Hybrid atomistic-continuum formulations for gaseous flows

Hybrid atomistic-continuum formulations allow the simulation of complex hydrodynamic phenomena at the nano and micro scales without the prohibitive cost of a fully atomistic approach. This is achieved through a domain decomposition strategy whereby the atomistic model is limited to regions of the flow field where required and the continuum model is implemented side-by-side in the remainder of the domain within a single computational framework. The current work is focused on arguably the most critical elements of any hybrid formulation: the atomistic-continuum coupling method and the imposition of continuum boundary conditions on the atomistic subdomain. The relative merits of different approaches for both are delineated and demonstrated using sample test problems. For the case of incompressible steady gaseous flows a hybrid formulation is developed using a finite element method for the continuum subdomain and the direct simulation Monte Carlo (DSMC) method for the atomistic subdomain. The Schwarz alternating method is used to couple both subdomains using an overlap region across which the successive exchange of Dirichlet boundary conditions yields a steady state solution. This approach has the advantages of decoupling both length scales and time scales of the atomistic and continuum solvers leading to superior performance over conventional explicit schemes. Continuum boundary conditions are imposed on the atomistic subdomain using the Chapman-Enskog distribution function in conjunction with particle reservoirs. A driven cavity test problem shows convergence in 0(10) Schwarz iterations for flow Reynolds numbers 0(1).

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2003

Author dc:creator

• Wijesinghe, Hettithanthrige Sanith, 1974-

Advisor dc:contributor.advisor

• Nicholas G. Hadjiconstantinou.

• Aeronautics and Astronautics.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/17021

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/17021