On the impact of pore water flow on the induced polarization signature of porous media
E001
Abstract
Induced polarization (IP) is increasingly applied for hydrological, environmental, and agricultural purposes. Understanding the relationship between the IP signature and porous media properties is crucial for accurate data interpretation. Traditional mechanistic models of the IP phenomenon rely on the Poisson-Nernst-Planck equations, emphasizing diffusion and electromigration fluxes as the primary drivers of charge transport. However, the impact of advection flux on IP has not been investigated experimentally or included in existing models.
This study measures the spectral IP (SIP) signature of porous media under varying flow conditions and develops a model that incorporates fluid flow into the SIP analysis. Our experimental and modeling results reveal that as bulk fluid velocity increases, both polarization and relaxation times decrease. The numerical model indicates that fluid flow near particles deforms the electrical double layer (EDL) structure, leading to the observed reduction in polarization. While the model qualitatively aligns with the experimental data, it tends to overestimate the impact of flow rate on the SIP signature, likely due to flow boundary conditions.
Overall, our findings demonstrate the significant sensitivity of the SIP signature to fluid flow, underscoring the necessity of considering fluid velocity in SIP interpretations. This work opens an exciting new direction for noninvasive measurements of fluid flow at the EDL scale, enhancing the understanding and application of SIP in various environmental and hydrological contexts.