Soft Matter and Complex Systems Seminar

One of the mechanisms of pattern formation in hydrogeochemical systems is the reactive-infiltration instability, which occurs whenever a porous rock undergoes dissolution due to exposure to a constant inflow of reactants brought by the infiltrating fluid. As a result of positive feedbacks between the flow, reactant transport and matrix evolution, planar dissolution fronts are inherently unstable and spontaneously break up, leading to the formation of highly porous flow paths, dubbed "wormholes". The phenomenon has been studied by a number of authors and is already quite well understood.

In natural systems, however, dissolution of the minerals in the primary rock is often accompanied by reprecipitation of the dissolution products, which form secondary minerals. Contrary to simple dissolution, the porosity profiles in this case are in general non-monotonic. Performing linear stability analysis of the model stationary reaction front, we show that the dissolution-precipitation fronts can also be unstable, even if the secondary rock is even less porous (and less permeable) than the primary one. We also present the fully nonlinear evolution of the system, studied by numerical simulations.