MaMiCo: Transient multi-instance molecular-continuum flow simulation on supercomputers

Abstract

We present extensions of the macro–micro-coupling tool MaMiCo, which was designed to couple continuum fluid dynamics solvers with discrete particle dynamics. To enable local extraction of smooth flow field quantities especially on rather short time scales, sampling over an ensemble of molecular dynamics simulations is introduced. We provide details on these extensions including the transient coupling algorithm, open boundary forcing, and multi-instance sampling. Furthermore, we validate the coupling in Couette flow using different particle simulation software packages and particle models, i.e. molecular dynamics and dissipative particle dynamics. Finally, we demonstrate the parallel scalability of the molecular-continuum simulations by using up to 65 536 compute cores of the supercomputer Shaheen II located at KAUST. New version program summaryProgram Title: MaMiCoProgram Files doi:http://dx.doi.org/10.17632/w7rgdrhb85.1Licensing provisions: BSD 3-clauseProgramming language: C, C++External routines/libraries: For compiling: SCons, MPI (optional)Subprograms used: ESPResSo, LAMMPS, ls1 mardyn, waLBerlaFor installation procedures of the MaMiCo interfaces, see the README files in the respective code directories located in coupling/interface/impl.Journal reference of previous version: P. Neumann, H. Flohr, R. Arora, P. Jarmatz, N. Tchipev, H.-J. Bungartz. MaMiCo: Software design for parallel molecular-continuum flow simulations, Computer Physics Communications 200: 324–335, 2016Does the new version supersede the previous version?: Yes. The functionality of the previous version is completely retained in the new version.Nature of problem: Coupled molecular-continuum simulation for multi-resolution fluid dynamics: parts of the domain are resolved by molecular dynamics or another particle-based solver whereas large parts are covered by a mesh-based CFD solver, e.g. a lattice Boltzmann automaton.Solution method: We couple existing MD and CFD solvers via MaMiCo (macro–micro coupling tool). Data exchange and coupling algorithmics are abstracted and incorporated in MaMiCo. Once an algorithm is set up in MaMiCo, it can be used and extended, even if other solvers are used (as soon as the respective interfaces are implemented/available).Reasons for the new version: We have incorporated a new algorithm to simulate transient molecular-continuum systems and to automatically sample data over multiple MD runs that can be executed simultaneously (on, e.g., a compute cluster). MaMiCo has further been extended by an interface to incorporate boundary forcing to account for open molecular dynamics boundaries. Besides support for coupling with various MD and CFD frameworks, the new version contains a test case that allows to run molecular-continuum Couette flow simulations out-of-the-box. No external tools or simulation codes are required anymore. However, the user is free to switch from the included MD simulation package to LAMMPS.For details on how to run the transient Couette problem, see the file README in the folder coupling/tests, Remark on MaMiCo V1.1.Summary of revisions: Open boundary forcing; Multi-instance MD sampling; support for transient molecular-continuum systemsRestrictions: Currently, only single-centered systems are supported.For access to the LAMMPS-based implementation of DPD boundary forcing, please contact Xin Bian, xin.bian@tum.de.Additional comments: Please see file license_mamico.txt for further details regarding distribution and advertising of this software.