Effective mean free path and viscosity of confined gases

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

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

The molecular mean free path (MFP) of gases in confined geometries is numerically evaluated by means of the direct simulation Monte Carlo method and molecular dynamics simulations. Our results show that if calculations take into account not only intermolecular interactions between gas molecules but also collisions between gas molecules and wall atoms, then a space-dependent MFP is obtained. The latter, in turn, permits one to define an effective viscosity of confined gases that also varies spatially. Both the gas MFP and viscosity variation in surface-confined systems have been questioned in the past. In this work, we demonstrate that this effective viscosity derived from our MFP calculations is consistent with those deduced from the linear-response relationship between the shear stress and strain rate using independent nonequilibrium Couette-style simulations as well as the equilibrium Green-Kubo predictions.
Original languageEnglish
Article number072002
Number of pages10
JournalPhysics of Fluids
Issue number7
Early online date16 Jul 2019
Publication statusE-pub ahead of print - 16 Jul 2019

Keywords / Materials (for Non-textual outputs)

  • kinetic theory
  • Microchannel
  • chemical elements
  • Computational Fluid Dynamics
  • molecular dynamics
  • Collision frequency
  • Laminar flow


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