Non-wetting drop dynamics

TL;DR

This study investigates droplet impact dynamics on non-wetting surfaces through experiments and a simplified model, revealing key dimensionless parameters that govern the behavior and providing insights into non-wetting droplet impacts.

Contribution

The paper introduces a minimal model identifying two main non-dimensional groups that describe non-wetting droplet impact dynamics, supported by experimental validation.

Findings

Droplet dynamics are governed by two key non-dimensional parameters.

The model accurately predicts impact behavior for moderate Ohnesorge numbers.

Discrepancies exist for very small Ohnesorge numbers, indicating areas for further research.

Abstract

The impact of droplets on solids or weakly-deformable surfaces can lead to non-wetting outcomes, depending on the control parameters. Here, we perform experiments and develop a simple model to understand the impact dynamics by varying three important drop parameters: the Ohnesorge number $\mathcal{O}h$, the Bond number $\mathcal{B}o$ and the Weber number $\mathcal{W}e$. The model suggests that the droplet dynamics is captured by only two non-dimensional groups, namely $\ \mathcal{O}h$ and $\xi = \mathcal{B}o/\sqrt{\mathcal{W}e}$. For $\xi \ll 1$, the droplet dynamics is fully dominated by $\mathcal{O}h$, but for $\xi \gg 1$, the dynamics depends both on $\mathcal{O}h$ and $\xi$. While the model results show some discrepancies for small $\mathcal{O}h$, they are in very good agreement with the experiments for moderately large $\mathcal{O}h$. The work thereby offers an elaborate description of the droplet impact dynamics in a non-wetting scenario.