MathLiveFick's first law of diffusion
Gives the diffusive flux of a species as proportional to the negative gradient of its concentration, with the mass diffusivity as the constant of proportionality. It is used to model diffusion in gases, liquids and solids when the concentration profile is known.
\mathbf{J}_{\mathrm{B}} = -D \nabla C_{\mathrm{B}}What the symbols mean
| molecular concentration of species B (mol/m^3) | |
| local average velocity of species B molecules (m/s) | |
| diffusive flux of species B, equal to C_{\mathrm{B}}\langle \boldsymbol{v}_{\mathrm{B}} \rangle (mol/(m^2·s)) | |
| mass diffusivity (m^2/s) | |
| gradient operator (spatial derivative vector) |
About this formula
- FieldPhysics
- TopicTransport phenomena
- LevelUniversity
- Also calledFick's first law, diffusion flux equation, mass diffusivity formula, diffusion coefficient equation, Fick's law of diffusion, molecular diffusion flux
- SourceWikidata Q604008
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