Modeling Interactions and Dynamic Saturation Processes in Karst Media

Abstract The simulation of karst aquifers is highly challenging due to complex conduit‐matrix interactions. This study utilizes KarstFOAM, a high‐fidelity, physics‐based numerical model, to address these challenges. KarstFOAM integrates (a) a unified single‐domain Forchheimer–Darcy–Brinkman–Stokes (FDBS) formulation that transitions naturally across flow regimes, (b) benchmark‐level reproduction of interface‐scale features (velocity slip and a finite transition layer), and (c) a VOF‐based two‐phase treatment enabling conduit drying and variably saturated dynamics coupled to matrix retention effects. The model was validated against analytical solutions, laboratory experiments, and applied to a typical karst field site. Results demonstrate that KarstFOAM accurately simulates the conduit‐matrix interface velocity and transition zone, as well as dynamic saturation, conduit drying, and matrix water retention effects. The model shows high accuracy for single rainfall events (NSE ≈ 0.97). Given this high fidelity, the model is best suited for academic research requiring precise analysis of local physical mechanisms, rather than for regional water resource management. Future work will focus on developing simplified versions to achieve a better balance between scientific insight and practical application.