PLIC-based contact line modeling for simulations of droplet impact onto smooth and structured surfaces

We present a robust combination of methods for a Volume-of-Fluid (VoF) framework to investigate the influence of wettability on droplet impact onto grooved surfaces, with a particular focus on under-studied hydrophilic cases. The numerical method employs a three-phase PLIC interface reconstruction and utilizes the method of Sussman (2001) to model the contact line. This approach is shown to be compatible with both the balanced Continuum Surface Force (b-CSF) and Continuum Surface Stress (CSS) surface tension models. A mesh-dependent dynamic contact angle model based on Cox’s theory is implemented, demonstrating improved grid convergence over standard no-slip conditions. The framework is validated extensively against analytical solutions for sessile drops and static menisci, as well as new experimental data for droplet impacts on both smooth and grooved surfaces. The simulations successfully reproduce the experimental spreading dynamics, though we also highlight significant discrepancies between commonly used dynamic contact angle models and experimental measurements, especially during the receding phase. Finally, a parameter study varying the contact angle from 10° to 150° reveals that spreading transversal to the grooves is almost independent of wettability. Conversely, spreading parallel to the grooves is strongly affected by wettability, behaving similarly to spreading on a smooth substrate. In accordance with theory, it is found that at contact angles of 45° and below, corner flow governs the spreading inside the grooves.