Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Fast parallel algorithms for short-range molecular dynamics

LAMMPS - a flexible simulation tool for particle-based materials modeling at the atomic, meso, and continuum scales

DEM/CFD-DEM Modelling of Non-spherical Particulate Systems: Theoretical Developments and Applications

Handbook of Industrial Mixing: Science and Practice

We present a multi–purpose CFD–DEM framework to simulate coupled fluid–granular systems. The motion of the particles is resolved by means of the Discrete Element Method (DEM), and the Computational Fluid Dynamics (CFD) method is used to calculate the interstitial fluid flow. We first give a short overview over the DEM and CFD–DEM codes and implementations, followed by elaborating on the numerical schemes and implementation of the CFD–DEM coupling approach, which comprises two fundamentally different approaches, the unresolved CFD–DEM and the resolved CFD–DEM using an Immersed Boundary (IB) method. Both the DEM and the CFD–DEM approach are successfully tested against analytics as well as experimental data.

Models, algorithms and validation for opensource DEM and CFD-DEM

Development of an unresolved CFD-DEM model for the flow of viscous suspensions and its application to solid-liquid mixing

LIGGGHTS – Open Source Discrete Element Simulations of Granular Materials Based on Lammps

In the following paper the authors present a fully parallelized Open Source method for calculating the interaction of immersed bodies and surrounding fluid. Acombination of computational fluid dynamics (CFD) and a discrete element method (DEM) accounts for the physics of both the fluid and the particles. The objects considered are relatively big compared to the cells of the fluid mesh, i.e. they cover several cells each. Thus this fictitious domain method (FDM) is called resolved. The implementation is realized within the Open Source framework CFDEMcoupling (www.cfdem.com), which provides an interface between OpenFOAM® based CFD-solvers and the DEM software LIGGGHTS (www.liggghts.com). While both LIGGGHTS and OpenFOAM® were already parallelized, only a recent improvement of the algorithm permits the fully parallel computation of resolved problems. Alongside with a detailed description of the method, its implementation and recent improvements, a number of application and validation examples is presented in...

https://journals.sagepub.com/doi/pdf/10.1260/1757-482X.6.1.13

Christoph Goniva

Papers

Models, algorithms and validation for opensource DEM and CFD-DEM

Development of an unresolved CFD-DEM model for the flow of viscous suspensions and its application to solid-liquid mixing

LIGGGHTS – Open Source Discrete Element Simulations of Granular Materials Based on Lammps

Parallel Resolved Open Source CFD-DEM: Method, Validation and Application

Coarse Graining for Large-scale DEM Simulations of Particle Flow – An Investigation on Contact and Cohesion Models