PeliGRIFF, a parallel DEM-DLM/FD direct numerical simulation tool for 3D particulate flows

The problem of particulate flows at moderate to high concentration and finite Reynolds number is addressed by parallel direct numerical simulation. The present contribution is an extension of the work published in Computers & Fluids 38:1608 (2009), where systems of moderate size in a 2D geometry were examined. At the numerical level, the suggested method is inspired by the framework established by Glowinski et al. (Int J Multiph Flow 25:755, 1999) in the sense that their Distributed Lagrange Multiplier/Fictitious Domain (DLM/FD) formulation and their operator-splitting idea are employed. In contrast, particle collisions are handled by an efficient Discrete Element Method (DEM) granular solver, which allows one to consider both smoothly (sphere) and non-smoothly (angular polyhedron) shaped particles. From a computational viewpoint, a basic though efficient strategy has been developed to implement the DLM/FD method in a domain decomposition/distributed fashion. To achieve this goal, the serial code, GRIFF (GRains In Fluid Flow; see Comput Fluids 38:1608-1628, 2009) is upgraded to fully MPI capabilities. The new code, PeliGRIFF (Parallel Efficient Library for GRains in Fluid Flow) is developed under the framework of the fully MPI open-source platform PELICANS. The parallel computing capabilities of PeliGRIFF offer new perspectives in the study of particulate flows and indeed increase the number of particles usually simulated in the literature. Solutions to address new issues raised by the parallelization of the DLM/FD method and assess the scalable properties of the code are proposed. Results on the 2D/3D sedimentation of a significant collection of isometric polygonal/polyhedral particles in a Newtonian fluid with collisions are presented as a validation test and an illustration of the class of particulate flows PeliGRIFF is able to investigate.