Hydrodynamics of micron-scale particle impact on thin liquid films bounded by dual gas–liquid interfaces: Mode transitions and critical velocity prediction

Understanding the capture mechanisms of micrometer-sized dust particles by thin liquid films is critical for industrial filtration and agricultural irrigation systems. However, existing research predominantly focuses on millimeter-scale particles impacting on single gas–liquid interfaces. This study employs numerical simulations to systematically investigate the dynamic water entry and exit processes, interfacial deformation, and wetting behaviors of micrometer-sized particles impacting on dual-interface liquid films. The results indicate that increased hydrophobicity minimizes viscous dissipation and contact line pinning, thereby expanding the rebound regime. The critical velocity for impact mode transition decreases with decreasing R and lower surface tension but increases with higher contact angles and higher liquid film viscosity. When the liquid film is relatively thick, the particle is primarily subjected to the surface tension of a single interface during the initial impact stage. In contrast, for a thin liquid film, the two interfaces deform asynchronously throughout the impact process, leading to differential surface tension effects on the particle. A semi-empirical formula for the critical velocity was derived and validated based on numerical simulations. The formula not only accounts for the asynchronous deformation of the liquid films on both sides but also incorporates a correction factor for the Ohnesorge number.