Laplace pressure evolution and four instabilities in evaporating two-grain liquid bridges
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© 2015 Elsevier B.V.Dynamic variables characterizing evolution during evaporation of capillary bridge between two spheres are analyzed. The variables include: average Laplace pressure, pressure resulting force, surface tension force and total capillary force calculated based on the previously reported geometrical variables using Young-Laplace law [1,2]. This is the first time to our knowledge that Laplace pressure is calculated from the measured bridge curvatures along the process of evaporation and compared to experimental measurement data. A comparison with the experimental data from analogous capillary bridge extension tests is also shown and discussed.The behavior of evaporating liquid bridges is seen as strongly dependent on the grain separation. Initial negative Laplace pressure at small separations is seen to significantly augment during an advanced stage of evaporation, but to turn into positive pressure, after an instability toward the end of the process, and prior to rupture. At larger separations the pressure is positive all the time, changing a little, but rupturing early. Rupture in all cases occurs at positive pressure. However, because of the evolution of the surface area of contact, the resultant total capillary forces are always tensile, and decreasing toward zero in all cases. Comparison between measured total resultant capillary forces and those calculated from the Young-Laplace law is very good, except for some discrepancies at very small separations (below 50. μm). Up to four consecutive instabilities of capillary bridge are seen developing at some sphere separations. They are: re-pinning-induced suction (pressure) instability; Rayleigh nodoid/catenoid/unduloid unstable transition, associated with zero-pressure; Rayleigh unduloid/cylinder unstable transition, associated with the formation of a liquid-wire; and lastly, a pinching instability of the liquid-wire, associated with the bridge rupture. Rupture of the bridges is seen at large separations to occur quite early, at only 1/4-1/3 of the initial water volume evaporated. At smallest separations, rupture occurs in a seemingly unstable way when water evaporates from the bridge thinnest section of the neck.
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Mielniczuk, B, T Hueckel and MS El Youssoufi (2015). Laplace pressure evolution and four instabilities in evaporating two-grain liquid bridges. Powder Technology, 283. pp. 137–151. 10.1016/j.powtec.2015.05.024 Retrieved from https://hdl.handle.net/10161/10757.
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Tomasz Hueckel
Tomasz Hueckel received his master's degree in civil engineering from the University of Technology in Gdansk, Poland, in 1968, his Ph.D. in applied mechanics from the Polish Academy of Sciences in Warsaw, in 1974, and the D.Sc. in physical sciences from the University of Grenoble, France, in 1985. He started his research career at the Polish Academy of Sciences in Warsaw, then taught at the University of Rome and the University of Technology in Milan before joining ISMES, a research institute in Bergamo, Italy, where he was responsible for research on geomechanical aspects of nuclear waste disposal in clays, a subject in which he continues to be strongly involved. He came to Duke in 1987.
Dr. Hueckel's research interest is in theoretical soil mechanics, rock mechanics, and environmental geomechanics, as well as in theory of plasticity. His current projects deal with thermo-plasticity and chemo-plasticity of clays, and in general in mechanics of materials composed of chemically reacting solids and liquids. He is interested in fundamental aspects of soil drying and cracking, and processes of soil aging and healing. The above subjects involve mathematical modeling and model driven laboratory experiments. He also is interested in basic aspects of theory of plasticity, such as stability and localization. His research is applied to hydraulic geo-barriers affected either by chemically hazardous liquids or nuclear waste heat, to prediction of petroleum production induced compaction and subsidence, as well as desiccation damage.
Dr. Hueckel is a co-founder and co-Editor-in Chief (2015) of Geomechanics for Energy and the Environment, an Elsevier journal. He has published also in International Journal of Solids and Structures, International Journal of Engineering Science, Pure and Applied Geophysics, Surveys in Geophysics, Engineering Geology, Engineering Fracture Mechanics, International Journal of Rock Mechanics and Mining Engineering, International Journal of Numerical and Analytical Methods in Geomechanics, Computers and Geotechnics, International Journal of Soils and Foundations, Journal de Mecanique, Canadian Geotechnical Journal, Meccanica, Ingenieur- Archiv, and the ASCE Journal of Geotechnical Engineering. He has also contributed to numerous books on the state of the art. Dr. Hueckel is heavily involved in international research cooperation, collaborating and co-authoring with Belgian, Italian, French, Polish, Spanish and Swiss researchers. He is or was a member of the editorial board of the Journal of Numerical and Analytical Methods in Geomechanics, the Archive of Applied Mechanics and of the International Journal of Mechanics of Cohesive and Frictional Materials, ASCE Journals of Geotechnical and Geoenvironmental Engineering and ASCE International Journal of Geomechanics, Italian Geotechnical Journal and Studia Geotechnica et Mechanica (Polish).
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