Effect of the grooved structure on dynamic behavior of droplets impinging on the cylindrical superhydrophobic surface

The dynamic behavior of droplets impacting a grooved cylindrical superhydrophobic surface (a circular cylindrical shape with groove) was studied via experiments performed over D* (defined as the ratio of cylinder diameter D to initial droplet diameter D0) ranging from 4 to 9 and We ranging from 3 to 210. Parameters including the spreading, receding, splashing, and contact time were investigated. Five possible behaviors of the droplets, including complete rebound, partial rebound, no rebound, stretched breakup rebound and stretched breakup, were observed on the grooved cylindrical superhydrophobic surface. Based on the Weber number, the sites of these phenomena into three regions, namely complete rebound region (complete rebound), transition region (partial rebound, non-rebound), and splash region (stretched breakup rebound and stretched breakup) were divided. The results revealed that the diameter ratio D*, We, and grooved structure have a significant effect on the droplet morphology. The grooved structure hindered the droplet spreading and splashing in the perpendicular direction of the droplet and promoted the droplet spreading and splashing in the parallel direction. In addition, an equation for predicting the maximum axial and azimuthal spread diameter was proposed. Compared with the cylindrical surface, the grooved cylindrical surface could reduce the contact time of droplets within a certain range of We.