Benard–Marangoni convection within isotropic droplets in overheated free standing smectic films

We study theoretically internal flows in isotropic droplets formed in horizontal free-standing smectic films (FSSF) overheated above the bulk smectic-isotropic transition. The convection is due to vertical temperature gradient in the film and is driven by the surface tension variations at the drop i...

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Bibliographic Details
Published in:	The European physical journal. E, Soft matter and biological physics Vol. 44; no. 6; p. 81
Main Authors:	Pikina, Elena S., Ostrovskii, Boris I., Pikin, Sergey A.
Format:	Journal Article
Language:	English
Published:	Berlin/Heidelberg Springer Berlin Heidelberg 01-06-2021 Springer Nature B.V
Subjects:	Biological and Medical Physics Biophysics Complex Fluids and Microfluidics Complex Systems Condensed matter physics Convection Convection cooling Droplets Hot Temperature Interface stability Internal flow Liquid Crystals - chemistry Marangoni convection Mathematical analysis Models, Chemical Nanotechnology Physics Physics and Astronomy Polymer Sciences Regular Article – Soft Matter Soft and Granular Matter Stability analysis Surface Tension Surfaces and Interfaces Temperature Temperature gradients Thermocapillary convection Thin Films
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Summary:	We study theoretically internal flows in isotropic droplets formed in horizontal free-standing smectic films (FSSF) overheated above the bulk smectic-isotropic transition. The convection is due to vertical temperature gradient in the film and is driven by the surface tension variations at the drop interfaces. Using a conventional linear instability theory, we have found analytically the conditions under which the mechanical equilibrium within isotropic droplets in FSSFs becomes unstable relative to the thermocapillary convection. An explicit expression for the Marangoni number characterizing the onset of the convection as a function of the wave vector of in-plane instability and parameters of heat transfer is obtained. The cellular instability in FSSF with isotropic droplets behaving as a normal fluid (surface tension is a decreasing function of temperature) is possible for both directions of thermal gradient across the film: from bottom to top and conversely. We propose possible experimental observations enabling to check our predictions. Graphicabstract
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	1292-8941 1292-895X 1292-895X
DOI:	10.1140/epje/s10189-021-00082-1