Phase Saturation Control on Vorticity Enhances Mixing in Porous Media
Abstract Mixing controls the fate of any solute entering porous media. Hence, an understanding of the involved processes is essential for assessing subsurface contamination and planning for its protection. However, the three‐dimensional mechanisms dominating solute mixing in the presence of several...
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| Format: | Article |
| Language: | English |
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Wiley
2024-04-01
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| Series: | Water Resources Research |
| Online Access: | https://doi.org/10.1029/2023WR036628 |
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| author | Andrés Velásquez‐Parra Federica Marone Rolf Kaufmann Michele Griffa Joaquín Jiménez‐Martínez |
| author_facet | Andrés Velásquez‐Parra Federica Marone Rolf Kaufmann Michele Griffa Joaquín Jiménez‐Martínez |
| author_sort | Andrés Velásquez‐Parra |
| collection | DOAJ |
| description | Abstract Mixing controls the fate of any solute entering porous media. Hence, an understanding of the involved processes is essential for assessing subsurface contamination and planning for its protection. However, the three‐dimensional mechanisms dominating solute mixing in the presence of several fluid phases in the pore space, and their dependency on phase saturation degree (fraction of the pore volume occupied by a phase) are unknown. Here, we analyze solute mixing in unsaturated porous media at the pore scale using X‐ray micro‐tomography performed with synchrotron radiation at unprecedented temporal and spatial resolutions for such an investigation. Transport experiments through a synthetic, sand‐like porous medium, followed in 4D using a contrast solution, are performed at different liquid phase saturation degrees. The results reveal larger solute's front deformation at lower saturation, which translates into an enhanced mixing with time. Using different topological indexes, defined based on a description of the liquid phase geometry and of the resulting hydrodynamics, we show an increase in the spatial convergence of flow streamlines at lower saturation, which, in turn, leads to a strengthened helical flow inside the liquid phase. Consequently, this increases the number of shear‐ and vorticity‐dominated deformation regions, as characterized by larger negative and positive Q‐criterion values, respectively. These findings represent a major step toward understanding the control of both saturation and the system's heterogeneity on solute mixing, essential, among others, to assess reactivity in porous media. |
| format | Article |
| id | doaj-art-1ca0f6d73a1b484495af80d13971e65a |
| institution | OA Journals |
| issn | 0043-1397 1944-7973 |
| language | English |
| publishDate | 2024-04-01 |
| publisher | Wiley |
| record_format | Article |
| series | Water Resources Research |
| spelling | doaj-art-1ca0f6d73a1b484495af80d13971e65a2025-08-20T02:09:24ZengWileyWater Resources Research0043-13971944-79732024-04-01604n/an/a10.1029/2023WR036628Phase Saturation Control on Vorticity Enhances Mixing in Porous MediaAndrés Velásquez‐Parra0Federica Marone1Rolf Kaufmann2Michele Griffa3Joaquín Jiménez‐Martínez4Department of Water Resources and Drinking Water Swiss Federal Institute of Aquatic Science and Technology, Eawag Dübendorf SwitzerlandSwiss Light Source, Paul Scherrer Institute, PSI Villigen SwitzerlandSwiss Federal Laboratories for Materials Science and Technology, Empa Dübendorf SwitzerlandSwiss Federal Laboratories for Materials Science and Technology, Empa Dübendorf SwitzerlandDepartment of Water Resources and Drinking Water Swiss Federal Institute of Aquatic Science and Technology, Eawag Dübendorf SwitzerlandAbstract Mixing controls the fate of any solute entering porous media. Hence, an understanding of the involved processes is essential for assessing subsurface contamination and planning for its protection. However, the three‐dimensional mechanisms dominating solute mixing in the presence of several fluid phases in the pore space, and their dependency on phase saturation degree (fraction of the pore volume occupied by a phase) are unknown. Here, we analyze solute mixing in unsaturated porous media at the pore scale using X‐ray micro‐tomography performed with synchrotron radiation at unprecedented temporal and spatial resolutions for such an investigation. Transport experiments through a synthetic, sand‐like porous medium, followed in 4D using a contrast solution, are performed at different liquid phase saturation degrees. The results reveal larger solute's front deformation at lower saturation, which translates into an enhanced mixing with time. Using different topological indexes, defined based on a description of the liquid phase geometry and of the resulting hydrodynamics, we show an increase in the spatial convergence of flow streamlines at lower saturation, which, in turn, leads to a strengthened helical flow inside the liquid phase. Consequently, this increases the number of shear‐ and vorticity‐dominated deformation regions, as characterized by larger negative and positive Q‐criterion values, respectively. These findings represent a major step toward understanding the control of both saturation and the system's heterogeneity on solute mixing, essential, among others, to assess reactivity in porous media.https://doi.org/10.1029/2023WR036628 |
| spellingShingle | Andrés Velásquez‐Parra Federica Marone Rolf Kaufmann Michele Griffa Joaquín Jiménez‐Martínez Phase Saturation Control on Vorticity Enhances Mixing in Porous Media Water Resources Research |
| title | Phase Saturation Control on Vorticity Enhances Mixing in Porous Media |
| title_full | Phase Saturation Control on Vorticity Enhances Mixing in Porous Media |
| title_fullStr | Phase Saturation Control on Vorticity Enhances Mixing in Porous Media |
| title_full_unstemmed | Phase Saturation Control on Vorticity Enhances Mixing in Porous Media |
| title_short | Phase Saturation Control on Vorticity Enhances Mixing in Porous Media |
| title_sort | phase saturation control on vorticity enhances mixing in porous media |
| url | https://doi.org/10.1029/2023WR036628 |
| work_keys_str_mv | AT andresvelasquezparra phasesaturationcontrolonvorticityenhancesmixinginporousmedia AT federicamarone phasesaturationcontrolonvorticityenhancesmixinginporousmedia AT rolfkaufmann phasesaturationcontrolonvorticityenhancesmixinginporousmedia AT michelegriffa phasesaturationcontrolonvorticityenhancesmixinginporousmedia AT joaquinjimenezmartinez phasesaturationcontrolonvorticityenhancesmixinginporousmedia |