Near-wall effects in rarefied gas micro-flows: Some modern hydrodynamic approaches

Lynne O'Hare, Duncan A. Lockerby, Jason Reese, David Emerson

Research output: Contribution to journalArticle

36 Citations (Scopus)

Abstract

Methods for simulating the critical near-wall region in hydrodynamic models of gas micro-flows are discussed. Two important non-equilibrium flow features - velocity slip at solid walls, and the Knudsen layer (which extends one or two molecular mean free paths into the gas from a surface) - are investigated using different modelling approaches. In addition to a discussion of Maxwell's slip boundary condition, a newly implemented 'wall-function' model that has been developed to improve hydrodynamic simulations of the Knudsen layer is described. Phenomenological methods are compared to physical modelling and it is shown that, while both simulation types have merit, and both can quantitatively improve results in most cases, there are drawbacks associated with each approach. Phenomenological techniques, for example, may not be sufficiently general, whilst issues with applicability and stability are known to exist in some physical models. It is concluded that, at present, neither approach is unambiguously preferable to the other, and that both physical and phenomenological modelling should be the subject of future work.
LanguageEnglish
Pages37-43
Number of pages7
JournalInternational Journal of Heat and Fluid Flow
Volume28
Issue number1
DOIs
Publication statusPublished - Feb 2007

Fingerprint

rarefied gases
Hydrodynamics
Gases
hydrodynamics
slip
nonequilibrium flow
Wall function
gases
mean free path
simulation
Boundary conditions
boundary conditions

Keywords

  • microfluidics
  • rarefied gas dynamics
  • velocity slip
  • knudsen layer
  • wall-function
  • gas microsystems

Cite this

O'Hare, Lynne ; Lockerby, Duncan A. ; Reese, Jason ; Emerson, David. / Near-wall effects in rarefied gas micro-flows : Some modern hydrodynamic approaches. In: International Journal of Heat and Fluid Flow. 2007 ; Vol. 28, No. 1. pp. 37-43.
@article{5c2cf0fd78d74926a270ebf73b1c100e,
title = "Near-wall effects in rarefied gas micro-flows: Some modern hydrodynamic approaches",
abstract = "Methods for simulating the critical near-wall region in hydrodynamic models of gas micro-flows are discussed. Two important non-equilibrium flow features - velocity slip at solid walls, and the Knudsen layer (which extends one or two molecular mean free paths into the gas from a surface) - are investigated using different modelling approaches. In addition to a discussion of Maxwell's slip boundary condition, a newly implemented 'wall-function' model that has been developed to improve hydrodynamic simulations of the Knudsen layer is described. Phenomenological methods are compared to physical modelling and it is shown that, while both simulation types have merit, and both can quantitatively improve results in most cases, there are drawbacks associated with each approach. Phenomenological techniques, for example, may not be sufficiently general, whilst issues with applicability and stability are known to exist in some physical models. It is concluded that, at present, neither approach is unambiguously preferable to the other, and that both physical and phenomenological modelling should be the subject of future work.",
keywords = "microfluidics, rarefied gas dynamics, velocity slip, knudsen layer, wall-function, gas microsystems",
author = "Lynne O'Hare and Lockerby, {Duncan A.} and Jason Reese and David Emerson",
year = "2007",
month = "2",
doi = "10.1016/j.ijheatfluidflow.2006.04.012",
language = "English",
volume = "28",
pages = "37--43",
journal = "International Journal of Heat and Fluid Flow",
issn = "0142-727X",
number = "1",

}

Near-wall effects in rarefied gas micro-flows : Some modern hydrodynamic approaches. / O'Hare, Lynne; Lockerby, Duncan A. ; Reese, Jason; Emerson, David.

In: International Journal of Heat and Fluid Flow, Vol. 28, No. 1, 02.2007, p. 37-43.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Near-wall effects in rarefied gas micro-flows

T2 - International Journal of Heat and Fluid Flow

AU - O'Hare, Lynne

AU - Lockerby, Duncan A.

AU - Reese, Jason

AU - Emerson, David

PY - 2007/2

Y1 - 2007/2

N2 - Methods for simulating the critical near-wall region in hydrodynamic models of gas micro-flows are discussed. Two important non-equilibrium flow features - velocity slip at solid walls, and the Knudsen layer (which extends one or two molecular mean free paths into the gas from a surface) - are investigated using different modelling approaches. In addition to a discussion of Maxwell's slip boundary condition, a newly implemented 'wall-function' model that has been developed to improve hydrodynamic simulations of the Knudsen layer is described. Phenomenological methods are compared to physical modelling and it is shown that, while both simulation types have merit, and both can quantitatively improve results in most cases, there are drawbacks associated with each approach. Phenomenological techniques, for example, may not be sufficiently general, whilst issues with applicability and stability are known to exist in some physical models. It is concluded that, at present, neither approach is unambiguously preferable to the other, and that both physical and phenomenological modelling should be the subject of future work.

AB - Methods for simulating the critical near-wall region in hydrodynamic models of gas micro-flows are discussed. Two important non-equilibrium flow features - velocity slip at solid walls, and the Knudsen layer (which extends one or two molecular mean free paths into the gas from a surface) - are investigated using different modelling approaches. In addition to a discussion of Maxwell's slip boundary condition, a newly implemented 'wall-function' model that has been developed to improve hydrodynamic simulations of the Knudsen layer is described. Phenomenological methods are compared to physical modelling and it is shown that, while both simulation types have merit, and both can quantitatively improve results in most cases, there are drawbacks associated with each approach. Phenomenological techniques, for example, may not be sufficiently general, whilst issues with applicability and stability are known to exist in some physical models. It is concluded that, at present, neither approach is unambiguously preferable to the other, and that both physical and phenomenological modelling should be the subject of future work.

KW - microfluidics

KW - rarefied gas dynamics

KW - velocity slip

KW - knudsen layer

KW - wall-function

KW - gas microsystems

UR - http://www.sciencedirect.com/science/article/pii/S0142727X06001317

U2 - 10.1016/j.ijheatfluidflow.2006.04.012

DO - 10.1016/j.ijheatfluidflow.2006.04.012

M3 - Article

VL - 28

SP - 37

EP - 43

JO - International Journal of Heat and Fluid Flow

JF - International Journal of Heat and Fluid Flow

SN - 0142-727X

IS - 1

ER -