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Persistent URL
http://purl.org/net/epubs/work/34610
Record Status
Checked
Record Id
34610
Title
Challenges in modeling gas-phase flow in microchannels: from slip to transition
Contributors
RW Barber (CCLRC Daresbury Lab.)
,
DR Emerson (CCLRC Daresbury Lab.)
Abstract
It has long been recognized that the fluid mechanics of gas-phase microflows can differ significantly from the macroscopic world. Non-equilibrium effects such as rarefaction and gas-surface interactions need to be taken into account and it is well known that the no-slip boundary condition of the Navier-Stokes equations is no longer valid. Following ideas proposed by Maxwell, it is generally accepted that the Navier-Stokes equations can be extended into the slip-flow regime provided the Knudsen number is less than 0.1. Improvements in micro-fabrication techniques, however, are now enabling devices to be constructed with sub-micron feature sizes. At this scale, the flow will depart even further from equilibrium and will enter the transition regime. In recent years, there has been considerable success in the implementation of second-order slip-boundary conditions to extend the Navier-Stokes equations into the transition regime. Unfortunately, as yet, no consensus has been reached on the correct form of higher-order approach, with theoretical and experimental studies revealing large discrepancies in the magnitude of the second-order slip coefficient. It is believed that these discrepancies can be explained by the fact that continuum flow analyses neglect the Knudsen layer, which extends approximately one mean-free path from the channel wall. In addition, comparisons between kinetic and continuum slip-boundary formulations reveal another important source of error due to different definitions in the first-order slip coefficient. The paper explains how these discrepancies have arisen and describes future research directions that may help reconcile the different forms of higher-order approach.
Organisation
CCLRC
,
CSE
,
CSE-CEG
Keywords
Non-continuum
,
Non-equilibrium
,
Microfluidics
,
Rarefied
Funding Information
Related Research Object(s):
Licence Information:
Language
English (EN)
Type
Details
URI(s)
Local file(s)
Year
Paper In Conference Proceedings
In 3rd International Conference on Microchannels and Minichannels (ICMM05), Toronto, Canada, 13-15 Jun 2005, (2005).
2005
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