Post collision hydrodynamics of droplets on cylindrical bodies of variant convexity and wettability

TL;DR

This study experimentally investigates the post-impact behavior of water droplets on convex cylindrical surfaces with varying wettability and convexity, analyzing how impact parameters influence spreading and film dynamics.

Contribution

It introduces new experimental insights and theoretical models for droplet impact dynamics on cylindrical surfaces with different wettability and convexity.

Findings

Wetting fraction and spread factor increase with impact Weber number and decrease with diameter ratio.

Spread factor is independent of target wettability.

Theoretical models accurately predict maximum wetting fraction and film thickness evolution.

Abstract

Post impingement morphology and dynamics of water droplets on convex cylindrical surfaces has been explored experimentally. Droplet impact and post-impact feature studies have been conducted on hydrophillic and superhydrophobic cylindrical surfaces. Effects of the impact Weber number and target-to-drop diameter ratio have been studied. The post-impact hydrodynamics have been quantified using the wetting fraction, the spreading factor and nondimensional film thickness at the north pole of the target. The observations reveal that the wetting fraction and spread factor increases with an increase in the impact We and decrease in the target to drop diameter ratio. An opposite trend is noted for nondimensional film thickness at the targets north pole. It is also deduced that the spread factor is independent of the target wettability. The lamella dynamics post spreading has also been observed to be a strong function of the wettability, impact We and the diameter ratio. An analytical expression for temporal evolution of film thickness at north pole of the cylinderical target is derieved. Another theoretical model based on energy conservation for predicting the maximum wetting fraction for variant cylindrical targets in terms of the governing We and Capillary number and the experimental measurements are in good agreement with the theoretical predictions.