We propose a technique to simulate granular materials that exploits the dual strengths of discrete and continuum treatments. Discrete element simulations provide unmatched levels of detail and generality, but prove excessively costly when applied to large scale systems. Continuum approaches are computationally tractable, but limited in applicability due to built-in modeling assumptions; e.g., models suitable for granular flows typically fail to capture clogging, bouncing and ballistic motion. In our hybrid approach, an oracle dynamically partitions the domain into continuum regions where safe, and discrete regions where necessary. The domains overlap along transition zones, where a Lagrangian dynamics mass-splitting coupling principle enforces agreement between the two simulation states. Enrichment and homogenization operations allow the partitions to evolve over time. This approach accurately and efficiently simulates scenarios that previously required an entirely discrete treatment.

Granular materials, Material point method, Contact dynamics, Constraints, Physical simulation

We thank Henrique Teles Maia for his help in producing the video, Gabriel Cirio for creating the funnel mesh, as well as Sachith Dunatunga, Chenfanfu Jiang, Andre Pradhana, and Yun Fei for insightful discussions. This work was supported in part by JSPS (Grant-in-Aid for Young Scientists (A) 17H04682), NSF (Grants CBET-17-06689, IIS-11-17257, IIS-12-17904, IIS-13-19483, IIS-14-09286, CMMI-11-29917, CMMI-13- 31499), IARPA (Grant 2014-14071600012), Adobe, and Autodesk.