Hydrothermal waves in evaporating annular pools and sessile drops using DNS

Thermocapillary effects generated due to thermal gradients in annular liquid pools and resulting in hydrothermal waves under inert, saturated and evaporating atmospheres are investigated using two-phase direct numerical simulations in 3D. For annular pools under inert environments, the volume-of-fluid method is used to capture the interface, with special attention towards the grid resolution near the vapour-liquid interface. The results show that the interface temperature distribution follows a regular azimuthal pattern, representative of hydrothermal wave structures, along with small-amplitude interfacial waves. The effects of evaporation fluxes and the interfacial depths on the linear (early-time) and non-linear (late-time) development of hydrothermal temperature and interfacial waves will be presented. Under inert environments, the azimuthal structures qualitatively agree with experimental and numerical studies (with a single-phase model and a non-deformable free surface) of Schwabe et. al. (2003). Evaporating sessile droplets simulated using diffuse-interface method will be presented and compared against analytical integral balance models.