Compound-specific local and effective transverse dispersion coefficients for conservative and reactive mixing in heterogeneous porous media
Chiogna G, Cirpka OA, Grathwohl P, Rolle M (2012)
Publication Type: Conference contribution
Publication year: 2012
Book Volume: 355
Pages Range: 163-168
Conference Proceedings Title: IAHS-AISH Publication
Event location: DEU
ISBN: 9781907161346
Abstract
Dilution in heterogeneous porous media can be quantified using different measures which lead to the definition of effective dispersion coefficients. These up-scaled parameters should account for both local-scale dispersion and effects of flow variability in heterogeneous formations (e.g. flow focusing in high-conductivity and defocusing in low-conductivity inclusions). The correct quantification of mixing is particularly important in order to model mixing-controlled reactions in porous media. Under steady-state conditions with continuous injection from a line source, 2D conservative and reactive solute transport simulations were performed. It was shown that different parameterizations of local transverse dispersion coefficients significantly affect the quantification of field-scale mixing processes. Bench-scale experiments showed a nonlinear dependence of local transverse dispersion on molecular diffusion over a wide range of flow velocities, implying compound-specific transverse mixing at the local Darcy scale. Heterogeneous field-scale scenarios were considered, characterized by different variability in the conductivity field, and a set of Monte Carlo simulations was performed. We quantified transverse mixing with different measures including effective transverse dispersion coefficients, scalar dissipation rates and the recently introduced flux-related dilution index and flux-related second central spatial moments. It was shown that quantities derived in a flux-related framework are affected by a lower degree of uncertainty and that, in the case of low to moderately heterogeneous porous media, the effective transverse dispersion coefficients are significantly different for different compounds. Effective transverse dispersion coefficients were found to be up to one order of magnitude larger than the local values due to mixing enhancement processes related to flow-focusing in high-permeability inclusions. In the case of mixing-controlled reactive transport, considering instantaneous complete bimolecular reactions, it was shown that compound-specific dispersion coefficients affect the prediction of the length of reactive solute plumes. Furthermore, the recently developed concept of critical dilution index was applied to quantify the amount of mixing required to completely degrade a reactive contaminant plume. Copyright © 2012 IAHS Press.
Involved external institutions
Italy (IT)
Germany (DE)How to cite
APA:
Chiogna, G., Cirpka, O.A., Grathwohl, P., & Rolle, M. (2012). Compound-specific local and effective transverse dispersion coefficients for conservative and reactive mixing in heterogeneous porous media. In IAHS-AISH Publication (pp. 163-168). DEU.
MLA:
Chiogna, Gabriele, et al. "Compound-specific local and effective transverse dispersion coefficients for conservative and reactive mixing in heterogeneous porous media." Proceedings of the 8th International Conference on Calibration and Reliability in Groundwater Modeling - Repositories of Knowledge, ModelCARE 2011, DEU 2012. 163-168.
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