A method for representing boundaries in discrete element modelling—part II: Kinematics

The application of the DEM to engineering problems involving the dynamic behaviour of discontinuous media has necessitated the introduction of moving boundary surfaces. In this paper a method is presented for modelling three‐dimensional moving boundary surfaces within the discrete element framework. The surfaces of boundary objects are discretized into triangular planar surfaces using the finite wall method. Wall elements are grouped and each group is associated with a single discrete boundary object which may move independently. Movement comprises any combination of translation and rotation of wall element groups, subject to a given acceleration and velocity during a calculation cycle. The scheme is explicit due to rigidity of the wall elements which are stationary fixed in position and orientation over a time step. Any in‐plane velocity is handled as a contact point velocity within a calculation cycle. The kinematic conditions at each calculation cycle may be pre‐defined or returned from a separate calculation of rigid body motion of the boundary object. The method provides a means for coupling sphere‐based particle dynamics with rigid body dynamics and structural analysis of boundary components.