Marangoni convection in evaporating meniscus with changing contact angle

Marangoni convection in evaporating meniscus with changing contact angle In this work, the Marangoni convection in the liquid phase of an evaporating meniscus interface in open air has been studied for varying contact angles. Ethanol undergoes self-evaporation inside a capillary tube of borosilicate glass with internal diameter of 1 mm. The evaporation is not uniform along the meniscus interface pinned at the capillary tube mouth, and this creates a gradient of temperature between the wedge and the centre of the meniscus. It is this temperature difference and the scale (1 mm) that generate a gradient of surface tension that is acknowledged to drive the vigorous Marangoni convection in the meniscus liquid phase. In previous studies of this configuration, the meniscus has mainly been concave and for this reason, other researchers attributed the differential temperature along the meniscus to the fact that the meniscus wedge is closer to the tube mouth and also further away from the warmer liquid bulk than the meniscus centre. The present study investigates concave, flat and convex meniscus by using a syringe pump that forces the meniscus to the wanted shape. With the present investigation, we want to further demonstrate that it is instead the larger evaporation at the meniscus triple line near the wedge that controls the phenomenon. Flow visualization and infrared temperature measurements have been performed. For concave and convex meniscus, the temperature measurements are in line with the predicted trend; the Marangoni vortices for these two menisci shapes spin in the same direction according to the temperature differences along the meniscus. For a flat meniscus, an intriguing experimental evidence has been found: the temperature difference is inverted with respect to concave and convex menisci, but surprisingly, the Marangoni vortices spin in the same direction than for concave and convex menisci. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Experiments in Fluids Springer Journals

Marangoni convection in evaporating meniscus with changing contact angle

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Publisher
Springer Berlin Heidelberg
Copyright
Copyright © 2014 by Springer-Verlag Berlin Heidelberg
Subject
Engineering; Engineering Fluid Dynamics; Fluid- and Aerodynamics; Engineering Thermodynamics, Heat and Mass Transfer
ISSN
0723-4864
eISSN
1432-1114
D.O.I.
10.1007/s00348-014-1833-2
Publisher site
See Article on Publisher Site

Abstract

In this work, the Marangoni convection in the liquid phase of an evaporating meniscus interface in open air has been studied for varying contact angles. Ethanol undergoes self-evaporation inside a capillary tube of borosilicate glass with internal diameter of 1 mm. The evaporation is not uniform along the meniscus interface pinned at the capillary tube mouth, and this creates a gradient of temperature between the wedge and the centre of the meniscus. It is this temperature difference and the scale (1 mm) that generate a gradient of surface tension that is acknowledged to drive the vigorous Marangoni convection in the meniscus liquid phase. In previous studies of this configuration, the meniscus has mainly been concave and for this reason, other researchers attributed the differential temperature along the meniscus to the fact that the meniscus wedge is closer to the tube mouth and also further away from the warmer liquid bulk than the meniscus centre. The present study investigates concave, flat and convex meniscus by using a syringe pump that forces the meniscus to the wanted shape. With the present investigation, we want to further demonstrate that it is instead the larger evaporation at the meniscus triple line near the wedge that controls the phenomenon. Flow visualization and infrared temperature measurements have been performed. For concave and convex meniscus, the temperature measurements are in line with the predicted trend; the Marangoni vortices for these two menisci shapes spin in the same direction according to the temperature differences along the meniscus. For a flat meniscus, an intriguing experimental evidence has been found: the temperature difference is inverted with respect to concave and convex menisci, but surprisingly, the Marangoni vortices spin in the same direction than for concave and convex menisci.

Journal

Experiments in FluidsSpringer Journals

Published: Oct 11, 2014

References

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