Journal
INTERNATIONAL JOURNAL OF THERMAL SCIENCES
Volume 117, Issue -, Pages 274-286Publisher
ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER
DOI: 10.1016/j.ijthermalsci.2017.04.007
Keywords
Sessile droplet; Benard-Marangoni convection; Thermocapillary convection; Instability
Categories
Funding
- National Natural Science Foundation of China [51676018, 51176210]
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In order to investigate Marangoni convection in a sessile droplet on heated substrate, a series of threedimensional numerical simulations are carried out in a wide range of Marangoni number. A low volatile silicone oil is adopted and the effect of evaporation is neglected. Benard-Marangoni convection and thermocapillary convection may coexist in droplet because of its curve surface. When Marangoni number is low the flow is steady axisymmetric thermocapillary convection whereas the flow becomes to be asymmetric and loses its stability and Hopf bifurcation occurs when Marangoni number high. The oscillatory transition convection, steady Benard-Marangoni convection and irregular oscillatory Benard-Marangoni convection appear in sequence with increasing Marangoni number. The characteristics of each kind of convection modes are described and the critical Marangoni numbers for the incipience of them are determined in a wide range of contact angles. One of the most interesting phenomenon is that the shape of the Benard-Marangoni convection cell in sessile droplet is circular, which is different from that of classical hexagonal cell in flat layer. With increasing contact angle, the critical Marangoni number for the onset of convection instabilities first decreases and then increases. Critical cell number of the steady Benard-Marangoni convection keeps on only one for contact angle less than 15 whereas it increases sharply after angle lager than 15 degrees. The numerical results are qualitatively verified by experiment. (C) 2017 Elsevier Masson SAS. All rights reserved.
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