Some Insights into Drop Impacts on 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-dimensional parameters 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 different non-dimensionless parameters involved such as spreading factor, recoil height and the durations of several phases. The results indicate that the drop dynamics is determined by an interplay of drop inertia, viscosity and surface tension. Apart from Reynolds number and Weber number which are conventionally used to characterize drop impacts, a new non-dimensional impact parameter is introduced, and it is found out that the spreading factor and the different non-dimensional phase durations involved in the drop impact dynamics on a hydrophobic surface, scale fairly well with this newly defined impact parameter.