Distinct Element Method (DEM) Simulation

Distinct Element Method (DEM) is a numerical modelling method originally developed by Cundall (1971) for rock mechanics applications. Later, Cundall and Strack (1979) developed TRUBAL, a computer code for granular media applications. In the last 10 years a number of commercial DEM software (such as PFC3D and EDEM supplied by Itasca and DEM solutions, respectively) have become available. Essentially, in DEM Newton's second law of motion are solved for different elements (usually discs or spherical particles). The contact forces on particles are calculated from the collisions or contact interactions with other elements using a specified contact law. This contact law is usually either linear (based on a linear springs) or Hertzian (1896). The equations are all solved in small time-steps (normally based on Rayleigh wave propagation) and the values of position, velocity, acceleration and contact forces are updated. The simulation space is split into grids to locate particles and their contacts more rapidly. DEM is now generally well established and has been used extensively (Cleary and Sawley, 2002). It is a very useful tool as all microscopic interactions are recorded. Difficult dynamic systems can be simulated in contrast to continuum mechanics approaches. Although DEM has some limitation as only a relatively small number of particles can be simulated (up to a million as of 2008) and it is usually restricted to spherical shaped particles, polygons, or overlapping spherical particles. Nevertheless, recent work has shown that complex shapes are being introduced ( Tijskens and Rioual, 2008).

Our research group has three DEM codes. The current academic version of the code in our research group, TRUBAL is based on the version developed by Thornton and co-workers. In addition to this software our group has commercial licenses for both EDEM and PFC3D DEM softwares.

TRUBAL

DEM has been implemented for the simulation of various engineering applications such as agglomerate deformation and breakage, bulk compression behaviour of particles, shear deformation of particles, flowability, granulation of powders, mixing, segragation, electrostatic charging and dispersion.