A Hybrid Particle-Continuum Framework

Abstract

A new hybrid particle-continuum numerical code is currently being developed as an engineering tool for accurate and fast computational modelling of nanoflows. Molecular Dynamics (MD) and Computational Fluid Dynamics (CFD) are the components/solvers used within the particle and continuum zones respectively. In this paper the development of a two-component hybrid framework, based on domain-decomposition, is described. The main objective of the framework is to facilitate hybrid MD-CFD simulations within complex geometries, using a mesh of structured/unstructured arbitrary polyhedral cells, identical to that used in engineering CFD. This requires complex three-dimensional (3D) interfaces and overlap regions (comprising user-defined sub-regions) to be constructed between adjacent zones. The individual sub-regions serve as an appropriate means of exchanging information between components (i.e. coupling or boundary condition imposition), in 3D, during the hybrid simulation. The global domain is decomposed appropriately into MD and CFD sub-domains such that internal boundaries within the overlap regions become the external boundaries on the separate meshes, prior to commencing the hybrid simulations. The hybrid framework is implemented in OpenFOAM [1], an open source C++ CFD toolbox, using a general, case-independent approach and is parallelised. Two nanochannel test cases are investigated to show that the hybrid environment is flexible and well-suited for engineering design applications as well for the development of new hybrid codes and coupling models.