The HECToR Service is now closed and has been superceded by ARCHER.

Scalable coupling of Molecular Dynamics and Direct Numerical Simulation of multi-scale flows Part 1

This project concerns two distinct computer codes on HECToR and their combined abilities to solve fluid flow problems across a wide range of physical scales. The first algorithm is a continuum-level, Direct Numerical Simulation (DNS) technique, which evolves the large-scale, macroscopic features in the flow by solving the non-linear Navier-Stokes equations (Transflow). The second algorithm is a Molecular Dynamics (MD) description of the atomic-level behaviour near flow boundaries (StreamMD). The flow boundaries can be near solid surfaces, or embedded near a two-fluid interface. The mathematical framework for fully coupling the continuum and molecular codes has been developed, and tested for simple canonical flows for a while.

The main objective of this project is to extend this interface for massively parallel, and highly-scalable simulations on HECToR which will be achieved by:

  • Developing a Continuum-to-Molecular Coupling and Embedding (CMCe) module. The CMCe module will be both a multi-physics (solid and fluid mechanics) and a hierarchical coupler (molecular to continuum). Multiple MPI communicators will be used to separate the message passing within Transflow and StreamMD.
  • Developing a DNS and MD interface Protocol. The key principle of the interface protocol is that the coupling process will be all performed within the CMCe module. The methods used should be transferrable to other CFD and MD applications as in principle this should allow any CFD and any MD to be coupled by a transfer of their domain halos.

The achievements of the project are summarised below:

  • The coupler includes a communications infrastructure (for internal data management) and interface module (for data access between applications).
  • For a Lennard-Jones system of 3,317,760 molecules, good scalability of the coupled CFD and MD application has been demonstrated on HECToR Phase 3 for up to 800 cores.

Please see PDF or HTML for a report which summarises this project.