Simulation on the Marangoni flow and heat transfer in a laser-heated suspended droplet

Abstract

In this study, the Marangoni flow and heat transfer inside a laser-heated water droplet suspended in the immiscible oil phase is numerically investigated. It is shown that the Marangoni flow is induced by non-uniform temperature distribution across the droplet interface caused by the localized heating source. Effects of the laser power, laser beam size and surface tension temperature coefficient are investigated. Simulation results show that the temperature rising rate and average temperature rising linearly increase with laser power due to more heat generated by photothermal effect and the Marangoni flow is intensified due to larger interface temperature gradient. With increasing laser beam diameter, the temperature distribution becomes more uniform due to more uniform laser energy distribution. The Marangoni flow is reverse when the surface tension temperature coefficient changes from the positive to the negative and vice versa, resulting in the transformation of the Marangoni flow and temperature distribution.