Improving capillary flow predictions in self-healing concrete: a dynamic contact angle approach using the volume of fluid model

Abstract

This study proposes an enhanced Volume of Fluid (VOF) model incorporating dynamic contact angle (DCA) effects to improve capillary flow predictions in encapsulation-based self-healing concrete. While the classical Lucas-Washburn equation (LWE) assumes a constant contact angle, leading to overestimations in capillary rise, this work integrates time-dependent (TDCA) and velocity-dependent (VDCA) DCA models to better capture interfacial dynamics at the meniscus. Simulations demonstrated that the VDCA model reduced mean absolute errors from 17.0 to 42.9% (constant angle) to 3.1–5.3%, aligning closely with experimental data and modified LWE predictions. Oscillations around equilibrium heights, prevalent in constant-angle simulations, were significantly mitigated, though minor inertial effects persisted in wider cracks (e.g., 1 mm). The VDCA framework also extended applicability across crack widths (0.261–1 mm), offering flexibility beyond the TDCA model’s geometry-specific limitations. However, validation was restricted to water in planar cracks, highlighting the need for future parameterization of non-Newtonian agents (e.g., polymers) and complex crack geometries. This work advances capillary flow modeling in self-healing systems by emphasizing the necessity of dynamic wetting behavior, while underscoring the importance of substrate-fluid calibration for real-world implementation.