Retraction of the dissolution front in natural porous media. Yang, Y., Bruns, S., Rogowska, M., Hakim, S., S., Hammel, J., U., Stipp, S., L., S., & Sørensen, H., O. Sci. Rep., 8:5693, 2018.
Retraction of the dissolution front in natural porous media [pdf]Paper  abstract   bibtex   
The dissolution of porous materials in a flow field controls the fluid pathways through rocks and soils and shapes the morphology of landscapes. Identifying the dissolution front, the interface between the reactive and the unreactive volumes in a dissolving medium, is a prerequisite for describing dissolution-induced structure emergence and transformation. Despite its fundamental importance, the report on the dynamics of a dissolution front in an evolving natural microstructure is scarce. Here we show an unexpected, spontaneous migration of the dissolution front against the flow direction. This retraction stems from infiltration instability induced surface generation, which leads to an increase in reactive surface area when a porous medium dissolves in an imposing flow field. There is very good agreement between observations made with in situ, X-ray tomography and model predictions. Both show that the value of reactive surface area reflects a balance between flow-dependent surface generation and destruction, i.e. the " dry " geometric surface area of a porous material, measured without a flow field, is not necessarily the upper limit of its reactive surface area when in contact with reactive flow. This understanding also contributes to reconciling the discrepancies between field and laboratory derived solid-fluid reaction kinetics. In a reacting porous medium, a reaction front is an isosurface over which the chemical affinity of a reac-tion reduces to zero in the velocity direction. This isosurface separates the reacting surface from the remain-ing geometric surface and is the ideal boundary of the region of interest (ROI), for measuring the kinetics of water-rock interactions. At any given instant, the inherent heterogeneities of natural porous materials that are not encompassed by this isosurface do not contribute to the chemical reaction. Therefore, the ability to track an evolving reaction front can greatly simplify the analysis of many geochemical processes by allowing unambiguous identification of the temporal ROI. The dissolution front is the reaction front of a solid dissolution reaction. In a dissolving medium with a pres-sure driven flow field, there is a positive feedback between the mineral dissolution rate and the local permeability (Yang, Y. et al., Submitted, 2017) 1,2
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 abstract = {The dissolution of porous materials in a flow field controls the fluid pathways through rocks and soils and shapes the morphology of landscapes. Identifying the dissolution front, the interface between the reactive and the unreactive volumes in a dissolving medium, is a prerequisite for describing dissolution-induced structure emergence and transformation. Despite its fundamental importance, the report on the dynamics of a dissolution front in an evolving natural microstructure is scarce. Here we show an unexpected, spontaneous migration of the dissolution front against the flow direction. This retraction stems from infiltration instability induced surface generation, which leads to an increase in reactive surface area when a porous medium dissolves in an imposing flow field. There is very good agreement between observations made with in situ, X-ray tomography and model predictions. Both show that the value of reactive surface area reflects a balance between flow-dependent surface generation and destruction, i.e. the " dry " geometric surface area of a porous material, measured without a flow field, is not necessarily the upper limit of its reactive surface area when in contact with reactive flow. This understanding also contributes to reconciling the discrepancies between field and laboratory derived solid-fluid reaction kinetics. In a reacting porous medium, a reaction front is an isosurface over which the chemical affinity of a reac-tion reduces to zero in the velocity direction. This isosurface separates the reacting surface from the remain-ing geometric surface and is the ideal boundary of the region of interest (ROI), for measuring the kinetics of water-rock interactions. At any given instant, the inherent heterogeneities of natural porous materials that are not encompassed by this isosurface do not contribute to the chemical reaction. Therefore, the ability to track an evolving reaction front can greatly simplify the analysis of many geochemical processes by allowing unambiguous identification of the temporal ROI. The dissolution front is the reaction front of a solid dissolution reaction. In a dissolving medium with a pres-sure driven flow field, there is a positive feedback between the mineral dissolution rate and the local permeability (Yang, Y. et al., Submitted, 2017) 1,2},
 bibtype = {article},
 author = {Yang, Y and Bruns, S and Rogowska, M and Hakim, S S and Hammel, J U and Stipp, S L S and Sørensen, H O},
 journal = {Sci. Rep.}
}
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