CELLULAR-AUTOMATON MODEL OF PRECIPITATION DISSOLUTION COUPLED WITH SOLUTE TRANSPORT/

Precipitation/dissolution reactions coupled with solute transport are modeled as a cellular automaton in which solute molecules perform a ra ndom walk on a regular lattice and react according to a local probabil istic rule. Stationary solid particles dissolve with a certain probabi lity and, provided solid is already present or the solution is saturat ed, solute particles have a probability to precipitate. In our simulat ion of the dissolution of a solid block inside uniformly flowing water we obtain solid precipitation downstream from the original solid edge , in contrast to the standard reaction-transport equations. The observ ed effect is the result of fluctuations in solute density and diminish es when we average over a larger ensemble. The additional precipitatio n of solid is accompanied by a substantial reduction in the relatively small solute concentration. The model is appropriate for the study of the role of intrinsic fluctuations in the presence of reaction thresh olds and can be employed to investigate porosity changes associated wi th the carbonation of cement.