Effect of Ambient Pressure and Impact Angle on Splashing Threshold during Droplet Impact

While the threshold of splashing when liquid droplets impact against rigid solid surfaces is known to be related to the Weber number (We), the effect of ambient gas pressure (or density) and the impact angle have not been systematically studied. In this study, we examine the effects of droplet velocity, impact angle, and ambient gas pressure (or density) on the threshold of splashing. In our methodology, a FC-72 droplet of 1.7 mm in diameter is used, and the droplet velocity, impact angle, and ambient pressure are varied systematically. Then a semi-empirical and analytical correlation is developed based on experimental results. This correlation demonstrates that when the internal droplet pressure, which is caused by the change of momentum of the droplet during the impact process, is larger than the stress due to the surface tension, splashing occurs. Also, this correlation considers the reduction in the splashing as the droplet impact angle increases. ψ Corresponding author: [email protected]