Droplet Impact Dynamics On Randomly Rough Surfaces: A Computational Study

Tremendous efforts have been devoted to the modeling of droplet deposition on smooth and patterned surfaces with ordered structures. However, systematic work focusing on randomly rough surfaces, which are the most common bare substrate surfaces, can hardly be identified. The quantitative relationships derived from this study can eventually shed light on droplet shape on-aim control during the deposition process, which is of great practical importance in many applications.A fluid mechanics phase field modeling method together with a unique analysis approach has been developed in this work to characterize single droplet deposition on randomly rough surfaces. It is interesting to observe that the droplet shape evolves quite differently on a randomly rough surface, as compared to a patterned surface, even if two surfaces have the same roughness.Parametric studies have been carried out to explore how the morphological metrics of randomly rough surfaces, which include the conventional Wenzel roughness parameter(Wr) and the newly proposed relative roughness parameter( Rr), can affect droplet impact dynamics. Analyses of the initial conditions of the droplet impact on the maximum spreading diameter, also summarizes the semi-empirical formula of maximum spreading diameter.