Knudsen number ( related to mean free path)


The Knudsen number (Kn) is a dimensionless number defined as the ratio of the molecular mean free path length to a representative physical length scale. This length scale could be, for example, the radius of the body in a fluid. (The mean free path is the average distance travelled by a moving particle (such as an atom, a molecule, a photon) between successive impacts (collisions), which modify its direction or energy or other particle properties.)

Related formulas


KnThe Knudsen number (dimensionless)
λThe molecular mean free path length (m)
LThe representative physical length scale (m)