In fluid dynamics, the Knudsen equation is used to describe how gas flows through a tube in free molecular flow. When the mean free path of the molecules in the gas is larger than or equal to the diameter of the tube, the molecules will interact more often with the walls of the tube than with each other. For typical tube dimensions, this occurs only in high or ultrahigh vacuum.
The equation was developed by Martin Hans Christian Knudsen (1871–1949), a Danish physicist who taught and conducted research at the Technical University of Denmark.
In fluid dynamics, the Knudsenequation is used to describe how gas flows through a tube in free molecular flow. When the mean free path of the molecules...
from ensemble averaging Einstein’s equation over a large enough number of molecules N. Knudsen flow Knudsenequation Atomic diffusion Mass diffusivity...
Knudsen flow, Knudsen diffusion, Knudsen number, Knudsen layer and Knudsen gases. Also there is the Knudsenequation; two instruments, the Knudsen absolute...
solution thinly over a substrate, and evaporating the solvent. The Hertz–Knudsenequation is often used to estimate the rate of evaporation in these instances...
between particles becomes significant. Knudsenequation – Description of gas flow in free molecular flow Knudsen number – Dimensionless number relating...
equation Fokker–Planck equation Navier–Stokes equations Vlasov–Poisson equation Lattice Boltzmann methods List of paradoxes Martin Knudsen, "Die Gesetze der...
existence of the electromagnetic waves predicted by James Clerk Maxwell's equations of electromagnetism. The unit of frequency, cycle per second, was named...
equilibrium, solution of the Boltzmann equation can be represented by an asymptotic expansion in powers of Knudsen number (the Chapman–Enskog expansion)...
Cubic equations of state are a specific class of thermodynamic models for modeling the pressure of a gas as a function of temperature and density and...
for larger Knudsen numbers. The Navier–Stokes equations (named after Claude-Louis Navier and George Gabriel Stokes) are differential equations that describe...
near vortex lines Kirchhoff equationsKnudsenequation – Description of gas flow in free molecular flow Manning equation – Estimate of velocity in open...
Price equation (also known as Price's equation or Price's theorem) describes how a trait or allele changes in frequency over time. The equation uses a...
of gas molecules relative to the size of the gas gap, as given by the Knudsen number K n {\displaystyle K_{n}} . To quantify the ease with which a particular...
Archived from the original on 30 March 2009. Retrieved 7 April 2009. Knudsen, Lara (2006). Reproductive Rights in a Global Context. Vanderbilt University...
hypersonic flows (usually defined as those with a Knudsen number above 0.1) do not follow the Navier–Stokes equations.[citation needed] Hypersonic flows are typically...
probabilistic Monte Carlo simulation to solve the Boltzmann equation for finite Knudsen number fluid flows. The DSMC method was proposed by Graeme Bird...
liquid bath. Very low vapor pressures of solids can be measured using the Knudsen effusion cell method. In a medical context, vapor pressure is sometimes...
temperatures is generally found to be well predicted by the Arrhenius equation: D = D 0 exp ( − E A R T ) {\displaystyle D=D_{0}\exp \left(-{\frac...
correct at high Knudsen numbers. The Cunningham slip correction factor allows predicting the drag force on a particle moving a fluid with Knudsen number between...
minipermeameter device. A more accurate correction factor can be obtained using Knudsen correction. When using nitrogen gas for core plug measurements, the Klinkenberg...
moving, the more likely they are to pass through the effusion orifice. The Knudsen effusion cell is used to measure the vapor pressures of a solid with very...
(CFD) methods for fluid simulation. Instead of solving the Navier–Stokes equations directly, a fluid density on a lattice is simulated with streaming and...
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