Streamline diffusion
This article has multiple issues. Please help improve it or discuss these issues on the talk page.
|
Streamline diffusion, given an advection-diffusion equation, refers to all diffusion going on along the advection direction.
Explanation
If we take an advection equation, for simplicity of writing we have assumed \(\nabla\cdot{\bold u}=0\), and \(||{\bold u}||=1\) \[ \frac{\partial\psi}{\partial t} +{\bold u}\cdot\nabla\psi=0. \]
we may add a diffusion term, again for simplicty, we assume the diffusion to be constant over the entire field.
\[D\nabla^2\psi\],
Giving us an equation of the form:
\[ \frac{\partial\psi}{\partial t} +{\bold u}\cdot\nabla\psi +D\nabla^2\psi =0 \]
We may now rewrite the equation on the following form:
\[ \frac{\partial\psi}{\partial t} +{\bold u}\cdot \nabla\psi +{\bold u}({\bold u}\cdot D\nabla^2\psi) +(D\nabla^2\psi-{\bold u}({\bold u}\cdot D\nabla^2\psi)) =0 \]
The term below is called streamline diffusion. \[{\bold u}({\bold u}\cdot D\nabla^2\psi)\]
Crosswind diffusion
Any diffusion orthogonal to the streamline diffusion is called crosswind diffusion, for us this becomes the term: \[ (D\nabla^2\psi-{\bold u}({\bold u}\cdot D\nabla^2\psi)) \]
40x30px | This mathematics-related article is a stub. You can help Oilfield Wiki by expanding it. |