A hybrid molecular-continuum method for unsteady compressible multiscale flows

Matthew K. Borg, Duncan A. Lockerby, Jason M. Reese

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

We present an internal-flow multiscale method ('unsteady-IMM') for compressible, time-varying/unsteady flow problems in nano-confined high-aspect-ratio geometries. The IMM is a hybrid molecular-continuum method that provides accurate flow predictions at macroscopic scales because local microscopic corrections to the continuum-fluid formulation are generated by spatially and temporally distributed molecular simulations. Exploiting separation in both time and length scales enables orders of magnitude computational savings, far greater than seen in other hybrid methods. We apply the unsteady-IMM to a converging-diverging channel flow problem with various time- and length-scale separations. Comparisons are made with a full molecular simulation wherever possible; the level of accuracy of the hybrid solution is excellent in most cases. We demonstrate that the sensitivity of the accuracy of a solution to the macro-micro time-stepping, as well as the computational speed-up over a full molecular simulation, is dependent on the degree of scale separation that exists in a problem. For the largest channel lengths considered in this paper, a speed-up of six orders of magnitude has been obtained, compared with a notional full molecular simulation.

LanguageEnglish
Pages388-414
Number of pages27
JournalJournal of Fluid Mechanics
Volume768
Early online date10 Mar 2015
DOIs
Publication statusPublished - Apr 2015

Fingerprint

Compressible flow
continuums
simulation
Channel flow
Unsteady flow
internal flow
Macros
Aspect ratio
unsteady flow
channel flow
high aspect ratio
Fluids
Geometry
formulations
fluids
sensitivity
geometry
predictions

Keywords

  • computational methods
  • micro-/nano-fluid dynamics
  • molecular dynamics

Cite this

Borg, Matthew K. ; Lockerby, Duncan A. ; Reese, Jason M. / A hybrid molecular-continuum method for unsteady compressible multiscale flows. In: Journal of Fluid Mechanics. 2015 ; Vol. 768. pp. 388-414.
@article{342960392c7d432bbdd640d00f2d753f,
title = "A hybrid molecular-continuum method for unsteady compressible multiscale flows",
abstract = "We present an internal-flow multiscale method ('unsteady-IMM') for compressible, time-varying/unsteady flow problems in nano-confined high-aspect-ratio geometries. The IMM is a hybrid molecular-continuum method that provides accurate flow predictions at macroscopic scales because local microscopic corrections to the continuum-fluid formulation are generated by spatially and temporally distributed molecular simulations. Exploiting separation in both time and length scales enables orders of magnitude computational savings, far greater than seen in other hybrid methods. We apply the unsteady-IMM to a converging-diverging channel flow problem with various time- and length-scale separations. Comparisons are made with a full molecular simulation wherever possible; the level of accuracy of the hybrid solution is excellent in most cases. We demonstrate that the sensitivity of the accuracy of a solution to the macro-micro time-stepping, as well as the computational speed-up over a full molecular simulation, is dependent on the degree of scale separation that exists in a problem. For the largest channel lengths considered in this paper, a speed-up of six orders of magnitude has been obtained, compared with a notional full molecular simulation.",
keywords = "computational methods, micro-/nano-fluid dynamics, molecular dynamics",
author = "Borg, {Matthew K.} and Lockerby, {Duncan A.} and Reese, {Jason M.}",
year = "2015",
month = "4",
doi = "10.1017/jfm.2015.83",
language = "English",
volume = "768",
pages = "388--414",
journal = "Journal of Fluid Mechanics",
issn = "0022-1120",
publisher = "Cambridge University Press",

}

A hybrid molecular-continuum method for unsteady compressible multiscale flows. / Borg, Matthew K.; Lockerby, Duncan A.; Reese, Jason M.

In: Journal of Fluid Mechanics, Vol. 768, 04.2015, p. 388-414.

Research output: Contribution to journalArticle

TY - JOUR

T1 - A hybrid molecular-continuum method for unsteady compressible multiscale flows

AU - Borg, Matthew K.

AU - Lockerby, Duncan A.

AU - Reese, Jason M.

PY - 2015/4

Y1 - 2015/4

N2 - We present an internal-flow multiscale method ('unsteady-IMM') for compressible, time-varying/unsteady flow problems in nano-confined high-aspect-ratio geometries. The IMM is a hybrid molecular-continuum method that provides accurate flow predictions at macroscopic scales because local microscopic corrections to the continuum-fluid formulation are generated by spatially and temporally distributed molecular simulations. Exploiting separation in both time and length scales enables orders of magnitude computational savings, far greater than seen in other hybrid methods. We apply the unsteady-IMM to a converging-diverging channel flow problem with various time- and length-scale separations. Comparisons are made with a full molecular simulation wherever possible; the level of accuracy of the hybrid solution is excellent in most cases. We demonstrate that the sensitivity of the accuracy of a solution to the macro-micro time-stepping, as well as the computational speed-up over a full molecular simulation, is dependent on the degree of scale separation that exists in a problem. For the largest channel lengths considered in this paper, a speed-up of six orders of magnitude has been obtained, compared with a notional full molecular simulation.

AB - We present an internal-flow multiscale method ('unsteady-IMM') for compressible, time-varying/unsteady flow problems in nano-confined high-aspect-ratio geometries. The IMM is a hybrid molecular-continuum method that provides accurate flow predictions at macroscopic scales because local microscopic corrections to the continuum-fluid formulation are generated by spatially and temporally distributed molecular simulations. Exploiting separation in both time and length scales enables orders of magnitude computational savings, far greater than seen in other hybrid methods. We apply the unsteady-IMM to a converging-diverging channel flow problem with various time- and length-scale separations. Comparisons are made with a full molecular simulation wherever possible; the level of accuracy of the hybrid solution is excellent in most cases. We demonstrate that the sensitivity of the accuracy of a solution to the macro-micro time-stepping, as well as the computational speed-up over a full molecular simulation, is dependent on the degree of scale separation that exists in a problem. For the largest channel lengths considered in this paper, a speed-up of six orders of magnitude has been obtained, compared with a notional full molecular simulation.

KW - computational methods

KW - micro-/nano-fluid dynamics

KW - molecular dynamics

UR - http://www.scopus.com/inward/record.url?scp=84924709610&partnerID=8YFLogxK

U2 - 10.1017/jfm.2015.83

DO - 10.1017/jfm.2015.83

M3 - Article

VL - 768

SP - 388

EP - 414

JO - Journal of Fluid Mechanics

T2 - Journal of Fluid Mechanics

JF - Journal of Fluid Mechanics

SN - 0022-1120

ER -