Computational study of granular shear flows of dry flexible fibres using the discrete element method

2015 ◽  
Vol 775 ◽  
pp. 24-52 ◽  
Author(s):  
Y. Guo ◽  
C. Wassgren ◽  
B. Hancock ◽  
W. Ketterhagen ◽  
J. Curtis
Keyword(s):  
Discrete Element Method ◽  
Shear Flows ◽  
Volume Fraction ◽  
Solid Phase ◽  
Computational Study ◽  
Solid Volume Fraction ◽  
Discrete Element ◽  
Effective Coefficients ◽  
Phase Stresses ◽  
Element Method

In this study, shear flows of dry flexible fibres are numerically modelled using the discrete element method (DEM), and the effects of fibre properties on the flow behaviour and solid-phase stresses are explored. In the DEM simulations, a fibre is formed by connecting a number of spheres in a straight line using deformable and elastic bonds. The forces and moments induced by the bond deformation resist the relative normal, tangential, bending and torsional movements between two bonded spheres. The bond or deforming stiffness determines the flexibility of the fibres and the bond damping accounts for the energy dissipation in the fibre vibration. The simulation results show that elastically bonded fibres have smaller effective coefficients of restitution than rigidly connected fibres. Thus, smaller solid-phase stresses are obtained for flexible fibres, particularly with bond damping, compared with rigid fibres. Frictionless fibres tend to align with a small angle from the flow direction as the solid volume fraction increases, and fibre deformation is minimized due to the alignment. However, jamming, with a corresponding sharp stress increase, large fibre deformation and dense contact force network, occurs for fibres with friction at high solid volume fractions. It is also found that jamming is more prevalent in dense flows with larger fibre friction coefficient, rougher surface, larger stiffness and larger aspect ratio.

scholarly journals Discrete Element Method Investigation of Binary Granular Flows with Different Particle Shapes

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1841
Author(s):  
Yi Liu ◽  
Zhaosheng Yu ◽  
Jiecheng Yang ◽  
Carl Wassgren ◽  
Jennifer Sinclair Curtis ◽  
...  
Keyword(s):  
Discrete Element Method ◽  
Binary Mixtures ◽  
Particle Shape ◽  
Shear Flows ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Discrete Element ◽  
Particle Interactions ◽  
Particle Alignment ◽  
Element Method

The effects of particle shape differences on binary mixture shear flows are investigated using the Discrete Element Method (DEM). The binary mixtures consist of frictionless rods and disks, which have the same volume but significantly different shapes. In the shear flows, stacking structures of rods and disks are formed. The effects of the composition of the mixture on the stacking are examined. It is found that the number fraction of stacking particles is smaller for the mixtures than for the monodisperse rods and disks. For binary mixtures with small particle shape differences, the mixture stresses are bounded by the stresses of the two corresponding monodisperse systems. However, for binary mixtures with large particle shape differences, the stresses of the mixtures can be larger than the stresses of the monodisperse systems at large solid volume fractions because larger differences in particle shape cause geometrical interference in packing, leading to stronger particle–particle interactions in the flow. The stresses in dense binary mixtures are found to be exponential functions of the order parameter, which is a measure of particle alignment. Based on the simulation results, an empirical expression for the bulk friction coefficient (ratio of the shear stress to normal stress) for dense binary flows is proposed by accounting for the effects of particle alignment and solid volume fraction.

Computational Study of Slurry Flow in Pipes to Determine Profiles Sensed in Near Infrared Slurry Measurements

2011 ◽  
Author(s):  
V. Pasangulapati ◽  
N. R. Kesana ◽  
G. Sharma ◽  
F. W. Chambers ◽  
M. E. McNally ◽  
...  
Keyword(s):  
Near Infrared ◽  
Volume Fraction ◽  
Solid Phase ◽  
Computational Study ◽  
Solid Volume Fraction ◽  
Density Ratio ◽  
Optical Measurements ◽  
Concentration Profiles ◽  
Horizontal Pipe ◽  
Volume Fractions

