Effects of surface tension and viscosity on the impact process of droplets onto a rotational surface

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 degrees after impact, and the number of secondary droplets were proposed.