A DEM Simulation on Irregular-shaped Intruders Moving in Granular Media

An intruder moving in a granular medium is a common phenomenon in nature and plays a crucial role in a wide range of industrial processes. Although regular-shaped intruders, such as spheres, ellipsoids, and cylinders, have been extensively studied, the behaviour of irregular-shaped intruders remains poorly understood. In this study, we employ the Discrete Element Method (DEM) to investigate the drag force acting on an irregular intruder moving in a granular bed consisting of spherical particles. The intruder’s morphological irregularity is constructed using spherical harmonics and is controlled by two shape parameters: fractal dimension (Df) and relative roughness (Rr). Our results indicate that the influence of shape on drag forces is limited in the quasi-static regime where the intruder moves at relatively low velocities. At higher velocities, however, the drag force exhibits a quadratic relationship with velocity for irregular-shaped intruders, similar to that observed for spherical ones. Notably, the prefactor in this relationship is more strongly influenced by Rr than by Df, highlighting the dominant role of surface roughness in the inertial regime.