Observation of the pressure effect in simulations of droplets splashing on a dry surface

TL;DR

This study uses high-resolution simulations to investigate how ambient pressure influences droplet splashing on dry surfaces, comparing multiple theoretical models to experimental observations.

Contribution

It provides the first detailed numerical comparison of various models explaining the pressure effect in droplet splashing phenomena.

Findings

Gas film under droplet predicted by skating droplet model

Lamella ejection velocity scaling matches impact velocity

Lift force hypothesis aligns with simulation results

Abstract

At atmospheric pressure, a drop of ethanol impacting on a solid surface produces a splash. Reducing the ambient pressure below its atmospheric value suppresses this splash. The origin of this so-called pressure effect is not well understood and this is the first study to present an in-depth comparison between various theoretical models that aim to predict splashing and simulations. In this work the pressure effect is explored numerically by resolving the Navier-Stokes equations at a 3-nm resolution. In addition to reproducing numerous experimental observations, it is found that different models all provide elements of what is observed in the simulations. The skating droplet model correctly predicts the existence and scaling of a gas film under the droplet, the lamella formation theory is able to correctly predict the scaling of the lamella ejection velocity as function of the impact velocity for liquids with different viscosity, and lastly, the dewetting theory's hypothesis of a lift force acting on the liquid sheet after ejection is consistent with our results.