Improved Metaball Discrete Element Method with Robust Contact Algorithm for General-Shaped Particles with Rounded Features

Particle shape is a critical factor governing the macroscopic behavior of granular materials. While the Discrete Element Method (DEM) has proven to be a powerful tool for modeling these materials, the accurate representation of particles with realistic geometries remains a significant challenge. Numerous shape description techniques have been developed to address this, including sphere-clustering, polyhedral, spheropolyhedral, and superquadric approaches. However, these methods often introduce artificial surface roughness or are limited to highly regular geometries, particularly when modeling general-shaped particles with rounded features. The proposed method reformulates collision detection in the Metaball Discrete Element Method (MDEM) as a constrained optimization problem, ensuring stable and physically consistent contact handling. Validation results show excellent agreement with analytical solutions and significantly improved robustness over unconstrained MDEM approaches. Finally, the model is applied to analyze the effects of particle shape on compaction and segregation, demonstrating that the proposed MDEM effectively captures the influence of complex shapes on macroscopic behavior and offers strong potential for engineering and scientific applications.