Phase-field modeling of capillary barrier effects: Roles of flow orientation relative to gravity and invasion velocity
Abstract
Capillary barrier effects hinder water migration across textural contrasts in layered porous media, with significant implications for geotechnical and geological practice. In this study, the phase-field method was applied to simulate capillary barrier effects at the micro-scale, focusing on the roles of flow orientation relative to gravity (normal, assisted, and opposed) and invasion velocity. The results showed that in the capillary-dominated regime at low velocities, the capillary barrier effect was highly sensitive to flow orientation: It effectively retained water in the fine-pore region when gravity was normal to or opposed the flow, but was substantially weakened when gravity assisted the flow. In the viscous-dominated regime at high velocities, viscous forces dominated over capillary and gravitational effects, suppressing the capillary barrier effect and producing similar invasion patterns across all flow orientations. Quantitative saturation analysis indicated that, under low-velocity conditions, the fine-pore region saturation at both the arrival and breakthrough of the invading front at the fine-coarse interface was highest for gravity-opposed flow, intermediate for gravity-normal flow, and lowest for gravity-assisted flow. These differences diminished and converged as velocity increased. The maximum net enhancement in fine-pore region saturation occurred under low-velocity, gravity-normal conditions. These findings provide microscopic insights into the interplay among capillary, viscous, and gravitational forces governing capillary barrier effect behavior, and offer a scientific basis for understanding water redistribution in layered porous systems.
Document Type: Original article
Cited as: Li, G., Ye, H., Gong, W., Zhan, L., Du, X. Phase-field modeling of capillary barrier effects: Roles of flow orientation relative to gravity and invasion velocity. Capillarity, 2026, 20(3): 86-98. https://doi.org/10.46690/capi.2026.09.03
DOI:
https://doi.org/10.46690/capi.2026.09.03Keywords:
Capillary barrier effect, phase-field method, layered porous media, flow orientation, invasion velocityReferences
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Copyright (c) 2026 Guangyao Li, Huangliang Ye, Wentao Gong, Liangtong Zhan, Xiuli Du
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