Coupling Atomistic and Continuum Models for Multi-scale Simulations of Gas Flows

Abstract

Abstract. This paper describes two computational tools linking atomistic and continuum models of gaseous systems. The first one, a Unified Flow Solver (UFS), is based on a direct Boltzmann solver and kinetic CFD schemes. The UFS uses an adaptive mesh and algorithm refinement procedure for automatic decomposition of computational domain into kinetic and continuum parts. The UFS has been used for a variety of flow problems in a wide range of Knudsen and Mach numbers. The second tool is a Multi-Scale Computational Environment (MSCE) integrating CFD tools with Kinetic Monte Carlo (KMC) and Molecular Dynamics (MD). The MSCE was applied for analysis of catalytic growth of vertically aligned carbon nanotubes (CNT) in a C 2 H 2 /H 2 inductively coupled plasma. The MSCE is capable of predicting paths for delivering carbon onto catalyst/CNT interface, formation of single wall or multi-wall CNTs depending on the shape of catalyst, and transition from nucleation to the steady growth of CNTs.

Simulation of Multiphysics Multiscale Systems: Introduction to the ICCS’2007 Workshop

“…The first one is the development of sophisticated models for each physical process, characterized by its own specific scales and its own mechanisms, and integration of these models into one seamless simulation. Coupling or extension of atomistic and continuum models studied in [8][9][10][11][12][13][14] shows that sophisticated modeling is essential to accurately represent the physical world. Similarly, works in [15][16][17][18] demonstrate that biological or biomedical systems have intrinsically multiscale nature and require multiscale modeling.…”

“…The projects in [8][9][10] investigate computationally efficient yet physically meaningful ways of coupling discrete and continuum models across multiple scales. Another way of treating multiscale problems is to develop single-scale approximation models.…”

“…The continuum domain is described by Navier-Stokes equations solved using a finite volume formulation in compressible form to capture the shock, and the molecular domain is solved by the Direct Simulation Monte Carlo method. Work conducted in [9] leads to development and application of two computational tools linking atomistic and continuum models of gaseous systems: the first tool, a Unified Flow Solver for rarefied and continuum flows, is based on a direct Boltzmann solver and kinetic CFD schemes, and the second tool is a multiscale computational environment integrating CFD tools with Kinetic Monte Carlo and Molecular Dynamics tools. Paper [10] describes an application of the Unified Flow Solver (UFS) for complex gas flows with rarefied and continuum regions.…”

Multiscale simulations of primary atomization

“…Disparate scales are seen in situations like micro and nano-fluidics, particle-laden flows, combustion chambers, spray drying and atmospheric flows [1,2]. Numerical simulations of a physical process involving temporal and spatial scales separated by orders of magnitude require huge computational resources and time.…”