Knudsen Number

Written by Jerry Ratzlaff on . Posted in Dimensionless Numbers

Knudsen number, abbreviated as Kn, a dimensionless number, is used in fluid dynamics to determine what type of analysis should be used to model an object moving through a fluid.  It is defined as the ratio of the molecular mean free path length to a representative physical length scale.  This calculation determines the Knudsen number, the length or the lambda value based on your inputs.


Knudsen number calculator



Knudsen Number formula

\(\large{ Kn = \frac{ \lambda }{ l } }\)   


 Units English Metric
\(\large{ Kn }\) = Knudsen number \(\large{dimensionless}\)
\(\large{ l }\) = length \(\large{in}\) \(\large{mm}\)
\(\large{ \lambda }\) (Greek symbol lambda) = mean free path \(\large{in}\) \(\large{mm}\)

Solve For:

\(\large{ l = \frac{ \lambda }{ Kn } }\)   
\(\large{ \lambda = Kn \; l  }\)   


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Tags: Fluid Equations Calculators