Spreading and Recoil of Drops Impacting a Hydrophobic Surface

Abstract

Drop impacts on liquid and solid surfaces have been widely studied for reasons that are relevant both in nature and in industry. Although a slew of prior research has been reported on the different aspects of drop impacts on a solid surface, systematic studies into the durations of each phase upon impact, spreading distance and recoil height with respect to different liquid properties and across a wide range of non-dimensionless numbers are difficult to find. The current study reports the phenomenon of drop impacts in the substrate deposition regime (non-splashing), focusing on the characterization of each stage upon impact and its variation of different non-dimensionless parameters. The results indicate that the drop dynamics is determined by an interplay of drop inertia, viscosity and surface tension. Although Reynolds number and Weber number are conventionally used to characterize drop impacts, a new non-dimensional impact parameter (that is a function of Re and We) is introduced, and it is found out that spreading factor and the different non-dimensional phase durations involved in the drop dynamics scale well with this impact parameter.

Keywords: Drop Impact; Maximum Spreading; Drop Recoil; Impact Parameter; Weber Number