Quantifying the Flow Dynamics of Water-Air Flow in Dual-Porosity Micromodels Using Micro-PIV

Multiphase flow in porous media is central to a broad range of natural and engineering applications, including oil recovery, CO₂ storage, and critical zone science. Many of these porous solid matrices display multi-scale variability in pore structure and physical properties such as porosity and permeability. For instance, in critical zone, soil is often viewed as a hierarchical organization: primary particles form aggregates, which in turn form macroaggregates, effectively leading to a dual-porosity medium. The resultant multi-scale flow dynamics and inter-/intra-aggregate interaction in this system are recognized to control numerous processes, such as water and gaseous transport. However, the underlying physics is not well understood from a fluid mechanics perspective. To that end, the multi-phase flow of air and water is investigated using a novel 2D dual-porosity microfluidic device, with a focus on the multi-scale interaction and the role of corner film flows. The microfluidic device, constructed in a glass-silicon-glass architecture, offers precise structure and excellent optical access. The micro-PIV measurement provides valuable insight into the flow dynamics at both micro- and macro-scales simultaneously enabled by an innovative dual-magnification imaging system.