Definition
The Knudsen number is a dimensionless number defined as:
where
- = mean free path
- = representative physical length scale .
For an ideal gas, the mean free path may be readily calculated so that:
where
- is the Boltzmann constant (1.3806504(24) × 10−23 J/K in SI units),
- is the thermodynamic temperature,
- is the particle hard shell diameter,
- is the total pressure, .
For particle dynamics in the atmosphere, and assuming standard temperature and pressure, i.e. 25 °C and 1 atm, we have ≈ 8 × 10−8 m.
Read more about this topic: Knudsen Number
Famous quotes containing the word definition:
“I’m beginning to think that the proper definition of “Man” is “an animal that writes letters.””
—Lewis Carroll [Charles Lutwidge Dodgson] (1832–1898)
“Scientific method is the way to truth, but it affords, even in
principle, no unique definition of truth. Any so-called pragmatic
definition of truth is doomed to failure equally.”
—Willard Van Orman Quine (b. 1908)
“Beauty, like all other qualities presented to human experience, is relative; and the definition of it becomes unmeaning and useless in proportion to its abstractness. To define beauty not in the most abstract, but in the most concrete terms possible, not to find a universal formula for it, but the formula which expresses most adequately this or that special manifestation of it, is the aim of the true student of aesthetics.”
—Walter Pater (1839–1894)