Moving contact lines in a pure-vapor atmosphere: a singularity-free description in the sole framework of classical physics

TL;DR

This paper demonstrates that in a pure vapor environment, moving contact lines do not produce singularities within classical physics, challenging previous assumptions about the necessity of microscopic effects for regularization.

Contribution

It provides a singularity-free classical physics description of moving contact lines in pure vapor atmospheres without relying on microscopic regularization mechanisms.

Findings

No singularities arise in pure vapor conditions.

Evaporation does not introduce singularities even with superheated substrates.

Classical physics suffices to describe contact line motion in these conditions.

Abstract

We here show that, even in the absence of "regularizing" microscopic effects (viz. slip at the wall or the disjoining pressure/precursor films), no singularities in fact arise for a moving contact line surrounded by the pure vapor of the liquid considered. There are no evaporation-related singularities either even should the substrate be superheated. We consider, within the lubrication approximation and a classical one-sided model, a contact line advancing/receding at a constant velocity, or immobile, and starting abruptly at a (formally) bare solid surface with a zero or finite contact angle.