Differential diffusive instabilities of miscible two-layer stratifications in porous media and Hele-Shaw cells

In porous media, a stratification of a given solution on top of another miscible solution can be buoyantly unstable because of an unstable density stratification or because of differential diffusive effects. The former is the well known Rayleigh–Taylor (RT) mechanism wherein the interface is destabilized by the denser solution overlying a less...