The droplet dynamics of asymmetrical impingement on moving ridged surface

The depth of research into the mechanism of droplet impacting structured surfaces dictates the efficacy of their applications. The impact stress generated when a droplet impacts a surface is a pivotal factor influencing the efficiency of surface applications, ultimately determining the extent of surface wear. Despite the systematic examination of impact force, there remains a scarcity of research on impact stress and its mitigation strategies. Consequently, the objective of this study is to delve into the mechanisms that reduce maximum impact stress following the introduction of aerodynamic boundary layer and structural design.

Based on experimental investigations, we examined the dynamic behavior of droplet impacting moving ridged surface with varying offset ratios across different tangential and normal Weber numbers. This study emphasizes the impact behavior phase diagram, droplet spreading length, and other relevant parameters. Furthermore, we systematically analyzed the evolution of the flow field and surface stress during the impact process benefit from a numerical simulation of a two-phase laminar flow model.

This study shows that the impact of droplets on moving ridged surfaces significantly influences stress reduction, with a focus on asymmetric droplet impacts. The research establishes a phase diagram for droplet impact behaviors across varying tangential Weber number (We_τ), normal Weber number (We_n) and offset ratio (χ), and some unified models about the maximum spreading diameter (D_max) of the droplet are obtained based on the above variables. Besides, a model based on Prandtl's boundary layer theory emphasizes and proves the positive effect of the introduction of air layer on the reduction of maximum impact stress. Notably, the offset ratio significantly influences stress distribution, the maximum impact stress shows a non-monotonic change from increasing first to decreasing as χ increases considering the rotation of droplet. This research contributes valuable insights into surface design strategy for enhancing the resistance to droplet impact wear. These findings have broad implications for industrial applications where managing droplet impingement is crucial.