Characteristics and mechanism of droplet bouncing on cross-ridge superhydrophobic surfaces: Simulations and theory

Abstract

The behaviors of droplets impinging on superhydrophobic surfaces have received much attention from industry and academia due to potential applications such as anti-icing, spray cooling, and self-cleaning. Previous studies have shown that the superhydrophobic surfaces can significantly reduce contact time and thus effectively suppress surface icing and condensation phenomena. In this paper, the bouncing behaviors of droplets on superhydrophobic surfaces decorated with cross ridges were investigated using numerical simulations and theoretical analysis. The effect of cross-ridge structures with different pinch angles and droplets with different Weber numbers on droplet bouncing behaviors was investigated using the volume-of-fluid method. The results showed that the solid–liquid contact time was shortest when the angle between the two ridges was 75°. Compared to droplet bouncing on a smooth surface, the contact time was reduced by up to 30% for complete bouncing behaviors and up to 68% for broken bouncing behaviors. As the angle decreased, the ratio of spreading areas between child droplet sizes increased exponentially. The momentum of the smaller child droplet decreased until it was no longer generated. A theoretical analysis based on energy conservation was also performed. A theoretical equation was proposed to predict the maximum spreading coefficient. The maximum error was less than 10% for the experimental and numerical results compared to the predicted results.