregate due to differences in particle properties such as, size, shape, and density negatively affects the process efficiency and product quality. Our study focused on segregation of particles in hopper flow with the following conditions: well-mixed initial fill, funnel flow, and cylindrical hopper geometry. Glass beads and steel shots in three particle sizes each are used to investigate the effect of size ratio and density difference on particle segregation. Also, to study the effect of particle shape on segregation of particles, crushed glass in two sizes is used. Results show that size-segregation patterns are initially fines-rich and then fines-depleted at the end of discharge. Segregation increases for larger particle size ratios and decreases for fines fractions that are above 10%. The extent of segregation for mixtures of crushed glasscrushed glass is not significantly different from spherical glass mixtures. Given the same size ratio, mixtures consisting of smaller particles show less segregation. The segregation trend due to density effects is initially rich in particles with the higher density and then rich in the particles with the lower density at the end of the discharge.
Granular Flow Segregation And Agglomeration In Bladed Mixers
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Author : Brenda Remy
language : en
Publisher:
Release Date : 2010
Granular Flow Segregation And Agglomeration In Bladed Mixers written by Brenda Remy and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with Granular materials categories.
A large number of industrial processes involve the transport, mixing and storage of particulate systems. While prevalent in industry, particulate processes are commonly plagued by problems due to the complex rheology of these systems. In this work, the behavior of granular materials in a bladed mixer, an industrially relevant geometry, was investigated using computational and experimental techniques. Experimental flows were characterized via Particle Image Velocimetry and image analysis. Discrete element simulations were carried out to examine the effect of a wide range of system parameters. Particulate flows in bladed mixers were found to be periodic with complex flow patterns developing throughout the particle bed. Cohesionless flows were initially studied. For monodisperse flows, two distinct flow regimes were observed: a quasi-static regime where blade speed provides the time scale for momentum transfer and an intermediate regime where stresses scale linearly with blade speed. Particle and wall roughness were found to significantly affect bladed mixer flows. Systems with higher roughness are characterized by enhanced particle motion and mixing. Simple scaling relationships were observed for monodisperse flows in the quasi-static regime. Particle velocities and diffusivities were found to scale linearly with mixer size and blade speed, while stresses scaled linearly with particle bed weight. In polydisperse flows, size segregation was found to occur due to sieving. However, it was found that the extent of segregation can be reduced by introducing intermediate particle sizes in between the smallest and largest particles. Finally, wet particle flows were examined. At low moisture contents, enhanced particle velocities and mixing kinetics were observed in comparison to dry flows. However, at higher moisture contents, particle velocities and mixing rates were observed to decrease. Wet particle flows were characterized by the formation of particle agglomerates. Agglomerate formation led to an increase in particle bed roughness which significantly influenced macroscopic and microscopic flow properties. These findings contribute to the understanding of granular behavior in complex systems. Improved understanding of granular flows will enable the development of first-principles based models which can assist in the design and scale-up of bladed mixer operations and the identification of critical processes parameters.