Bubble and droplet motion in binary mixtures: Evaporation-condensation mechanism and Marangoni effect

TL;DR

This paper investigates bubble and droplet motion in binary mixtures driven by evaporation, condensation, and Marangoni effects, highlighting how concentration and temperature deviations influence the velocity fields.

Contribution

It provides a theoretical analysis of how Marangoni effects enhance bubble and droplet motion in binary mixtures, especially above a crossover concentration related to droplet size.

Findings

Marangoni effect significantly enhances velocity fields in binary mixtures.

Velocity enhancement depends on the crossover concentration inversely related to droplet radius.

Temperature and concentration deviations are quantitatively characterized.

Abstract

Bubble and droplet motion in binary mixtures is studied in weak heat and diffusion fluxes and in gravity by solving the linearized hydrodynamic equations supplemented with appropriate surface boundary conditions. Without gravity, the velocity field is induced by evaporation and condensation at the interface and by the Marangoni effect due to a surface tension gradient. In pure fluids, the latter nearly vanishes since the interface temperature tends to the coexistence temperature $T_{\rm cx}(p)$ even in heat flow. In binary mixtures, the velocity field can be much enhanced by the Marangoni effect above a crossover concentration $c^*$ inversely proportional to the radius $R$ of the bubble or droplet. Here $c^*$ is usually very small for large $R$ for non-azeotropic mixtures. The temperature and concentration deviations are also calculated.