Crystal dissolution and precipitation in porous ...

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XVI International Conference on Computational Methods in Water Resources (CMWR-XVI) Ingeniørhuset

Crystal dissolution and precipitation in porous media: the case of fixed geometry
Author:Hans van Duijn <> (Technische Universiteit Eindhoven)
Tycho van Noorden <> (Technische Universiteit Eindhoven)
Iuliu Sorin Pop <> (Technische Universiteit Eindhoven)
Presenter:Iuliu Sorin Pop <> (Technische Universiteit Eindhoven)
Date: 2006-06-18     Track: Special Sessions     Session: Multi-Disciplinary Approaches To Reactive Transport Simulation In Aquifer Systems

In this talk we propose a pore scale model for precipitation and dissolution in porous media. We assuming that a fluid is flowing through the pores. Dissolved cations and anions are transported by the fluid. These ions can precipitate and form a crystalline solid, which is attached to the surface of the porous skeleton, and thus is immobile. The reverse reaction of dissolution is also possible. The proposed model includes the following components: the Stokes flow and the transport of the dissolved ions by convection and diffusion, which are processes in the void space of the medium, and the dissolution/precipitation reactions occurring on the surface of the grains (the porous skeleton). We pay a special attention to the dissolution rate, which is modelled by a Heaviside type graph and thus is multivalued. Here we assume that the flow geometry as well as the fluid properties are not affected by the chemical processes. The case of variable geometry is considered in another presentation given at this conference. We start with some qualitative properties of the model for general domains, and then consider simpler geometries. In particular, if the void space is a strip, with dissolution and precipitation occurring at the lateral boundaries, we investigate the formation of a dissolution front. Further, as a first step for a rigorous derivation of the macroscopic model we let the ratio between the thickness and the length of the strip vanish. We end up with the upscaled transport--reaction model proposed by C.J. van Duijn and P. Knabner. We conclude our talk with numerical experiments sustaining the theoretical results. Some details concerning the numerical algorithm will also be presented.