  Surface-tension-dominant droplet evaporation is ubiquitous and of importance
to many applications. We present an improved Coupled Level Set and Volume of
Fluid (i-CLSVoF) framework without explicit interface reconstruction for
modelling micro-sized droplets with and without evaporation. In the i-CLSVoF
framework, an improved surface tension force model with additional filtering
steps to filter un-physical spurious velocities is developed and implemented. A
simple, yet efficient, velocity-potential based approach is proposed to
reconstruct a divergence-free velocity field for the advection of the free
surface during droplet evaporation. This approach fixes the numerical issues
resulting from the evaporation-induced velocity jump at the interface. The
smeared mass source term approach incorporated in this work guarantees greater
numerical stability than the non-smeared approach. Three different evaporation
models (constant mass flux, thermally driven evaporation and droplet
evaporation at room temperature) are implemented in the i-CLSVoF. Corresponding
numerical benchmark cases (dam break, droplet relaxation and droplet
evaporation subjected to different evaporation models) are conducted to
validate the surface tension and the evaporation models. Good agreement between
the numerical and corresponding analytical solutions is found. The model
developed in this work shows convincing performance in modelling
surface-tension-dominant flow with and without evaporation.
