Owing to the poor wettability of liquid metals, it is difficult to form a continuous film on solid substrates under non-oxidized conditions. To overcome this limitation, our previous study proposed a novel pre-filled microstructured substrate (PFMS), which enables liquid metals to achieve complete spreading on its surface Wang et al., “Experimental investigation of a novel liquid metal plasma facing component with pre-filled microstructures,” arXiv:2505.08512 (2025). Based on this substrate, the present study experimentally investigates the impact of liquid metal droplets on thin metal films of different thicknesses (dimensionless film thickness h* = 0.33–1.67) under non-oxidized conditions, with Weber number (We) ranging from 5.5 to 218. The film thickness in experiments is less than 6 mm. The impact dynamics were recorded using a high-speed camera, and five typical impact phenomena were observed: total coalescence, prompt splashing, central jetting, the formation of a single satellite droplet, and multiple satellite droplets. The results show that prompt splashing is more likely to occur on thinner liquid films. The dimensionless crown radius scales linearly with the dimensionless evolution time, and its slope K exhibits a scaling relationship with We−1/4. The experiments also revealed a transition between two distinct central jet morphologies: thick jet and thin jet. In contrast, no such transition was observed in the comparison experiments of water droplets. The analysis indicates that the presence of the PFMS, together with the high surface tension and density of the liquid metal, contributes to the multiple transitions of the central jet morphology. The new findings may provide potential values for the development of liquid–solid composite divertors in nuclear fusion reactors.
Chen et al. (Thu,) studied this question.