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 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.

2716 New method for considering particle shape in Discrete Element Method

2007 ◽  
Vol 2007.20 (0) ◽  
pp. 621-622
Author(s):  
Masatoshi AKASHI ◽  
Hiroshi MIO ◽  
Atsuko SHIMOSAKA ◽  
Yoshiyuki SHIRAKAWA ◽  
Jusuke HIDAKA ◽  
...  
Keyword(s):  
Discrete Element Method ◽  
Particle Shape ◽  
Discrete Element ◽  
New Method ◽  
Element Method

scholarly journals Comparison between O(n2) and O(n) neighbor search algorithm and its influence on superlinear speedup in parallel discrete element method (DEM) for complex-shaped particles

2018 ◽  
Vol 35 (6) ◽  
pp. 2327-2348 ◽  
Author(s):  
Beichuan Yan ◽  
Richard Regueiro
Keyword(s):  
Discrete Element Method ◽  
Particle Shape ◽  
Search Algorithm ◽  
Discrete Element ◽  
Search Algorithms ◽  
Content Type ◽  
Neighbor Search ◽  
Shape Complexity ◽  
Superlinear Speedup ◽  
Element Method

Purpose This paper aims to present performance comparison between O(n2) and O(n) neighbor search algorithms, studies their effects for different particle shape complexity and computational granularity (CG) and investigates the influence on superlinear speedup of 3D discrete element method (DEM) for complex-shaped particles. In particular, it aims to answer the question: O(n2) or O(n) neighbor search algorithm, which performs better in parallel 3D DEM computational practice? Design/methodology/approach The O(n2) and O(n) neighbor search algorithms are carefully implemented in the code paraEllip3d, which is executed on the Department of Defense supercomputers across five orders of magnitude of simulation scale (2,500; 12,000; 150,000; 1 million and 10 million particles) to evaluate and compare the performance, using both strong and weak scaling measurements. Findings The more complex the particle shapes (from sphere to ellipsoid to poly-ellipsoid), the smaller the neighbor search fraction (NSF); and the lower is the CG, the smaller is the NSF. In both serial and parallel computing of complex-shaped 3D DEM, the O(n2) algorithm is inefficient at coarse CG; however, it executes faster than O(n) algorithm at fine CGs that are mostly used in computational practice to achieve the best performance. This means that O(n2) algorithm outperforms O(n) in parallel 3D DEM generally. Practical implications Taking for granted that O(n) outperforms O(n2) unconditionally, complex-shaped 3D DEM is a misconception commonly encountered in the computational engineering and science literature. Originality/value The paper clarifies that performance of O(n2) and O(n) neighbor search algorithms for complex-shaped 3D DEM is affected by particle shape complexity and CG. In particular, the O(n2) algorithm outperforms the O(n) algorithm in large-scale parallel 3D DEM simulations generally, even though this outperformance is counterintuitive.

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.

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