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

¹ School of Civil Engineering, The University of Sydney, Sydney, Australia
² School of Resources and Civil Engineering, Northeastern University, Shenyang, China

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Published online: 1 December 2025

Abstract

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 (D_f) and relative roughness (R_r). 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 R_r than by D_f, highlighting the dominant role of surface roughness in the inertial regime.