Molecular free path distribution in rarefied gases

Dongari, Nishanth and Zhang, Yonghao and Reese, Jason (2011) Molecular free path distribution in rarefied gases. Journal of Physics D: Applied Physics, 44 (12). Article 125502. ISSN 1361-6463 (https://doi.org/10.1088/0022-3727/44/12/125502)

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Abstract

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 Lévy-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.