Thermocapillary convection within short-duration pulse-heated liquid droplets

Thermocapillary-driven convection within short-duration pulse-heated liquid droplets was studied computationally. The phenomenon is governed By the di mensionless parameters of the surface-tension Reynolds number Re, the Prand tl number Pr, and the Riot number Ri. Critical surface-tension Re, Below wh ich the surface-temperature history is almost the same as the case of liqui d droplets experiencing pure heat diffusion (Re = 0) were determined. It wa s found that the effect of thermocapillary convection is more prominent for fluids with mid-Pr and for the conditions with finite-time-pulse duration. The results show that the critical Re is lower for mid-Pr fluids than for low-Pr fluids and thermocapillary convection is stronger for mid-Pr fluids. The finite-time-pulse duration also results in a lower critical Re. Transi ent streamline and temperature field contours are presented. The analysis o f thermocapillary flow was also performed for positive surface-tension temp erature coefficient fluids. It was shown that the resulting flow structure was totally different from that of negative surface-tension temperature coe fficient fluids.