Multicellular structures in thin free liquid films induced by thermocapillary effect

Takahiro Homma; Tokiya Yamashita; Ryohei Wada; Koki Kawazu; Kizuku Kurose; Takahiro Tsukahara; Ichiro Ueno

doi:10.1016/j.jcis.2023.02.151

Multicellular structures in thin free liquid films induced by thermocapillary effect

J Colloid Interface Sci. 2023 Jul:641:187-196. doi: 10.1016/j.jcis.2023.02.151. Epub 2023 Mar 9.

Authors

Takahiro Homma¹, Tokiya Yamashita², Ryohei Wada³, Koki Kawazu⁴, Kizuku Kurose⁵, Takahiro Tsukahara⁶, Ichiro Ueno⁷

Affiliations

¹ Division of Mechanical Engineering, Graduate School of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, 278-8510, Chiba, Japan. Electronic address: 7520567@alumni.tus.ac.jp.
² Division of Mechanical Engineering, Graduate School of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, 278-8510, Chiba, Japan. Electronic address: 7522572@ed.tus.ac.jp.
³ Division of Mechanical Engineering, Graduate School of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, 278-8510, Chiba, Japan. Electronic address: 7518569@alumni.tus.ac.jp.
⁴ Division of Mechanical Engineering, Graduate School of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, 278-8510, Chiba, Japan. Electronic address: 7520523@alumni.tus.ac.jp.
⁵ Department of Mechanical Engineering (Department of Mechanical and Aerospace Engineering after Apr. 2023), Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, 278-8510, Chiba, Japan. Electronic address: kurose@rs.tus.ac.jp.
⁶ Department of Mechanical Engineering (Department of Mechanical and Aerospace Engineering after Apr. 2023), Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, 278-8510, Chiba, Japan. Electronic address: tsuka@rs.tus.ac.jp.
⁷ Department of Mechanical Engineering (Department of Mechanical and Aerospace Engineering after Apr. 2023), Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, 278-8510, Chiba, Japan. Electronic address: ich@rs.tus.ac.jp.

PMID: 36934574
DOI: 10.1016/j.jcis.2023.02.151

Abstract

Hypothesis: Multicellular convective structures that are induced in a fluid exposed to temperature difference are commonly observed in nature and in daily life. Different types of basic flow patterns are induced in a free liquid film by thermocapillary effect, whereas the formation of such multicellular structures has not been hitherto unravelled.

Experiments: A thin film of high-Prandtl-number liquid is prepared in a rectangular aperture of the order of 0.1 mm in thickness sustained by its surface tension. A designated temperature difference is imposed between the end surfaces of the aperture to generate a thermocapillary-driven convection in the free liquid film. We monitor the induced thermal flow patterns to evaluate the cell numbers and their wavelength by experimental and numerical approaches.

Findings: The multicellular structure is established by the thermocapillary effect in the free liquid films. The cell number increases in a stepwise manner as the liquid-film width increases. When the cell number increases, another pair of the cells always newly emerges. We determine the wavelength in a non-dimensional manner, and present the variation of the wavelength against the aspect ratio corresponding to the liquid-film width. The results are compared to those of convectional Marangoni-Bénard convection.

Keywords: Cell length; Free liquid film; Multicellular structure; Thermocapillary effect; Wavenumber.