Marangoni convection-driven laser fountains on free surfaces of liquids

• DOI: 10.1016/j.mtphys.2021.100558
• Publication Date: 2021-10-27T13:00:09Z
• Authors: Feng Lin; Aamir Nasir Quraishy; Tian Tong; Runjia Li; Guang Yang; Mohammadjavad Moh...; Yi Qiu; Talari Vishal; Junyi Zhao; Wei Zhang; Hong Zhong; Hang Zhang; Zhongchen Chen; Chaofu Zhou; Xin Tong; Peng Yu; Jonathan Hu; Suchuan Dong; Dong Liu; Zhiming Wang; John R. Schaibley; Jiming Bao
• Keywords: Free surface; Fountain

Abstract It is well known that an outward Marangoni convection from a low surface tension region will make the free surface of a liquid depressed. Here, we report that this established perception is only valid for thin liquid films. Using surface laser heating, we show that in deep liquids a laser beam pulls up the fluid above the free surface generating fountains with different shapes, and with decreasing liquid depth a transition from fountain to indentation with fountain-in-indentation is observed. High-speed imaging captures a transient surface depression before steady elevation is formed, and computational fluid dynamics simulations reveal the underlying flow patterns and quantify the depth-dependent and time-resolved surface deformations. Systematic investigation of the effect of laser parameters, surface tension and area of the fluid on its surface deformation further confirms that the laser fountain is a result of dynamic competition between outgoing Marangoni convection and the upward recirculation flow. Experiments and simulations also reveal that a smaller surface area can dramatically strengthen laser fountain. The discovery of laser fountain and the development of related experimental and simulation techniques have upended a century–old perception and opened up a new regime of interdisciplinary research and applications of Marangoni-induced interface phenomena.