InterPore2025

Mechanisms for Enhanced Mixing in Unsaturated Porous Media

20 May 2025, 11:50

15m

Oral Presentation (MS06-A) Physics of multiphase flow in diverse porous media MS06-A

Speaker

Saif allah Farhat (University of Notre Dame)

Description

The coexistence of multiple immiscible fluids in porous media alters velocity distributions, creating dead-end regions and high-velocity channels that significantly affect solute transport, mixing, and reactivity in both natural and industrial systems. To investigate this at the pore-scale, we simulate the simultaneous flow of two immiscible fluids, air and water, using OpenFOAM. Our study includes a set of high-resolution, 2-D and 3-D numerical simulations in granular porous media. Multiple saturation degrees are simulated using a method that allows precise control over the desired saturation degree. Once the phases are stationary, we simulate conservative transport across a broad range of Peclet numbers. The resulting scalar field forms an advancing mixing front, which can be interpreted to predict mixing-limited reactions.

In this work, we primarily focus on the deformation of the mixing interface and pore-scale concentration fluctuations, which are widely recognized as key drivers for global reaction kinetics. Our analysis distinguishes between mixing in dead-end regions and transmitting pores, highlighting how trapping in dead-end regions becomes a significant mixing mechanism at lower water saturation levels. Furthermore, we observe that persistent concentration gradients in transmitting pores significantly enhance interface deformation, further contributing to mixing. We develop and validate a theoretical model that quantifies the effects of solute trapping and mixing within dead-end regions, as well as mixing interface deformation in transmitting pores. Lastly, we evaluate the impact of dimensionality (2D vs. 3D) on mixing across different saturation levels, which is particularly important in unsaturated systems, where the connectivity of fluid phases in 2D flow domains is highly sensitive to saturation changes. Under the same unsaturated conditions and Peclet number, 3D systems show significantly less mixing enhancement than 2D systems.