A hybrid atomistic-continuum model for fluid flow using LAMMPS and OpenFOAM

A fully parallelized hybrid atomistic-continuum (HAC) model, built from the open source codes LAMMPS and OpenFOAM, is developed to resolve nanoscale features of fluid flow. The domain is decomposed into an atomistic domain, where individual atomic interactions are computed, and a continuum domain, where the Navier-Stokes equations are solved. The two domains are coupled through an overlap region in which the solutions in both domains are consistent. The accuracy of the HAC model is demonstrated through the simulation of sudden start Couette flow. The hybrid model is shown to reduce computation time by a factor of five for a 78 nm channel as compared to a fully-atomistic simulation; this speedup is expected to become even greater for larger systems. Program Summary Program title: HacFoam Catalogue identifier: AEPC_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEPC_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 82519 No. of bytes in distributed program, including test data, etc.: 367728 Distribution format: tar.gz Programming language: C++. Computer: All capable of running Linux. Operating system: Linux. Has the code been vectorized or parallelized?: Parallelized with MPI Classification: 7.7. External routines: MPI, LAMMPS (http://lammps.sandia.gov/), OpenFOAM (http://www.openfoam.org) Nature of problem: Continuum methods are often incapable of resolving features and flow patterns in confined nanoscale liquid flows. Macroscopic simulations are far beyond the reach of atomistic simulations. Combining the atomistic resolution of molecular dynamics with the reduced computational expense of traditional continuum numerical techniques for fluid flow would allow larger scale problems to be studied. Solution method: The domain is decomposed into an atomistic domain and a continuum domain. Molecular dynamics (LAMMPS) is used in the atomistic domain while the Navier-Stokes equations are solved (OpenFOAM) in the continuum domain. The two domains are coupled through an overlap region where the two solutions communicate. LAMMPS and OpenFOAM are combined into a single executable, in the form of an OpenFOAM solver named HacFoam. Running time: HacFoam can vary from minutes to days to weeks depending on the size of the system, length of time simulated and number of processors used. (C) 2013 Elsevier B.V. All rights reserved.