We studied fluid flows in evaporating sessile ethanol droplets subjected to heating by CW laser radiation via the light-absorbing substrate. The flow dynamics under the combined effect of evaporative cooling and localized laser heating were investigated using a fully coupled nonisothermal flow finite element model incorporating the arbitrary Lagrangian–Eulerian moving mesh methodology to accurately capture the motion of the droplet surface due to evaporation in the constant contact angle mode. The competition between Marangoni flows driven by these two thermal mechanisms and the resulting control over the flow pattern, average temperature and droplet evaporation time is elucidated. It is shown that flow switching to the laser-induced circulation pattern is characterized by flow velocities more than an order of magnitude faster than the pre-laser state. This flow reorganization significantly increased the droplet’s average temperature and drastically reduced the total evaporation time. The findings of the study provide new foundations for active control of droplet dynamics in microfluidic and coating technologies.
A. V. Dyshlyuk (Mon,) studied this question.