Discrete element methods

Lewis RW, Gethin DT, Yang XS, Rowe RC. A combined finite-discrete element method for simulating pharmaceutical powder tableting. Int J Num Meth Eng 2005 62 853-69. 

So far, some researchers have analyzed particle fluidization behaviors in a RFB, however, they have not well studied yet, since particle fluidization behaviors are very complicated. In this study, fundamental particle fluidization behaviors of Geldart s group B particle in a RFB were numerically analyzed by using a Discrete Element Method (DEM)- Computational Fluid Dynamics (CFD) coupling model [3]. First of all, visualization of particle fluidization behaviors in a RFB was conducted. Relationship between bed pressure drop and gas velocity was also investigated by the numerical simulation. In addition, fluctuations of bed pressure drop and particle mixing behaviors of radial direction were numerically analyzed. 

P.W. Cleary, Predicting charge motion, power draw, segregation and wear in ball mills using discrete element methods, Miner. Eng. 11 (1998) 1061-1080. 

Three types of theoretical approaches can be used for modeling the gas-particles flows in the pneumatic dryers, namely Two-Fluid Theory [1], Eulerian-Granular [2] and the Discrete Element Method [3]. Traditionally the Two-Fluid Theory was used to model dilute phase flow. In this theory, the solid phase is being considering as a pseudo-fluid. It is assumed that both phases are occupying every point of the computational domain with its own volume fraction. Thus, macroscopic balance equations of mass, momentum and energy for both the gas and the solid... 

Based on the pilot scale measurements mathematical modeling was started in order to describe the processes. Discrete element method (DEM) was used to model the mixing. This was originated from a simple mechanical model to formulate... 

Measurements were carried out in order to correct the existing discrete element methods that describe mixing effect of granules in a bulk. Different densities and friction coefficients of particles were studied to find correlations between the parameters and the mixing characteristics. There was found no effect of these parameters on mixing. Therefore, the DEM modeling work in this case has to be reevaluated. 

The mechanical response of systems of distinct particles is often adequately described by Newton s laws, which constitute the bases of classical mechanics (36) (see sect. The Discrete Element Method ). However, additional concepts are needed for deformable matter, such as stress and strain, which will be described here (37). We will focus on solid materials, but remark that the same principles are also valid for fluids (in which case the field is usually referred to as computational fluid dynamics). 

Munjiza A. The Combined Finite-Discrete Element Method. Chichester Wiley, 2004. 

Munjiza A, Owen DRJ, Bicanic N. A combined finite-discrete element method in transient dynamics of fracturing solids. Eng Comput 1995 12 145-174. 

DEM AND DYNAMIC SIMILARITY FOR PROCESS SIMULATION 3.1 Discrete element method (DEM)... 

The discrete element method regards each particle as an individual element, and where the motion of each particle is calculated according to the Newton s second law. At time t, the total response forces SF) and moments SM,- of each element to its surroundings produce linear (a) and angular (w) accelerations ... 

Several of the problems can be investigated by the Discrete Element Method, as different kinds of interactions can be prescribed (Fig. 9). For example the interactions could be spring or damper elements, which leads to a specific force network. 

Fig. 9 Material representation as point masses and interactions in the framework of the Discrete Element Method. Reprinted from Walhnersperger et al. (2007). Reproduced with kind permission of Wiley-VCH Verlag GmbH Co. KGaA.

Bicanic B (2004) Discrete element methods. In Stein E, de Borst R, Hughes TJR (eds) Encyclopedia of Computational Mechanics Fundamentals. Wiley, New York, pp 311-337 Bowen RM (1980) Incompressible porous media models by use of the theory of mixtures. Int JEngg Sci 18(9) 1129-1148... 

Numerically, these processes can be modeled by different techniques, such as finite-difference methods (FDM), finite-element methods (FEM). and discrete-element methods (DEM), as well as discrete fracture network (DFN) methods. In addition, many of the coupled processes are nonlinear, and the... 

Hybrid model of Discrete Fracture Network (DFN) and Discrete Element Method (DEM) for coupled stress-flow analysis of rock slope stability (Wang, 2000) ... 

Wang H. 2000. Hybrid model of discrete fracture network and discrete element method for rock slope stability analysis. J. of Hydrogeology Engineering Geology, Vol. 2, pp. 30-34. 

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