Effect of groove sizes on the dynamic behavior of droplets impacting grooved cylindrical superhydrophobic surfaces

Abstract

Droplet impact on curved surfaces decorated with macroscopic structures is a common phenomenon in many industrial applications, yet the underlying mechanisms remain elusive. This study investigates the effects of groove width ratios (δ_w = D₀/w) and groove depth ratios (δ_h = D₀/h) through numerical simulations. The wettability transition thresholds, from the Cassie state to the Wenzel state, were determined within the range of δ_w from 6.15 to 24.6 and δ_h from 6.15 to 2.46, with the Weber number (We) varying from 3 to 30. It was found that a higher δ_w value correlates with a higher Weber number in the Wenzel state, while a higher δ_h value corresponds to a lower Weber number in the same state. Additionally, droplet spreading is influenced by both d_w and d_h, and the promotion or inhibition of droplet spreading becomes more pronounced as the Weber number increases. Through theoretical analysis, a prediction model for the relationship between the dimensionless axial maximum spreading diameter and the dimensionless azimuthal maximum spreading diameter was established. Furthermore, the relationship between contact time and Weber number was elucidated. These insights can provide valuable guidance for the design of superhydrophobic surface structures.