Reversed role of liquid viscosity on drop splash

The influence of liquid viscosity on the splashing behavior of a drop impacting a smooth surface is investigated. It is found that the liquid viscosity plays a reversed role on the drop splash, and the liquid viscosity promotes the drop splash in the low-viscosity cases but suppresses the drop splash in the high-viscosity cases. Here, we focus on the dynamics of the lifting lamella during the splashing behavior and demonstrate that the increase in liquid viscosity could contribute to the lower splashing angle αs. Furthermore, an empirical relationship of the splashing angle is obtained according to the experimental results. The reversed role of liquid viscosity is reflected in the positive effect both on the aerodynamic force and viscous force. For low-Oh cases, the increase in aerodynamic force predominates and promotes the drop splash. For high-Oh cases, the increase in viscous force predominates and suppresses the drop splash. We eventually put forward a splash criterion on smooth surfaces, which could successfully characterize the splashing behavior in this work and previous studies, and indicate the reversed role of liquid viscosity on drop splash.