Lethe-DEM: an open-source parallel discrete element solver with load balancing

Approximately 75% of the raw material and 50% of the products in the chemical industry are granular materials. The discrete element method (DEM) provides detailed insights of phenomena at particle scale, and it is therefore often used for modeling granular materials. However, because DEM tracks the motion and contact of individual particles separately, its computational cost increases nonlinearly O (n(p) log(n(p))) - O (n(2)) (depending on the algorithm) with the number of particles (n(p)). In this article, we introduce a new open-source parallel DEM software with load balancing: Lethe-DEM. Lethe-DEM, a module of Lethe, consists of solvers for two-dimensional and three-dimensional DEM simulations. Load balancing allows LetheDEM to significantly increase the parallel efficiency by approximate to 25-70% depending on the granular simulation. We explain the fundamental modules of Lethe-DEM, its software architecture, and the governing equations. Furthermore, we verify LetheDEM with several tests including analytical solutions and comparison with other software. Comparisons with experiments in a flat-bottomed silo, wedge-shaped silo, and rotating drum validate Lethe-DEM. We investigate the strong and weak scaling of Lethe-DEM with 1 <= n(c) <= 192 and 32 <= n(c) <= 320 processes, respectively, with and without load balancing. The strong-scaling analysis is performed on the wedge-shaped silo and rotating drum simulations, while for the weak-scaling analysis, we use a dam-break simulation. The best scalability of Lethe-DEM is obtained in the range of 5000 <= n(p)/n(c) <= 15,000. Finally, we demonstrate that large-scale simulations can be carried out with Lethe-DEM using the simulation of a three-dimensional cylindrical silo with n(p) = 4.3 x 10(6) on 320 cores.

Automated summary

This article introduces a new open-source parallel discrete element method (DEM) software, Lethe-DEM, with load balancing capability for simulating granular materials. Several tests have been conducted to validate the feasibility and scalability of the software.