Molecular free path distribution in rarefied gases

Nishanth Dongari, Yonghao Zhang, Jason M. Reese

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We present the results of investigations into the distribution of molecular free paths in rarefied gases using molecular dynamics simulations. Our tests on a range of different gas densities and confinements (unbounded, single bounding wall and parallel bounding walls) indicate that the molecules perform Levy-type flights, irrespective of the presence of a bounding wall. The free paths most closely follow a power-law distribution. Simulations of gases confined by planar surfaces indicate that the local molecular mean free path varies sharply close to a solid surface. These results may yield new insight into diffusive transport in rarefied gases, in particular, the constitutive behaviour of gas flows in micro-and nanoscale devices.

Original languageEnglish
Article number125502
Number of pages6
JournalJournal of Physics D: Applied Physics
Issue number12
Publication statusPublished - 30 Mar 2011


  • mean free path
  • rarefied gas dynamics
  • non-equilibrium
  • kinetic theory
  • molecular dynamics
  • power law
  • mathematical model
  • diffusive transport
  • transition-continuum regime
  • Knudsen number

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