Drainage volume decay in a dipole porous current
= Drainage volume decay in a dipole porous current
{title2=$V\propto t^{-1/4}$}
For the <dipole similarity solution of a draining porous current>, $V=\phi\int h\,dx=\phi ad\,t^{-1/4}/18$. Thus $\dot V/V=-1/(4t)$. A shifted similarity origin replaces $t$ by $t+t_0$. Neither a positive rate nor a rate $-1/(2t)$ is compatible with this two-dimensional first-moment-conserving profile.