Some Insights into Drop Impacts on a Hydrophobic Surface

The current study reports the phenomenon of drop impacts on a hydrophobic surface in the substrate deposition regime (non-splashing), focusing on the characterization of each stage upon impact and different non-dimensional 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 (Re) and Weber number (We) which are conventionally used to characterize drop impacts, a new non-dimensional impact parameter, xi(= We(1/4) Re-1/5) 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. Further, systematic studies into the non-dimensional durations of each phase upon impact, spreading factor and recoil factor (i.e. non-dimensional recoil height) with respect to different non-dimensional parameters are reported.