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

Explanation

In an advection equation, for simplicity assume: , and

Adding a diffusion term, again for simplicity, assume the diffusion to be constant over the entire field.

,

Giving an equation of the form:

The equation may now be rewritten in the following form:

The term below is called streamline diffusion.

Crosswind diffusion

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



This article uses material from the Wikipedia article Streamline diffusion, which is released under the Creative Commons Attribution-Share-Alike License 3.0.