TY - JOUR
T1 - Explaining persistent incomplete mixing in multicomponent reactive transport with Eulerian stochastic model
AU - Tartakovsky, Alexandre M.
AU - Barajas-Solano, David
N1 - Publisher Copyright:
© 2020
PY - 2020/11
Y1 - 2020/11
N2 - We present an Eulerian stochastic advection–diffusion–reaction (SADR) model and use it to explain incomplete mixing typically observed in transport experiments with bimolecular reactions. Unlike traditional advection–dispersion–reaction (ADR) models, the SADR model describes mechanical and diffusive mixing as two separate processes. In the SADR model, mechanical mixing is driven by random advective velocity whose variance is given by the coefficient of mechanical dispersion. The diffusive mixing is modeled as a Fickian diffusion process with the effective diffusion coefficient. We demonstrate that the sum of the two coefficients is equal to the dispersion coefficient, but only the effective diffusion coefficient contributes to the mixing-controlled reactions. We use experimental results of Gramling et al. ** to show that for transport and bimolecular reactions in porous media, the SADR model is significantly more accurate than the ADR model, which overestimates the concentration of the reaction product by as much as 60%. We also show that the SADR model predicts an experimentally observed bell-shaped spatial distribution of the reactive product concentration, while the ADR model results in a concentration distribution with an unphysical kink.
AB - We present an Eulerian stochastic advection–diffusion–reaction (SADR) model and use it to explain incomplete mixing typically observed in transport experiments with bimolecular reactions. Unlike traditional advection–dispersion–reaction (ADR) models, the SADR model describes mechanical and diffusive mixing as two separate processes. In the SADR model, mechanical mixing is driven by random advective velocity whose variance is given by the coefficient of mechanical dispersion. The diffusive mixing is modeled as a Fickian diffusion process with the effective diffusion coefficient. We demonstrate that the sum of the two coefficients is equal to the dispersion coefficient, but only the effective diffusion coefficient contributes to the mixing-controlled reactions. We use experimental results of Gramling et al. ** to show that for transport and bimolecular reactions in porous media, the SADR model is significantly more accurate than the ADR model, which overestimates the concentration of the reaction product by as much as 60%. We also show that the SADR model predicts an experimentally observed bell-shaped spatial distribution of the reactive product concentration, while the ADR model results in a concentration distribution with an unphysical kink.
KW - Bimolecular reactions
KW - Incomplete mixing
KW - Mechanical mixing
KW - Stochastic transport model
KW - Tracer test
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U2 - 10.1016/j.advwatres.2020.103729
DO - 10.1016/j.advwatres.2020.103729
M3 - Article
AN - SCOPUS:85089673453
SN - 0309-1708
VL - 145
JO - Advances in Water Resources
JF - Advances in Water Resources
M1 - 103729
ER -