Knudsen layer

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The Knudsen layer, also known as evaporation layer, is the thin layer of vapor near a liquid or solid. It is named after Danish physicist Martin Knudsen (1871–1949).

Definition

This region, several mean free path lengths thick, is called the Knudsen layer.^[1]

Knudsen layer thickness

The knudsen layer thickness can be approximated by $l_{c}$ , given by^[2]

$l_{c}={\frac {kT_{s}}{\pi d^{2}p_{s}}}$ ,

where $k$ is Boltzmann's constant, $T_{s}$ is the temperature, $d$ is the molecular diameter and $p_{s}$ is the pressure.

Applications

One of the applications of Knudsen layer is in the coma of comets. It has been used specially in the coma chemistry model (ComChem model).^[3]

References

↑ Aoki, K. (2003). Journal of Statistical Physics 112 (3/4): 629–655. doi:10.1023/A:1023876025363.
↑ Gusarov, A. V.; Smurov, I. (2002). "Gas-dynamic boundary conditions of evaporation and condensation: Numerical analysis of the Knudsen layer". Physics of Fluids 14 (12): 4242. Bibcode:2002PhFl...14.4242G. doi:10.1063/1.1516211.
↑ Huebner, W. F. (1987). "First Polymer in Space Identified in Comet Halley". Science 237 (4815): 628–630. doi:10.1126/science.237.4815.628. PMID 17758563.

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