DEM with attraction forces using reduced particle stiffness

In Discrete Element Method (DEM), the stiffness of particles is often reduced from the real material property to increase the time step and decrease the calculation cost. Although this approach is widely accepted for dry and relatively coarse particles where only contact force is dominant, it is recently reported that the powder behaviour changes drastically with reducing the particle stiffness when cohesion forces are exerted on the particles [1,2]. The present study generalises this problem to any type of attraction forces and provides a solution, which is named as the Reduced Particle Stiffness (RPS) scaling. The RPS scaling for both linear and non-linear contact models are developed based on the dimensionless equation of motion where additional attraction forces such as liquid bridge, cohesion and electrostatic forces are exerted on particles. It is proven that, using the RPS scaling, particles with reduced stiffness show similar sticking/rebound behaviour and the bulk velocity as those of the original (stiff) particles. (C) 2017 Elsevier B.V. All rights reserved.