Discrete Element Modeling:
"A discrete element algorithm is a numerical technique which solves engineering problems that are modeled as a large system of distinct interacting general shaped (deformable or rigid) bodies or particles that are subject to gross motion. Engineering problems that exhibit such large scale discontinuous behavior cannot be solved with a conventional continuum based procedure such as the Finite Element Method. The discrete element procedure is used to determine the dynamic contact topology of the bodies. It accounts for complex non-linear interaction phenomena between bodies and numerically solves the equations of motion. Since the DEM is a very computationally intensive procedure, many existing computer codes are limited to modeling either two-dimensional or small three-dimensional problems that employ simple body geometries. " ...http://egweb.mines.edu/dem/
