Drops bouncing off macro-textured superhydrophobic surfaces

TL;DR

This study uses advanced 3D simulations to explore how macro-textured superhydrophobic surfaces influence droplet bouncing, revealing new regimes, effects of texture density, and energy dynamics that extend understanding beyond current experiments.

Contribution

It introduces the first 3D simulations of droplet impact on macro-textured surfaces, providing detailed insights into the physics and energy interactions involved.

Findings

Reduction of contact time extends to higher Weber numbers.

Texture density significantly influences bouncing behavior.

Energy analysis reveals the interplay between kinetic, surface energy, and dissipation.

Abstract

Recent experiments with droplets impacting a macro-textured superhydrophobic surfaces revealed new regimes of bouncing with a remarkable reduction of the contact time. We present here a comprehensive numerical study that reveals the physics behind these new bouncing regimes and quantify the role played by various external and internal forces that effect the dynamics of a drop impacting a complex surface. For the first time, three-dimensional simulations involving macro-textured surfaces are performed. Aside from demonstrating that simulations reproduce experiments in a quantitative manner, the study is focused on analyzing the flow situations beyond current experiments. We show that the experimentally observed reduction of contact time extends to higher Weber numbers, and analyze the role played by the texture density. Moreover, we report a non-linear behavior of the contact time with the increase of the Weber number for application relevant imperfectly coated textures, and also study the impact on tilted surfaces in a wide range of Weber numbers. Finally, we present novel energy analysis techniques that elaborate and quantify the interplay between the kinetic and surface energy, and the role played by the dissipation for various Weber numbers.