It is desired to perform accurate Near Infrared sensor measurements of slurries flowing in pipes leaving large batch reactors. A concern with these measurements is the degree to which the slurry sensed is representative of the material in the reactor and flowing through the pipe. Computational Fluid Dynamics (CFD) has been applied to the flow in the pipe to determine the flow fields and the concentration profiles seen by the sensors. The slurry was comprised of a xylene liquid phase and an ADP (2-amino-4, 6-dimethylpyrimidine) solid phase with a density ratio of 1.7. Computations were performed for a horizontal pipe with diameter 50.8 mm, length 2.032 m, and 1.76 m/s and 3.26 m/s mixture velocities. The corresponding pipe Reynolds numbers were 1.19E+05 and 2.21E+05. The flow through a slotted cylindrical probe inserted radially in the pipe also was considered. Spherical slurry particles with diameters from 10 μm to 1000 μm were considered with solid volume fractions of 12%, 24%, and 35%. Computations were performed with ANSYS FLUENT 12 software using the Realizable k-ε turbulence model and the enhanced wall treatment function. Comparisons of computed vertical profiles of solid volume fraction to results in the literature showed good agreement. Symmetric, nearly flat solid volume fraction profiles were observed for 38 μm particles for all three initial solid volume fractions. Asymmetric solid volume fraction profiles with greater values toward the bottom were observed for the larger particles. Changes in the profiles of turbulent kinetic energy also were observed. These changes are important for optical measurements which depend upon the mean concentration profiles as well as the turbulent motion of the slurry particles.

scholarly journals Semi-Autogenous Wet Grinding Modeling With CFD-DEM

Minerals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 485
Author(s):  
Vladislav Lvov ◽  
Leonid Chitalov
Keyword(s):  
Discrete Element Method ◽  
Solid Phase ◽  
Discrete Element ◽  
Primary Phase ◽  
Secondary Phases ◽  
Interaction Coefficients ◽  
Ansys Fluent ◽  
Euler Model ◽  
Linear Spring ◽  
Element Method

The paper highlights the features of constructing a model of a wet semi-autogenous grinding mill based on the discrete element method and computational fluid dynamics. The model was built using Rocky DEM (v. 4.4.2, ESSS, Brazil) and Ansys Fluent (v. 2020 R2, Ansys, Inc., United States) software. A list of assumptions and boundary conditions necessary for modeling the process of wet semi-autogenous grinding by the finite element method is presented. The created model makes it possible to determine the energy-coarseness ratios of the semi-autogenous grinding (SAG) process under given conditions. To create the model in Rocky DEM the following models were used: The Linear Spring Rolling Limit rolling model, the Hysteretic Linear Spring model of the normal interaction forces and the Linear Spring Coulomb Limit for tangential forces. When constructing multiphase in Ansys Fluent, the Euler model was used with the primary phase in the form of a pulp with a given viscosity and density, and secondary phases in the form of air, crushing bodies and ore particles. The resistance of the solid phase to air and water was described by the Schiller–Naumann model, and viscosity by the realizable k-epsilon model with a dispersed multiphase turbulence model. The results of the work methods for material interaction coefficients determination were developed. A method for calculating the efficiency of the semi-autogenous grinding process based on the results of numerical simulation by the discrete element method is proposed.

Discrete Element Method for Modeling Penetration

2004 ◽  
Author(s):  
Federico A. Tavarez ◽  
Michael E. Plesha
Keyword(s):  
Discrete Element Method ◽  
Solid Phase ◽  
Bulk Material ◽  
Discrete Element ◽  
Test Problems ◽  
Careful Study ◽  
Specific Test ◽  
Element Size ◽  
Seamless Transition ◽  
Element Method

The Discrete Element Method (DEM) discretizes a material using rigid elements of simple shape. Each element interacts with neighboring elements through appropriate interaction laws. The number of elements is typically large and is limited by computer speed. The method has seen widespread applications to modeling particulate media and more recently to modeling solids such as concrete, ceramic, and metal. For problems with severe damage, DEM offers a number of attractive features over continuum based numerical methods, with the primary feature being a seamless transition from solid phase to particulate phase. This study illustrates the potential of DEM for modeling penetration and briefly points out its numerous advantages. A weakness of DEM is that its convergence properties are not understood. The crucial question is whether convergence is obtained as DEM element size vanishes in the limit of model refinement. The major focus of our investigation will be a careful study of convergence for modeling the degradation of a solid into fragments. Our results show that indeed convergence is obtained in several specific test problems. Moreover, elastic interelement stiffness and damping properties were proven to be particle size-independent. However, convergence in material failure due to crack growth is obtained only if the interparticle potentials are properly constructed as functions of DEM element size and bulk material properties such as elastic modulus and fracture toughness.

