Unsteady Burgers-vortex core radius
= Unsteady Burgers-vortex core radius
{title2=$\delta^2(t)=4\nu/\alpha+(\delta_0^2-4\nu/\alpha)e^{-\alpha t}$}
An axisymmetric Gaussian <Burgers vortex> with constant <circulation> in axial strain $\alpha$ has core area parameter $s=\delta^2$ satisfying $\dot s+\alpha s=4\nu$. Thus $s=4\nu/\alpha+(s_0-4\nu/\alpha)e^{-\alpha t}$, an attracting balance of transverse compression and viscous diffusion for every positive finite initial radius.