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

Binder jet 3D printing—Process parameters, materials, properties, modeling, and challenges

http://www.mss.cbi.fau.de/content/uploads/parteli_particle_based_2015.pdf

Particle-based simulation of powder application in additive manufacturing

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

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

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

A parallelized resolved method for the simulation of the dynamics of immersed bodies within fluids is presented. The algorithm uses a FDM (fictitious domain method) and combines the Lagrangian DEM (discrete element method) for tracking the bodies with a CFD (computational fluid dynamics) method for calculating the dynamics of the fluid phase. First the CFD-calculation is carried out, disregarding the solid bodies. Afterwards, the velocity information from the bodies is included and the force, the fluid imposes onto the bodies, is computed. The last step consists of a correction-operation which ensures the fulfillment of the conservation equation. Dynamic local mesh refinement is used for minimizing the number of fluid cells. The CFD-DEM coupling is realized within the Open Source framework CFDEMcoupling (www.cfdem.com), where the DEM software LIGGGHTS (www.liggghts.com) is linked against an OpenFOAM®-based CFD solver. While both LIGGGHTS and the CFD solver were already parallelized, only a recent improvement of the algorithm permits the fully parallel computation of resolved problems. This parallelization permits the treatment of large-scale problems. The enclosed validation and application examples show the dynamics of the flow around settling and rotating spheres as well as an investigation of the settling of spheres regarding the Boycott effect.

/pdf/parallel-open-source-cfd-dem-for-resolved-particle-fluid-xwq1zzl25t.pdf

Parallel Open Source CFD-DEM for Resolved Particle-Fluid Interaction

Discrete Element Method (DEM) and DEM coupled to Computational Fluid Dynamics (CFD-DEM) are powerful techniques for optimization and design of particle processes. Macroscopic granular particles or flow involving fluids and granular particles are everywhere - in industry, environment and everyday lives: sugar, sand, ores, tablets, chemicals, biomass, detergents, plastics, crops, fruits need to be harvested, produced, processed, transported and stored. We highlight our vision of providing cutting edge simulation technology to an open public via the open source CFD-DEM software CFDEM®coupling (cf., Goniva et al. (2012)) and the open source DEM software LIGGGHTS® (cf., Kloss et al. (2012)). While open source guarantees transparency and security of investment it does not automatically enable everyone to easily apply the software. Often the installation of the required operating system or third-party software are hindering potential users from using open source software. By developing the commercial GUI CFDEM®workbench we provide an easy access route to the complex field of DEM and CFD-DEM modelling, which is fully compatible to its open source advantages. It combines the strength of the open source simulation software with the comfort of a guidance through the installation and setup process. We give an introduction to the software tool and highlight possible applications in fields such as steel industry, chemical industry, pharmaceutical industry, consumer goods industry, agricultural machinery production, food production, powder metallurgy and plastics production.

Alice Hager

Papers

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

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

Parallel Open Source CFD-DEM for Resolved Particle-Fluid Interaction

Combining Open Source and Easy Access in the field of DEM and coupled CFD-DEM: LIGGGHTS®, CFDEM®coupling and CFDEM®workbench

Unresolved CFD‐DEM in environmental engineering: submarine slope stability and other applications