On the evaporation dynamics of Ouzo ternary mixture droplets

The evaporation of ternary mixed droplets (TMDs) is a complex multi-physical process involving the evaporation of different components, interactions, and surface phenomena. Understanding and simulating such a process is of great importance for many industrial applications and scientific research. In this study, a theoretical model for the evaporation dynamics of TMDs is developed, and the finite element method is used to simulate the dynamic evaporation of Ouzo TMDs on a heated substrate. The internal flow structure during the evaporation is analyzed, and the unique, spontaneous emulsification phenomenon, known as the “Ouzo effect,” is explored. The influence of substrate heating temperature and initial ethanol concentration on the evaporation characteristics of Ouzo TMDs is also examined. The results show that in the early stages of evaporation, the droplets exhibit a chaotic multi-vortex flow structure. As evaporation progresses, the internal flow becomes predominantly clockwise, while in the later stages, the flow direction reverses to counterclockwise. The highest liquid temperature is observed at the contact line, where ethanol evaporates more rapidly. The Ouzo effect first appears near the contact line and gradually spreads along the bottom of the droplet toward the interior, ultimately reaching the center. Both increasing the substrate heating temperature and the initial ethanol concentration accelerate the evaporation rate of the droplets. Higher substrate heating temperature not only accelerates both the evaporation and emulsification processes but also shortens the duration of the Ouzo effect. In contrast, a higher initial ethanol concentration delays the onset of the Ouzo effect and reduces its duration.