Diffusion Equation in 2D two-dimensional euclidian space ℝ2
Planar diffusion equation with axial symmetric property distribution:
\frac{\partial {\rm w}}{\partial t} = \frac{\partial {\rm w}^2}{\partial^2 r} + \frac{1}{r} \frac{\partial {\rm w}}{\partial r}
where
[ Planar diffusion equation ]