scholarly journals Unresolved CFD and DEM Coupled Solver for Particle-Laden Flow and Its Application to Single Particle Settlement

2020 ◽  
Vol 8 (12) ◽  
pp. 983
Author(s):  
Seongjin Song ◽  
Sunho Park
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Discrete Element Method ◽  
Open Source ◽  
Single Particle ◽  
Volume Expansion ◽  
Volume Fraction ◽  
Discrete Element ◽  
Water Tank ◽  
Element Method

In the present study, a single particle settlement was studied using a developed unresolved computational fluid dynamics (CFD) and discrete element method (DEM) coupling solver. The solver was implemented by coupling OpenFOAM, the open-source computational fluid dynamics libraries, with LIGGGHTS, the open-source discrete element method libraries. An averaging method using a kernel function was considered to decrease the grid dependency. For the drag model of a single particle, a revised volume fraction with a particle volume expansion coefficient was applied. Falling particles in a water tank were simulated and compared with the empirical correlation. A parametric study using several integrated added mass coefficients and volume expansion coefficients from low to high Reynolds numbers was carried out. The simulations which used the developed numerical methods showed significantly improved predictions of particle settlement.

Investigation on the uneven distribution of different types of ores in the hopper and stock surface during the charging process of blast furnace based on discrete element method

2019 ◽  
Vol 116 (3) ◽  
pp. 314 ◽  
Author(s):  
Wenxuan Xu ◽  
Shusen Cheng ◽  
Qun Niu ◽  
Wei Hu ◽  
Jiawen Bang
Keyword(s):  
Blast Furnace ◽  
Discrete Element Method ◽  
Volume Fraction ◽  
Discrete Element ◽  
Peripheral Region ◽  
Volume Distribution ◽  
Intermediate Region ◽  
Different Types ◽  
Stock Surface ◽  
Element Method

The model of an actual 4070 m3 bell-less top blast furnace with two parallel hoppers was established, and the distribution of the sinter, pellet, and lump ore in the hopper and the stock surface was analyzed based on the discrete element method. The results show that the distribution of different types of ores is not uniform in the hopper already. In the radial direction of the stock surface, the sinter volume fraction in the center and peripheral region of the stock surface is higher than that in the intermediate region of the stock surface, but the volume distribution of the pellet and lump ore is opposite to the sinter volume distribution. Owing to the size of lump ore is small, so the pressure drop of burden layer in the intermediate region of the stock surface is larger than that in the center and peripheral region. In the circumferential direction of the stock surface, the standard deviation of the volume distribution of the sinter, pellet, and lump ore is 1.28, 0.92 and 0.49, respectively.

Discrete element method to model cracking for two layer systems

TAPPI Journal ◽  
2019 ◽  
Vol 18 (2) ◽  
pp. 101-108
Author(s):  
Daniel Varney ◽  
Douglas Bousfield
Keyword(s):  
Discrete Element Method ◽  
Flexural Modulus ◽  
Single Layer ◽  
Discrete Element ◽  
Flexural Stress ◽  
Layer System ◽  
Three Point Bending ◽  
Moving Force ◽  
Coating Layers ◽  
Element Method

Cracking at the fold is a serious issue for many grades of coated paper and coated board. Some recent work has suggested methods to minimize this problem by using two or more coating layers of different properties. A discrete element method (DEM) has been used to model deformation events for single layer coating systems such as in-plain and out-of-plain tension, three-point bending, and a novel moving force picking simulation, but nothing has been reported related to multiple coating layers. In this paper, a DEM model has been expanded to predict the three-point bending response of a two-layer system. The main factors evaluated include the use of different binder systems in each layer and the ratio of the bottom and top layer weights. As in the past, the properties of the binder and the binder concentration are input parameters. The model can predict crack formation that is a function of these two sets of factors. In addition, the model can predict the flexural modulus, the maximum flexural stress, and the strain-at-failure. The predictions are qualitatively compared with experimental results reported in the literature.

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