A Numerical Study on the Sensitivity of the Discrete Element Method for Hopper Discharge

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
H. Kruggel-Emden ◽  
S. Rickelt ◽  
S. Wirtz ◽  
V. Scherer
Keyword(s):  
Discrete Element Method ◽  
Numerical Study ◽  
Discrete Element ◽  
Tangential Direction ◽  
Flow Properties ◽  
Friction Coefficients ◽  
Flow Rates ◽  
Design Variables ◽  
Side Walls ◽  
Element Method

Based on the time-driven discrete element method, granular flow within a hopper is investigated. The main focus is thereby set on hopper vessel design variables such as discharge rates and applied wall pressures. Within the used model contacts are assumed as linear viscoelastic in normal and frictional-elastic in tangential direction. The hopper geometry is chosen according to Yang and Hsiau (2001, “The Simulation and Experimental Study of Granular Materials Discharged From a Silo With the Placement of Inserts,” Powder Technol., 120(3), pp. 244–255), who performed both experimental and numerical investigations. The considered setup is attractive because it involves only a small number of particles enabling fast modeling. However, the results on the experimental flow rates reported are contradictory and are afflicted with errors. By an analysis of the hopper fill levels at different points of time, the correct average discharge times and flow rates are obtained. Own simulation results are in good agreement with the experimental flow rates and discharge times determined. Based on the thereby defined set of simulation parameters, a sensitivity analysis of parameters such as friction coefficients, stiffnesses, and time steps is performed. As flow properties, besides the overall discharge times, the discharge time averaged axial and radial velocity distributions within the hopper and the normal stresses on the side walls during the first seconds of discharge are considered. The results show a strong connection of the friction coefficients with the discharge times, the velocity distributions, and the stresses on the side walls. Other parameters only reveal a weak often indifferent influence on the studied flow properties.

A Numerical Study on the Sensitivity of the Discrete Element Method: The Multi Particle Perspective

2008 ◽  
Author(s):  
Harald Kruggel-Emden ◽  
Stefan Rickelt ◽  
Siegmar Wirtz ◽  
Viktor Scherer
Keyword(s):  
Discrete Element Method ◽  
Visual Analysis ◽  
Numerical Study ◽  
Discrete Element ◽  
Tangential Direction ◽  
Flow Properties ◽  
Friction Coefficients ◽  
Flow Rates ◽  
Simulation Parameters ◽  
Element Method

Based on the time-driven Discrete Element Method, granular flow within a hopper is investigated. Contacts are assumed as linear viscoelastic in normal and frictional-elastic in tangential direction. The hopper geometry is chosen according to Yang and Hsiau [1] who performed both experimental and numerical investigations. The considered setup is attractive, because it involves only a small number of particles enabling fast modeling. However, results on the experimental flow rates reported are contradictory and are afflicted with errors. By a visual analysis of the hopper fill levels at different points of time the correct average discharge times and flow rates are obtained. Own simulation results are in good agreement with the experimental flow rates and discharge times determined. Based on the thereby defined set of simulation parameters, a sensitivity analysis of parameters like friction coefficients, stiffnesses and time steps is performed. As flow properties, besides the overall discharge times, the time averaged axial and radial velocity distributions within the hopper are considered. Results show a strong connection of the friction coefficients with the discharge times and the velocity distributions. Other parameters only reveal a weak often indifferent influence on the studied flow properties.

Numerical study of sheared mobile polydisperse sediment beds with a coupled lattice Boltzmann - discrete element method

2021 ◽  
Author(s):  
Christoph Rettinger ◽  
Sebastian Eibl ◽  
Ulrich Rüde ◽  
Bernhard Vowinckel
Keyword(s):  
Discrete Element Method ◽  
Lattice Boltzmann ◽  
Numerical Study ◽  
Experimental Studies ◽  
Discrete Element ◽  
Parallel Execution ◽  
Coupling Mechanism ◽  
Size Segregation ◽  
Minimum Diameter ◽  
Element Method

<p>With the increasing computational power of today's supercomputers, geometrically fully resolved simulations of particle-laden flows are becoming a viable alternative to laboratory experiments. Such simulations enable detailed investigations of transport phenomena in various multiphysics scenarios, such as the coupled interaction of sediment beds with a shearing fluid flow. There, the majority of available simulations as well as experimental studies focuses on setups of monodisperse particles. In reality, however, polydisperse configurations are much more common and feature unique effects like vertical size segregation.</p><p>In this talk, we will present numerical studies of mobile polydisperse sediment beds in a laminar shear flow, with a ratio of maximum to minimum diameter up to 10. The lattice Boltzmann method is applied to represent the fluid dynamics through and above the sediment bed efficiently. We model particle interactions by a discrete element method and explicitly account for lubrication forces. The fluid-particle coupling mechanism is based on the geometrically fully resolved momentum transfer between the fluid and the particulate phase. We will highlight algorithmic aspects and communication schemes essential for massively parallel execution.</p><p>Utilizing these capabilities allows us to achieve large-scale simulations with more than 26.000 densely-packed polydisperse particles interacting with the fluid. With this, we are able to reproduce effects like size segregation and to study the rheological behavior of such systems in great detail. We will evaluate and discuss the influence of polydispersity on these processes. These insights will be used to improve and extend existing macroscopic models.</p>

Numerical Study of Particle Behaviour in Split-Flow Thin-Channel Fractionation Using the Discrete Element Method

2008 ◽  
Vol 43 (11-12) ◽  
pp. 2981-3002 ◽  
Author(s):  
Myhuong Nguyen ◽  
Martin Rhodes ◽  
Kurt Liffman ◽  
Ian McKinnon ◽  
Ron Beckett
Keyword(s):  
Discrete Element Method ◽  
Numerical Study ◽  
Discrete Element ◽  
Split Flow ◽  
Thin Channel ◽  
Particle Behaviour ◽  
Element Method

Experimental and Numerical Study of Railway Ballast Compactness during Tamping Process

2013 ◽  
Vol 690-693 ◽  
pp. 2730-2733
Author(s):  
Tao Yong Zhou ◽  
Bin Hu ◽  
Bo Yan ◽  
Jun Feng Sun
Keyword(s):  
Discrete Element Method ◽  
Numerical Study ◽  
Discrete Element ◽  
Railway Track ◽  
Analysis Model ◽  
Railway Ballast ◽  
Element Analysis ◽  
Before And After ◽  
Filling Method ◽  
Element Method

Railway ballast tamping operations is employed in order to restore the geometry of railway track distorted by train traffics. The main goal is to compact the stone ballast under the sleepers supporting the railway squeezing and vibrations. The ballast compactness is the most direct index for evaluating the effect of tamping operation. This paper presents an experimental method used to detect the railway ballast compactness before and after tamping operation based on water-filling method, and creates a discrete element analysis model of railway ballast which analyzes the change of ballast compactness before and after tamping operation based on discrete element method. The simulation results are very similar with experimental results, which verify that the discrete element method is an effective method to evaluate the change of railway ballast compactness during tamping process.

scholarly journals A Numerical Study of Railway Ballast Subjected to Direct Shearing Using the Discrete Element Method

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Hongyi Zhao ◽  
Jing Chen
Keyword(s):  
Discrete Element Method ◽  
Mechanical Performance ◽  
Numerical Study ◽  
Discrete Element ◽  
Contact Forces ◽  
Angle Of Repose ◽  
Particle Rotation ◽  
Railway Ballast ◽  
Depth Analysis ◽  
Element Method

Railway ballast is a coarse granular material used to carry train loads and provide drainage for the rail tracks. This study presents numerical explorations of the mechanical performance of ballast aggregates subjected to direct shear tests. The discrete element method (DEM) was used to investigate the microscopic characteristics of ballast aggregates during shearing while considering contact distribution, particle rotation, and particle displacement. By testing the angle of repose of ballast aggregates, the parameters for the DEM contact model could be calibrated. Four specimens were prepared and then subjected to different normal pressures. The results show that the contact between ballast particles intensifies in terms of the amount and magnitude as the normal pressure increases. A Fourier analysis was applied to investigate the anisotropy of contact normal and the contact forces for ballast aggregates at different shearing phases. The rotational and translational movements of ballast particles were investigated, and this investigation revealed that particle rotation gradually increased as the shearing propagated. Four regions in the aggregates were identified according to the translational pattern of ballast particles. The results of this research provide an in-depth analysis of microscopic characteristics from a particulate scale.

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