diffusion
(the spreading of particles toward an even distribution)
Diffusion is the net movement of particles such as atoms or
molecules from areas of higher concentration to areas of lower
concentration. If there is some random particle motion within a fluid
producing random walks, diffusion occurs.
A diffusion equation is an equation describing diffusion
over time. Fick's laws include a diffusion equation describing
what happens in many cases, a type of diffusion termed
Fickian diffusion. The equation:
dC
J = -D ——
dx
- J - the diffusive flux, the flow of the diffusing substance as amount of substance/unit time through a unit area.
- D - the diffusion coefficient (aka diffusivity) of the substance.
- C - the concentration of the diffusing material, as in amount of substance per unit volume.
- x - measurement over a direction over which we are describing the diffusion.
Amount of substance is a measure of the number of particles
(atoms or molecules) of the substance,
quantified in moles, for example.
(physics,chemistry)
Further reading:
https://en.wikipedia.org/wiki/Diffusion
https://en.wikipedia.org/wiki/Fick%27s_laws_of_diffusion
http://mathbench.umd.edu/modules/cell-processes_diffusion/page09.htm
https://serc.carleton.edu/NAGTWorkshops/mineralogy/mineral_physics/diffusion.html
Referenced by pages:
atmospheric escape
diffusion damping
Eddington approximation
radiation zone
stellar evolution
two-stream approximation
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