Instability patterns of Marangoni flow in evaporating droplets on lyophobic surface. (February 2023)

• Record Type: Journal Article
• Authors: Zhu, Ji-Long; Shi, Wan-Yuan
• Is Part Of: International communications in heat and mass transfer. Volume 141(2023)
• Publication Date: 2023-02
• Subjects: Marangoni flow patterns -- Longitudinal hydrothermal waves -- Droplet -- Evaporation -- Lyophobic surface; Heat -- Transmission -- Periodicals; Mass transfer -- Periodicals; Chaleur -- Transmission -- Périodiques; Transfert de masse -- Périodiques; Heat -- Transmission; Mass transfer; Periodicals; 621.4022
• DOI: 10.1016/j.icheatmasstransfer.2022.106598
• Languages: English
• ISSNs: 0735-1933

Abstract

Abstract: Although the evaporation flux distribution in droplets on lyophobic surface is quite different from that on lyophilic surface, the flow patterns of Marangoni convection in droplets on lyophobic surfaces is so far lack of understanding. In this paper, the instability patterns of Marangoni flow in droplet on heated lyophobic surface were numerically investigated via a three-dimensional model. Results found that the longitudinal hydrothermal waves and the oblique hydrothermal waves appeared sequentially in droplets with increasing Marangoni number and evaporative cooling number. Conversely, the oblique hydrothermal waves were generated for a small Pr, and transformed to the longitudinal hydrothermal waves as Pr increased. Nevertheless, a sufficiently large evaporative cooling number favored the incipience of the longitudinal hydrothermal waves with some small branches. The Bénard–Marangoni cells and longitudinal hydrothermal waves occurred in sequence under a low relative heat conductivity, while the longitudinal hydrothermal waves transformed to the oblique hydrothermal waves under a large relative heat conductivity. Highlights: Marangoni convection in sessile droplet evaporating on lyophobic surface was numerically simulated by 3D model. Longitudinal hydrothermal waves, oblique hydrothermal waves and Bénard–Marangoni cells were found. Wide ranges of Marangoni numbers, evaporative cooling numbers, heat conductivities and Prandtl numbers were considered.