A-to-Z Guide to Thermodynamics,
Heat & Mass Transfer, and Fluids Engineering
English Русский 中文 Português Español Français Deutsch About Editors Contact us Access Begell House
View in Semantic Map View in A-Z Index

The Knudsen number K is usually defined for a gas as the ratio

(1)

where 1 is the mean free path and L is any macroscopic dimension of interest. The importance of this number is that, when K << 1, the gas behaves as a continuum fluid on the length scale L. The regime in which K << 1 is known as the hydrodynamic regime while that in which K >> 1 is known as the Knudsen regime. In the former, the gas obeys the Navier-Stokes equations of hydrodynamics while in the latter, rarefied gas dynamics apply.

REFERENCES

Truesdell, C. and Muncaster, R. G. (1980) Fundamentals of Maxwell's Kinetic Theory of a Simple Monatomic Gas. Academic Press. New York.

References

  1. Truesdell, C. and Muncaster, R. G. (1980) Fundamentals of Maxwell's Kinetic Theory of a Simple Monatomic Gas. Academic Press. New York.
Number of views: 37806 Article added: 2 February 2011 Article last modified: 11 February 2011 © Copyright 2010-2021 Back to top
A-Z Index Authors / Editors Semantic Map Visual Gallery Contribute Guest