arXiv subjects

Anna L. Herring

Publications and source records attributed to Anna L. Herring.

3 recordsLinked to original sources

arXiv2026

Quantifying Injection-Driven Interphase Mass Transfer within Porous Media via Time-Elapsed X-ray micro-Computed Tomography

Understanding interphase mass transfer is essential for a variety of applications in porous media, ranging from groundwater remediation to geologic energy storage. While X-ray micro-Computed Tomography ($μ$CT) provides critical \textit{in situ} observations, its application in quantifying mass transfer phenomena requires models and workflows compatible with spatial and temporal constraints. Current literature presents three analytical frameworks for evaluating interphase mass transfer using time-lapsed sequences of $μ$CT scans: the Slice-Averaged Concentration (SAC) approach, the Non-Classified per-Cluster (NPC) approach, and the Classified per-Cluster (CPC) approach. Comparing results with previous studies, we identify that further research is needed to understand how these approaches will vary with experimental conditions and how the physical implications of their calculation frameworks should affect the interpretation of the results, as there are often no ground-truth measurements to compare the estimates to. The current study systematically evaluates the frameworks and results of the three approaches as applied to several sequences of time-lapsed $μ$CT scans, each observing hydrogen dissolution experiments at varying injection rates. For each observed advective injection rate, results indicate that system-scale properties, like mass transfer, appear robust to the selected approach. However, approach estimates diverged when approximating more complex, pore-scale phenomena, such as aqueous solute concentration. Ultimately, the utility of one approach over another is determined by the desired level of system detail, at the cost of the computational resources required to achieve it. Our results provide a framework for researchers to select analytical approaches based on available computational resources and the desired level of physical detail.

physics.flu-dyn↗

arXiv2020

Characterization of wetting using topological principles

Hypothesis Understanding wetting behavior is of great importance for natural systems and technological applications. The traditional concept of contact angle, a purely geometrical measure related to curvature, is often used for characterizing the wetting state of a system. It can be determined from Young's equation by applying equilibrium thermodynamics. However, whether contact angle is a representative measure of wetting for systems with significant complexity is unclear. Herein, we hypothesize that topological principles based on the Gauss-Bonnet theorem could yield a robust measure to characterize wetting. Theory and Experiments We introduce a macroscopic contact angle based on the deficit curvature of the fluid interfaces that are imposed by contacts with other immiscible phases. We perform sessile droplet simulations followed by multiphase experiments for porous sintered glass and Bentheimer sandstone to assess the sensitivity and robustness of the topological approach and compare the results to other traditional approaches. Findings We show that the presented topological principle is consistent with thermodynamics under the simplest conditions through a variational analysis. Furthermore, we elucidate that at sufficiently high image resolution the proposed topological approach and local contact angle measurements are comparable. While at lower resolutions, the proposed approach provides more accurate results being robust to resolution-based effects. Overall, the presented concepts open new pathways to characterize the wetting state of complex systems and theoretical developments to study multiphase systems.

physics.flu-dyn↗

arXiv2019

Linking continuum-scale state of wetting to pore-scale contact angles in porous media

Wetting phenomena play a key role in flows through porous media. Relative permeability and capillary pressure-saturation functions show a high sensitivity to wettability, which has different definitions at the continuum- and pore-scale. At the continuum-scale, the state of wetting is defined as Amott-Harvey or USBM (United States Bureau of Mines) by capillary pressure drainage and imbibition cycles. At the pore-scale, the concept of contact angle is used, which until recently was not experimentally possible to determine within an opaque porous medium. Recent progress on measurements of pore-scale contact angles by X-ray computed micro-tomography has therefore attracted significant attention in various research communities. In this work, the Gauss-Bonnet theorem is applied to provide a direct link between capillary pressure saturation $P_c(S_w)$ data and measured distributions of pore-scale contact angles. We propose that the wetting state of a porous medium can be described in terms of geometrical arguments that constrain the morphological state of immiscible fluids. The constraint describes the range of possible contact angles and interfacial curvatures that can exist for a given system. We present measurements in a tested sandstone for which the USBM index, $P_c(S_w)$, and pore-scale contact angles are measured. Additional studies are also performed using two-phase Lattice Boltzmann simulations to test a wider range of wetting conditions. We show that mean pore-scale contact angle measurements can be predicted from petrophysical data within a few differences. This provides a general framework on how continuum-scale data can be used to describe the geometrical state of fluids within porous media.

physics.flu-dyn↗