A GPU-accelerated simulator for the DEM analysis of granular systems composed of clump-shaped elements

This paper discusses the use of the discrete element method (DEM) to simulate the dynamics of granular systems made up of elements with nontrivial geometries. The DEM simulator is GPU accelerated and can handle elements whose shape is defined as the union with overlap of diverse sets of spheres with user-specified radii. The simulator can also handle complex materials since each sphere in an element can have its own Young’s modulus E , Poisson ratio ν , friction coefficient μ , and coefficient of restitution CoR. To demonstrate the simulator, this paper introduces a “digital simulant” (DS), a replica of the GRC-1 lunar simulant. The DS follows an element size distribution similar but not identical to that of GRC-1. The predictive attributes of the simulator are validated via several numerical experiments: repose angle, cone penetration, drawbar pull, and rover incline-climbing tests. Subsequently, a sensitivity analysis is carried out to gauge how the slope vs. slip curves change when the element shape, element size, and friction coefficient change. The paper concludes with a VIPER rover simulation that confirms a recently proposed granular scaling law. The simulation involves more than 11 million elements composed of more than 34 million spheres of different radii. The simulator works in the Chrono framework and can utilize two GPUs concurrently. The GPU code for the simulator and all numerical experiments discussed are open-source and available on GitHub for reproducibility studies and unfettered use and distribution. The DEM simulator introduced here: can handle complex particle geometry; can capture material breakage; can handle user-defined contact forces; allows for one DEM element to have different material properties in different regions of the element; is fast and runs on commodity hardware; can leverage two GPU cards simultaneously; it has a Python interface; and, it works in co-simulation mode with and augments Chrono, an established multi-body dynamics platform that supports the physics-based simulation of complex mechanical systems.