Transition time of a bouncing drop

TL;DR

This paper investigates the transition time during a water drop's impact on superhydrophobic surfaces, revealing it is Weber number-independent and constitutes half of the contact time, with implications for understanding drop dynamics.

Contribution

It introduces the concept of transition time in drop impact dynamics and demonstrates its Weber number independence through experiments and simulations.

Findings

Transition time is Weber number-independent.

Transition time accounts for half of the contact time.

Lamella contains 1/4 of the total drop volume at maximum spreading.

Abstract

Contact time of bouncing drops is one of the most essential parameters to quantify the water-repellency of surfaces. Generally, the contact time on superhydrophobic surfaces is known to be Weber number-independent. Here, we probe an additional characteristic time, \emph{transition time} inherent in water drop impacting on superhydrophobic surfaces, marking a switch from a predominantly lateral to an axial motion. Systematic experiments and numerical simulations show that the transition time is also Weber number-independent and accounts for half the contact time. Additionally we identify a Weber-independent partition of volume at the maximum spreading state between the rim and lamella and show that the latter contains 1/4 of the total volume of the drop.