Speaker
Description
Mixing of solutes in porous media is controlled by the complex interaction between advection, diffusion and pore scale heterogeneity. While many studies focus on bulk metrics such as breakthrough curves, the impact of the microscopic (pore-scale) controlling mechanisms under confinement and the detailed structure of the mixing front – where concentration gradients and scalar dissipation are highest – are not yet fully understood. The main challenge is the upscaling of mixing confinement: the microscopic quantities that characterize such condition are two-fold: i) no-slip (for flow) and no-flux (for solute transport) at solid grain walls. To address this we performed numerical simulations and experiments based on microfluidics and time-lapse video microscopy. These complementary datasets along with image-based analysis allow us to capture detailed spatial-temporal evolution of diagnostic parameters (such as scalar dissipation rate, concentration and gradients statistical distributions, PDF) to quantify mixing in heterogeneous and confined environments. We track the mixing front evolution by detection of mixing “ridges”: lines of locally maximal gradients that indicate the active mixing front location. This allows us to quantify the mixing dynamics which results not to be properly described by the lamellar approach recently extended to porous systems at continuous (Darcy) scale. These findings highlight the impact of the detailed porous structure and the associated need for new models that, taking into account the pore-scale organization, capture macroscopic mixing in heterogeneous porous systems.
| Country | Switzerland |
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