From crown splash to bell-shaped closure: Dynamics of laser-induced splashing on the liquid metal surface

This study combines high-speed imaging and multi-physics coupled numerical simulations to investigate the dynamic evolution and topological transition of free-surface splashing of Galinstan induced by nanosecond pulsed lasers. Within laser energies of 0.15–0.45 mJ and pulse durations of 150–350 ns, three sequential splashing regimes are observed experimentally with increasing laser pulse energy: open crown, transitional state, and closed bell-shaped crown. The fully closed crown with a steady central liquid column is reported for the first time in laser-induced liquid metal splashing. A compressible volume of fluid model accounting for vapor recoil pressure is established and validated against experiments. Flow-field analysis reveals that gas-phase recirculation vortices originating from the initial crater and pressure difference across the cavity dominate crown closure. A two-dimensional regime map is constructed using the crater aspect ratio γ* at laser pulse termination and equivalent Weber number We as coordinates. A simplified crater-liquid-film mechanical model is developed based on axisymmetric bell theory, yielding a critical criterion for bell-shaped closure. The theoretically predicted regime boundaries are qualitatively consistent with the experimental regime map. Furthermore, control experiments under oxygen-free environments are also conducted to verify the robustness of the regime map. This study provides mechanistic insights and a quantitative classification framework for topological transitions in laser-triggered liquid metal splashing.