Drop impact on viscous liquid films

Abstract

When a liquid drop falls on a solid substrate, the air layer in between them delays the occurrence of liquid--solid contact. For impacts on smooth substrates, the air film can even prevent wetting, allowing the drop to bounce off with dynamics identical to that observed for impacts on superamphiphobic materials. In this article, we investigate similar bouncing phenomena, occurring on viscous liquid films, that mimic atomically smooth substrates, with the goal to probe their effective repellency. We elucidate the mechanisms associated to the bouncing to non-bouncing (floating) transition using experiments, simulations, and a minimal model that predicts the main characteristics of drop impact, the contact time, and the coefficient of restitution. In the case of highly viscous or very thin films, the impact dynamics is not affected by the presence of the viscous film. Within this substrate--independent limit, bouncing is suppressed once the drop viscosity exceeds a critical value as on superamphiphobic substrates. For thicker or less viscous films, both the drop and film properties influence the rebound dynamics and conspire to inhibit bouncing above a critical film thickness. This substrate--dependent regime also admits a limit, for low viscosity drops, in which the film properties alone determine the limits of repellency.

arXiv commentPlease find the supplemental videos here: https://youtube.com/playlist?list=PLf5C5HCrvhLHJXLqwpylEwYc2rVtTsCUX

References in corpus (20)

• Drop impact on superheated surfaces
• On the spreading of impacting drops
• Water spring: a model for bouncing drops
• Dynamic Leidenfrost effect: relevant time- and length-scales
• Direct measurements of air layer profiles under impacting droplets using high-speed color interferometry
• Impact forces of water drops falling on superhydrophobic surfaces
• Spray formation: a numerical closeup
• Droplet impact on a thin liquid film: anatomy of the splash
• Self-propulsion of inverse Leidenfrost drops on a cryogenic bath
• Lifting a sessile oil drop from a superamphiphobic surface with an impacting one
• Three-dimensional dynamics of a pair of deformable bubbles rising initially in line. Part 1: Moderately inertial regimes
• When does an impacting drop stop bouncing?
• The role of the droplet deformations in the bouncing droplet dynamics
• Drop impact on viscous liquid films
• The Leidenfrost effect as a directed percolation phase transition
• Drop Trampoline
• Deformation and relaxation of viscous thin films under bouncing drops
• Levitation of non-magnetizable droplet inside ferrofluid
• Capillary-scale solid rebounds: experiments, modelling and simulations
• Dimple drainage before the coalescence of a droplet deposited on a smooth substrate

Cited by in corpus (9)

• Unifying theory of scaling in drop impact: Forces & maximum spreading diameter
• When does an impacting drop stop bouncing?
• Drop impact on viscous liquid films
• Inertio-capillary rebound of a droplet impacting a fluid bath
• The role of viscosity on drop impact forces on non-wetting surfaces
• Drop rebound at low Weber number
• Birth of a bubble: Drop impact onto a thin liquid film for an immiscible three-fluid system
• Spinning Twisted Ribbons: When Two Holes Meet on a Curved Liquid Film
• Droplet rebounds off a fluid bath at low Weber numbers