Variation of molecular mean free path in confined geometries

Jianfei Xie, Livio Gibelli, Matthew K. Borg, Oliver Henrich, Duncan A. Lockerby, Jason M. Reese

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This paper aims to settle disputes in the literature about the spatial variation of the molecular mean free path (MFP) in confined geometries. The MFP of a gas is determined by using both molecular dynamics (MD) and the direct simulation Monte Carlo (DSMC) technique. In spatially-homogeneous cases, the numerical results exactly recover the kinetic theory predictions of a constant MFP. However, in microchannels, the MFP is found to vary near to the bounding walls and reduce at the surfaces to half of its bulk value as long as collisions between gas molecules and wall atoms are taken into account in the calculation of the MFP.

Original languageEnglish
Article number090009
Number of pages7
JournalAIP Conference Proceedings
Publication statusPublished - 5 Aug 2019
Event31st International Symposium on Rarefied Gas Dynamics, RGD 2018 - Glasgow, United Kingdom
Duration: 23 Jul 201827 Jul 2018


  • DSMC method
  • molecular mean free path (MFP)
  • molecular dynamics


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