Lattice Boltzmann study of evaporation phenomena

Thesis

Evaporation phenomena are having a resurgent interest in the recent years thanks to new techniques that allow for better flow visualization and microfabrication techniques of surfaces with interesting wetting properties. From the theoretical point of view the development of simulation techniques for evaporation phenomena is a challenging work due to the presence of moving interfaces and multiphase flows.

Thanks to its mesoscopic nature, the Lattice Boltzmann method is an ideal candidate for the simulation of evaporation phenomena. Here we present a Lattice Boltzmann algorithm capable to correctly reproduce the diffusion-limited evaporation dynamics.

We apply this numerical method to study the dynamics of multiple droplets evaporating together and we compare the results with experimental measures. We show that the presence of other droplets can dramatically increase the evaporation lifetime compared to the single droplet case; we also investigate the competition between convection and collective effects.

We then develop a theory to predict the instability behaviour of liquid fronts in two dimensional confined geometries and we consider the interplay between capillary forces, wettability gradients and phase changes. We use LB simulations to investigate the effect of a three dimensional geometry that cannot be taken into account in the analytical theory.

Finally we investigate the effect of flows on droplet evaporation. We consider both buoyancy induced and external flows. We show that even when diffusion is the dominant mechanism, flow effects are not negligible.

Authors: Laghezza, G

• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford