Coarsening dynamics of condensing fluid thin films

Thin films of viscous fluids on hydrophobic surfaces are unstable and rapidly break up then slowly evolve as interacting localized droplets.

For mass-conserving dewetting dynamics, many aspects follow from results on phase separation in Cahn-Hilliard models from materials science.

Considered over long times, the volatility of the fluid will ultimately influence the state of the system. In a narrow range of conditions, the disjoining pressure can balance with thermal effects and care is needed to determine if evaporation or condensation will dominate. A lubrication PDE model was used to examine the long-time dynamics in a regime with weak condensation. A reduced-order dynamical system was derived for the interactions between quasi-steady droplets. Dynamics for arrays of identical drops and pairwise droplet interactions were investigated to provide insights into the coarsening dynamics of macroscopic systems. Weak condensation was shown to be a singular perturbation, fundamentally changing the long-time coarsening dynamics compared to non-volatile mass-preserving fluids. This was joint work with Hangjie Ji (NCSU).