Diffusion Courant number
= Diffusion Courant number
{title2=$r=\nu\Delta t/(\Delta x)^2$}
The diffusion <Courant number> is $r=\nu k/d^2$ for diffusivity $\nu$, time step $k$ and spatial step $d$. Keeping $r$ fixed is a <parabolic mesh refinement>. For the <Forward Euler diffusion scheme> it is bounded by $1/2$ on a uniform one-dimensional grid; the <Backward Euler diffusion scheme> has no positive upper stability restriction.