View source for Knudsen number

The '''Knudsen number''' ('''Kn''') is a [[Dimensionless quantity|dimensionless number]] defined as the ratio of the molecular [[mean free path]] length to a representative physical length [[Scale (ratio)|scale]].

This length scale could be, for example, the [[radius]] of a [[body]] in a [[fluid]].

The number is named after Danish physicist [[Martin Knudsen]] (1871–1949).

== See also ==

* [[Dimensionless quantity]]
* [[Mean free path]]
* [[Physics]]
* [[Scale (ratio)]]

== External links ==

* [https://en.wikipedia.org/wiki/Knudsen_number Knudsen number] @ Wikipedia