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We study the fragmentation of pre-perforated thin liquid films using three-dimensional numerical simulations, focusing on droplet formation following hole collisions. An air–water system with film thickness e0=25  μm and varying hole spacings (dh/e0=3−20) is considered. The liquid bridge formed between colliding holes undergoes oscillation and stretching before breakup. The outcome depends on the spacing: for small dh, ligaments recoil into single droplets, while for larger dh, ligaments fragment via end-pinching and Rayleigh–Plateau (RP) instabilities. Droplet size distributions are compared with RP predictions and show improved agreement when a 40% reduction in ligament diameter due to stretching is accounted for. The results also compare favorably with experimental data from air-blasted films. This work provides new insight into the fundamental mechanisms controlling droplet formation from perforated films and highlights the critical role of hole spacing in determining ligament dynamics and droplet size distributions. 

This study explores the role of gas flow dynamics in the fragmentation of thin liquid sheets using three-dimensional numerical simulations. A thin liquid sheet with a thickness of 25 μm is subjected to high-velocity co-flowing gas streams characterized by three distinct gas Reynolds numbers, namely, Reg=300,500, and 1000. Simulations show that the breakup behavior of the sheet is governed by the vortical structures formed in the gas flow, which range from oblique vortex shedding at lower Reg to rib-like vortical patterns at higher Reg. The gas-induced instabilities impose transverse and longitudinal oscillations on the liquid sheet, which govern the locations of hole formation, the development of ligaments, and ultimately the resulting droplet size distribution. For Reg=300, breakup occurs via rim instability and the end-pinching or Rayleigh–Plateau-type instability of liquid fingers, whereas for Reg=500 and 1000, sheet rupture through hole formation and collision dominates. A manifold death (MD) algorithm is used to enforce breakup at a grid-independent critical film thickness, improving robustness against numerical artifacts. Droplet size distributions obtained with and without the MD algorithm confirm that the dominant droplet size remains unchanged, while the formation of small, potentially spurious droplets is suppressed. The resulting distributions align more closely with a lognormal model, consistent with the presence of multiple breakup mechanisms. This work provides new insight into the coupling between gas-phase instabilities and liquid fragmentation, offering a pathway to more accurate predictive models for air-blast atomization processes.