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García-Fernández L, Bataller H, Fruton P, Giraudet C, Vailati A, Croccolo F. Stabilized convection in a ternary mixture with two Soret coefficients of opposite sign. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2022; 45:52. [PMID: 35633426 PMCID: PMC9148296 DOI: 10.1140/epje/s10189-022-00202-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Accepted: 04/27/2022] [Indexed: 06/15/2023]
Abstract
We performed ground-based experiments on the sample polystyrene-toluene-cyclohexane in order to complement the experimental activities in microgravity conditions related to the ESA projects DCMIX4 and Giant Fluctuations. After applying a stabilizing thermal gradient by heating from above a layer of the fluid mixture, we studied over many hours the density variations in the bidimensional horizontal field by means of a Shadowgraph optical setup. The resulting images evidence the appearance of convective instability after a diffusive time associated with the binary molecular solvent consisting of toluene and cyclohexane, confirming the negative sign of the Soret coefficient of this mixture. After a larger diffusive time related to mass diffusion of the polystyrene in the binary solvent, convection was suppressed by the increasing stabilizing density gradient originated by the Soret-induced concentration gradient of the polymer. This is compatible with a positive sign of the Soret coefficient of the polymer in the binary solvent.
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Affiliation(s)
- Loreto García-Fernández
- E2S UPPA, CNRS, TotalEnergies, LFCR UMR5150, Universite de Pau et des Pays de l’Adour, Anglet, France
- Centre National d’Études Spatiales (CNES), 2, Place Maurice Quentin, Paris, France
- Department of Structure of Matter, Thermal Physics and Electronics, Faculty of Physics, University Complutense of Madrid, Madrid, Spain
| | - Henri Bataller
- E2S UPPA, CNRS, TotalEnergies, LFCR UMR5150, Universite de Pau et des Pays de l’Adour, Anglet, France
| | - Paul Fruton
- E2S UPPA, CNRS, TotalEnergies, LFCR UMR5150, Universite de Pau et des Pays de l’Adour, Anglet, France
| | - Cédric Giraudet
- E2S UPPA, CNRS, TotalEnergies, LFCR UMR5150, Universite de Pau et des Pays de l’Adour, Anglet, France
| | - Alberto Vailati
- Dipartimento di Fisica “A. Pontremoli”, Università degli Studi di Milano, Milan, Italy
| | - Fabrizio Croccolo
- E2S UPPA, CNRS, TotalEnergies, LFCR UMR5150, Universite de Pau et des Pays de l’Adour, Anglet, France
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Abstract
The Soret effect describes the transport of constituent species in multicomponent mixtures that occurs due to a temperature gradient. This cross-coupling effect of heat and mass transfer has been successfully examined in binary liquid mixtures, while experiments with ternary mixtures are rare as they impose significant difficulties. We introduce a new and innovative concept, the Soret vector, for the characterization of Soret driven separation in ternary mixtures. The presentation of the component separation in the vector form offers several advantages: (i) to predict the Soret sign of a ternary mixture from knowledge of the Soret coefficients in binary subsystems; (ii) to control consistency of measured coefficients, this is especially important when results are obtained using different instruments and methods; (iii) to determine in which regions and which components cause the greatest separation; (iv) to identify the regions where the Soret separation is inaccessible for optical techniques or gravitationally unstable. We demonstrate these features by exploring ternary mixtures of different origins: (a) nearly ideal mixture composed by THN–IBB–nC12 when Soret coefficients in binary subsystems (\documentclass[12pt]{minimal}
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\begin{document}$$S_{T}^{bin}$$\end{document}STbin) are positive, (b) non-ideal mixture containing water and ethanol TEG–Wat–EtOH when \documentclass[12pt]{minimal}
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\begin{document}$$S_{T}^{bin}$$\end{document}STbin are positive and negative and (c) Tol–MeOH–Ch mixture containing demixing zone with positive and negative \documentclass[12pt]{minimal}
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\begin{document}$$S_{T}^{bin}$$\end{document}STbin. Our approach provides a promising systematic framework for the future research of an important and challenging problem of thermodiffusion in multicomponent liquids.
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Prokopev S, Lyubimova T, Mialdun A, Shevtsova V. A ternary mixture at the border of Soret separation stability. Phys Chem Chem Phys 2021; 23:8466-8477. [PMID: 33876010 DOI: 10.1039/d0cp06471h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ternary mixtures with the Soret effect are prone to triple-diffusive convection in a thermal field. The Soret coefficients of the toluene-methanol-cyclohexane mixture, measured in microgravity at a given composition [0.62-0.31-0.07] in mass fractions, showed that the net separation ratio, Ψ, the parameter responsible for the hydrodynamic stability in a gravity field is close to zero. Furthermore, the large cross-diffusion of toluene leads to a curious situation: the Soret coefficient ST1 is positive while the thermodiffusion coefficient DT1 is negative. The behavior of this ternary mixture on the border of stability, when Ψ is slightly negative or positive, is examined experimentally and numerically. The mixture is placed in an elongated cell between the differently heated walls. Depending on Ψ and the initial temperature of the liquid (mean temperature, linear profile or cold one), the evolution of concentration patterns are classified by four regimes. We observe the emergence of motionless, metastable, and convective patterns. In the case of Ψ > 0, it was found that cross-diffusion fluxes cause a temporarily unstable density pattern. The initially cold mixture at either Ψ sign shows dissimilar Soret separation in the upper and lower parts of the cell. It leads to the formation of a long-lived inverse density gradient at the upper part of the cell, which finally results in a motionless (Ψ > 0) or convective (Ψ < 0) pattern.
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Affiliation(s)
- Sergei Prokopev
- Institute of Continuous Media Mechanics UB RAS, Perm, Russia
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Bresme F, Vesovic V, Bataller H, Croccolo F. Topical Issue on Thermal Non-Equilibrium Phenomena in Soft Matter. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2019; 42:148. [PMID: 31754843 DOI: 10.1140/epje/i2019-11918-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Accepted: 11/20/2019] [Indexed: 06/10/2023]
Affiliation(s)
- Fernando Bresme
- Department of Chemistry, Imperial College London, White City Campus, W12 0BZ, London, UK
| | - Velisa Vesovic
- Department of Earth Science & Engineering, Imperial College London, South Kensington Campus, SW7 2AZ, London, UK
| | - