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About 10,000 papers for “Discrete element method”

The Discrete Element Method

Stefan Radl, Technische Universität Graz, iMooX · TUGraz OPEN Library (Graz University of Technology) · 2024

Cited by 0Open access

the Discrete Element Method

Robert James Tuley, Mark Palmer (glaxosmithkline, Robert James Tuley · 2014

Dry powder inhalers (DPI) are a common asthma treatment. Despite the number of commercial devices available, little is known about their internal operation: the process of fluidising a powder dose into an inhalation airflow. This PhD aims to investigate this process and demonstrate that it can be modelled computationally. Experimental work is described to record high speed video of the dose fluidisation from simplified DPIs. Typical DPI powders such as lactose are tested along with cohesionless glass spheres and aluminium flakes. Two distinct dose fluidisation mechanisms are identified, labelled ‘fracture ’ and ‘erosion’. Lactose exhibits a fracture mechanism – large agglomerates are produced as the powder bed cracks along lines of weakness. Glass or aluminium particles exhibit an erosion mechanism: powder is entrained into the flow as individual particles from the bed surface. The recorded video is quantitatively analysed to determine fluidisation timescales and pressures. Shear cell test results show that predicting the mechanism of fluidisation is not possible using averaged bulk powder properties. This suggests any DPI model must include the fundamental particle interactions.

Cited by 0

Rod-Bonded Discrete Element Method

K Zhang, Han Yan, Jiaming Lu et al. · Graphical Models · 2024

The Bonded Discrete Element Method (BDEM) has raised interests in the graphics community in recent years because of its good performance in fracture simulations. However, current explicit BDEM usually needs to work under very small time steps to avoid numerical instability. We propose a new BDEM, namely Rod-BDEM (RBDEM), which uses Cosserat energy and yields integrable forces and torques. We further derive a novel Cosserat rod discretization method to effectively represent the three-dimensional topological connections between discrete elements. Then, a complete implicit BDEM system integrating the appropriate fracture model and contact model is constructed using the implicit Euler integration scheme. Our method allows high Young’s modulus and larger time steps in elastic deformation, breaking, cracking, and impacting, achieving up to 8 times speed up of the total simulation.

Cited by 3Open access

Water retention in discrete element method

Yixiang Gan, Federico Maggi, Itai Einav · AIP conference proceedings · 2013

We describe water movement and retention using the discrete element method in view of future modelling of partially saturated granular materials. By defining the water potential in terms of capillary bridges at low saturation, and in terms of pressure of entrapped air at high saturation, we investigate the hysteresis of water retention in granular materials during wetting and drainage. These phenomena are successfully underpinned by our model thanks to an equation that determines the local evolution of liquid-solid contact angles at the level of pores and grains.

Cited by 0Open access

Discrete Element Method Modeling of Gas

Wenqiang Wang · AIP conference proceedings · 2002

Gaseous elements for the Discrete Element Method (DEM) modeling are presented. One distinct feature is that they have interactions even if they are separated over a large distance. The long‐range interaction presents a problem in searching neighbors and calculating interaction forces. An approach is proposed to deal with this difficulty. Using a modified DM2 code[1], several problems involving gas have been investigated. The most meaningful simulation is the problem of laser‐induced explosion damage in optical film. Results are in quantitative agreement with experimental measurements, demonstrating a unique way of studying such problems.

Cited by 0

Discrete Element Method in der Geotechnik

E. Heesen, Edwin Kreuzer · PAMM · 2007

Abstract In der Discrete Element Method (DEM) werden Böden als Granulat betrachtet, das aus einem System einzelner Partikel besteht, dieüber Kontaktkräfte miteinander in Wechselwirkung stehen und sich gegeneinander verschieben können. In dem hier verwendeten zweidimensionalen Modell werden die Partikel als konvexe unregelmäßige Polygone modelliert. Untersucht wird die Bodenmechanik im Nahfeld der Pfahlinstallation, das Fernfeld wird nicht modelliert. Es wird eine Randbedingung vorgestellt, die das Verhalten der Fernfelds adäquat wiedergibt. Bei der Modellierung zeigt sich, dass es zu deutlichen Spannungsreduktionen im umgebenden Boden kommt. Am Pfahlmantel kommt es zu starken Auflockerungen des Bodens, während andere Bodenbereiche verdichtet werden. Das Verschiebungsfeld während der Pfahlinstallation ist sehr inhomogen und instabil. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Cited by 0Open access

Discrete element method for multiscale modeling

Bruchmüller, J, Gu, S, Luo, KH et al. · UCL Discovery (University College London) · 2010

A discrete element method (DEM) has been developed to provide highly accurate and detailed predictions of the Lagrangian particle phase. Especially in this study, DEM has been used together with an Eulerian approach for the fluid phase to look at interphase exchange phenomena in a multiphase-multiscale modeling approach. The drying process inside a fluidized bed coffee bean roaster has been chosen. Herein, heat, mass, and momentum transport are solved on a fluid cell level; heat, mass, and momentum transfer coefficients are solved at a particle scale level; and 1D temperature and moisture content profiles are solved inside each coffee bean on a sub-particle scale level. Therefore, this multiscale approach provides much more information compared to existing coffee bean roaster models. In this work, a detailed description of this method is provided and results on different scale levels have been discussed. Modeling data and experimental results are compared and found to be in good agreement. © 2010 Imperial College Press.

Cited by 0

Discrete Element Method for Modeling Penetration

Plesha, Michael E. · Defense Technical Information Center (DTIC) · 2006

This research resulted in the development of the Discrete Element Method (DEM) as a general, robust, and scalable computer technique for unified modeling of the mechanical behavior of solid and particulate materials, including the transition from solid phase to particulate phase. Applications include gross damage of structures due to extreme load events, and high speed penetration of structures, involving materials such as concrete, rock, and novel combinations of these. This computer approach is useful for assessing vulnerability of military and civilian facilities such as nuclear power reactors, transportation facilities, buildings, and so on, and for assessing efficacy of military operations involving such structures. One of the primary accomplishments of this research is the development of interelement potentials for the DEM method such that accurate and convergent results are obtained.

Cited by 0

Discrete element simulations of granular pile formation: Method for calibrating discrete element models

Grima, Andrew, Wypych, Peter W · Research Online (University of Wollongong) · 2011

Purpose – The purpose of this paper is to examine several calibration techniques that have been developed to determine the discrete element method (DEM) parameters for slow and rapid unconfined flow of granular conical pile formation. This paper also aims to discuss some of the methods currently employed to scale particle properties to reduce computational resources and time to solve large DEM models.\nDesign/methodology/approach – DEM models have been calibrated against simple bench-scale experimental results to examine the validity of selected parameters for the contact, material and mechanical models to simulate the dynamic and static behaviour of cohesionless polyethylene pellets. Methods to determine quantifiable single particle parameters such as static friction and the coefficient of restitution have been highlighted. Numerical and experimental granular pile formation has been investigated using different slumping and pouring techniques to examine the dependency of the type of flow mechanism on the DEM parameters.\nFindings – The proposed methods can provide cost effective and simple techniques to determine suitable input parameters for DEM models. Rolling friction and particle shape representation has shown to have a significant influence on the bulk flow characteristics via a sensitivity analysis and needs to be accessed based on the environmental conditions.\nOriginality/value – This paper describes several effective known and novel methodologies to characterise granular materials that are needed to accurately model granular flow using the DEM to provide valuable quantitative data. For the DEM to be a viable predictive tool in industrial applications which often contain huge quantities of particles with random particle shapes and irregular properties, quick and validated techniques to “tune” DEM models are necessary.

Cited by 0

Comparison of computational fluid dynamics–discrete element method and discrete element method simulations for a screw conveyor

Shuyan Wang, Shuyan Wang, Yu Ji et al. · Asia-Pacific Journal of Chemical Engineering · 2019

Abstract Flow behavior of particles is simulated by means of discrete element method (DEM) in a screw conveyor. The gas flow is considered by the Euler model. The subgrid scale model turbulence model is applied to solve gas turbulence. A detailed description of the model equations applied has been presented. The comparison between computational fluid dynamics (CFD)‐DEM (i.e., considering gas flow) and DEM (i.e., not considering gas flow) simulation results is performed. Predicted mass flow rate with CFD‐DEM model is in better agreement with experiments by Roberts and Wills comparing with DEM results. The effects of incline angle and filling rate on the flow behavior of particles are predicted. The simulation results show that the gas flow has a major impact on particle flow behavior at a high rotation speed, whereas the velocity of particles increases with an increase of rotation speed. As the filling rate rises, both the translational granular temperature and the rotational granular particle temperature decline, which means that the particles fluctuation turns weak. While with an increase of incline angle, from the horizontal to vertical, the translational granular temperature is increased, but the rotational granular temperature reduces and then goes up. In brief, translational motion is a main mode of motion in a screw conveyor.

Cited by 11