Institute of Mechanics and Ocean Engineering

Description

DEMuM is a reserach toolbox for modeling and simulation of granular systems. The name DEMuM is a combination of the abbreviations DEM (Discrete Element Method) and MuM (Mechanik und Meerestechnik). The toolbox enables scientist and students an efficient simulation of granular systems as well as the quick implementation of new algorithms. Main part of the program is DEM-code implemented in Matlab. Following features are part of the program:

• Complex particle shapes (using Kardan-angles)
• Complex rigid bodies (by triangulated surface)
• Rigid body movement via: FEM coupling, rheonomic constraints
• Efficient time integration scheme using a time step controlled gear algorithm
• Efficient contact search (verlet-list + Grid Cell algorithm)
• Multiple contact laws (linear & non-linear)
• Dynamical placement and removal of particles
• Postprocessing: Calculation of FRF, DWT or complex power of the rigid bodies
• Animation of the system

DEM

The Discrete Element Method (DEM) is a discrete simulation method for granular materials. The DEM has been developed by Cundall and Strack [1] for the simulation of systems consisting of discs and  spheres. Its general concept can be used for any system of many unconstrained particles where the  system behavior is governed by the contacts between these particles [2]. While in general the particles can have an arbitrary shape, for efficiency purposes mostly spherical particles are used in the  simulations. Every particle is considered as an unconstrained moving body only influenced by applied forces. The dynamics are obtained by setting up Newton’s and Euler’s equation of motion for every particle [3].
Particle systems often contain a large number of particles (up to thousands or millions). During the time integration, all existing contacts need to be detected and resolved in every time step. Therefore, efficient detection algorithms and contact laws are needed. Also, the choice of an appropriate time integration scheme is crucial.
In DEM simulations, particle-particle and particle-wall continuous contacts occur. The contact partners are treated as rigid, thus only touching in a single point. In continuous contact modeling, the contact partners are allowed to overlap, and virtually connected by unilateral springs and dampers. Hereby, the corresponding contact forces occur which counteract the overlap.

Research

The program is used for the following reasearch topics:

• Particle dampers for passive vibration attenuation in flexible multibody systems (Partikeldämpfer zur passiven Schwingungsdämpfung in flexiblen Mehrkörpersystemen)