Numerical Comparison of Contact Force Models in the Discrete Element Method

The discrete element method (DEM) is usually applied in analyzing the scientifical origin/evolution of the asteroids and the landing/sampling of the regolith. In order to manage the contact between the non-spherical granules, the Polygonal Contact Model (PCM) has been introduced into the DEM method. This paper applies four different contact force models in the newly-proposed DEM algorithm to analyze their difference and implication. The four contact force models include one linear model and three nonlinear models derived from the complete Mindlin–Deresiewicz equations. By considering the macroscopical results and calculation efficiency, the single-collision and multiple-collision cases are analyzed by comparing the four contact models. Specifically, the restitution coefficient, the angular velocity, the rebound angle, and the kinetic energy are applied as indicators for the single collision. The multiple-collision case is studied under the Brazil nut effect with ellipsoidal granules. Additionally, the softening feasibility is also discussed by decreasing the Young’s modulus of the material, mainly analyzing the outgoing results and the calculation efficiency.