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In the present study, the impact process of droplets onto a rotational surface was experimentally studied. The influences of the rotational speed, liquid surface tension, and viscosity on the impact phenomena were carefully investigated. The phenomena of asymmetric spreading, splashing with and without liquid filament, finger formation, and secondary droplets were observed. The results showed that, at the same rotational speed, decrease in the surface tension could result in increase in the wetting length in angular direction and the wetting area. In addition, the splashing threshold was discussed based on the analysis of the lift force. In addition, increase in the linear velocity of the surface could promote the splashing behavior and generate more fingers and secondary droplets. Moreover, droplets with higher viscosity could produce more secondary droplets and less fingers. Meanwhile, droplets with higher surface tension could produce more fingers and less secondary droplets. In addition, new correlations for the spreading ratio, the number of fingers formed at the angle of 150° after impact, and the number of secondary droplets were proposed. [ABSTRACT FROM AUTHOR]

A droplet impinging on a liquid film finds numerous applications in diverse scientific fields. Although studies have primarily focused on spherical droplets, a droplet can present both spherical shape and non-spherical shape at the moment of impact. In the present study, the impact dynamics of a non-spherical droplet on a thin liquid film is investigated experimentally. The results show that, under the same film thickness and Weber number conditions, the splashing and deposition regimes are different for different droplet shapes such as prolate, sphere, and oblate. It is found that the splashing threshold (Ksp) is changed according to the shape of the droplet. Under the same condition when a spherical droplet is in the deposition mode, an oblate droplet is more likely to splash and form secondary droplets, while a prolate droplet is more splash-resistant even at higher Weber numbers. A modified theoretical model for crown radius evolution is developed. The predictions of theoretical model are found to agree well with the experimental results for spherical and non-spherical droplets. Moreover, at the same Weber number, a prolate droplet has a relatively higher maximum crown height than those of an oblate droplet and a spherical droplet. [ABSTRACT FROM AUTHOR]