Marangoni convection instabilities in an evaporating droplet on a non-isothermal substrate

The Marangoni convection instabilities are investigated in a sessile ethanol droplet as it evaporates on a non-isothermal substrate. The instability structures consistently, preferentially occur at the lower temperature side of substrate. Drifted by the azimuthal thermocapillary flow under externall...

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Bibliographic Details
Main Authors: Wang, Tian-Shi, Shi, Wan-Yuan, Duan, Fei
Other Authors: School of Mechanical and Aerospace Engineering
Format: Article
Language:English
Published: 2022
Subjects:
Online Access:https://hdl.handle.net/10356/161771
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Institution: Nanyang Technological University
Language: English
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Summary:The Marangoni convection instabilities are investigated in a sessile ethanol droplet as it evaporates on a non-isothermal substrate. The instability structures consistently, preferentially occur at the lower temperature side of substrate. Drifted by the azimuthal thermocapillary flow under externally imposed temperature gradient, the longitudinal rolls are found to propagate from the hot side to the cold side for the droplet, while a radial propagation of the BM cells directly from the cold side to the hot side along the droplet diameter occurs at the last period of evaporation process. The azimuthal propagation speed of longitudinal rolls increases with the increase of temperature gradient, but is independent of the mean temperature of the substrate. Effects of the mean temperature of substrate and the temperature gradient on the Marangoni instabilities are investigated, and the critical conditions for the onset of longitudinal rolls are determined.