The multicomponent diffuse-interface model and its application to water/air interfaces

TL;DR

This paper develops and applies a multicomponent diffuse-interface model to study water-air interfaces, revealing stability conditions, phase transition behaviors, and the influence of external parameters on interfacial dynamics.

Contribution

It introduces a comprehensive multicomponent DIM framework and applies it specifically to water-air systems, analyzing interfacial stability, phase transitions, and parameter determination.

Findings

Flat interfaces with monotonic densities are stable.

Vapor contact with liquid leads to evaporation or expansion.

Spontaneous condensation occurs with large contact angles.

Abstract

Fundamental properties of the multicomponent diffuse-interface model (DIM), such as the maximum entropy principle and conservation laws, are used to explore the basic interfacial dynamics and phase transitions in fluids. Flat interfaces with monotonically-changing densities of the components are proved to be stable. A liquid layer in contact with oversaturated but stable vapour is shown to either fully evaporate or eternally expand (depending on the initial perturbation), whereas a liquid in contact with saturated vapour always evaporates. If vapour is bounded by a solid wall with a sufficiently large contact angle, spontaneous condensation occurs in the vapour. The external parameters of the multicomponent DIM -- e.g., the Korteweg matrix describing the long-range intermolecular forces -- are determined for the water-air combination. The Soret and Dufour effects are shown to be negligible in this case, and the interfacial flow, close to isothermal.