Splashing characteristics and dynamics of drops impingement on ultracold surfaces

Abstract

Drop impingement on low-temperature surfaces is a common phenomenon in various situations, such as the icing process on airplanes and spray impingement in internal combustion engines in an ultracold environment. Numerous literatures have reported the spreading and icing characteristics during the cold surface impingement but the characteristics and dynamics of the splashing process under a similar circumstance have not been comprehensively investigated. In this work, the drop splashing process on low-temperature surfaces is investigated both experimentally and theoretically. By employing high-speed shadowgraphy, we find the drop splashing pattern gradually changes from prompt splash to corona splash as the surface temperature decreases from 20 °C to −39 °C because of the physical property changes of the liquid in the drop. The splashing threshold decreases monotonically with surface temperature. The critical Weber number to trigger splash decreases from 441 to 235 and 288 respectively on aluminium and PMMA surfaces as surface temperature drops from 20 °C to −30 °C. A semi-theoretical model to predict the splashing threshold is established based on Riboux and Gordillo’s theory, while the suction force is found dominating the lift forces that induce the levitation of the liquid film. Temperature characteristics of the surrounding air and drop are simplified based on a simulation analysis. The model shows fair agreement with the experiments on both aluminium and PMMA surface.