Streamline diffusion

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Streamline diffusion, given an advection-diffusion equation, refers to all diffusion going on along the advection direction.

Explanation[edit]

If we take an advection equation, for simplicity of writing we have assumed , and

we may add a diffusion term, again for simplicty, we assume the diffusion to be constant over the entire field.

,

Giving us an equation of the form:

We may now rewrite the equation on the following form:

The term below is called streamline diffusion.

Crosswind diffusion[edit]

Any diffusion orthogonal to the streamline diffusion is called crosswind diffusion, for us this becomes the term: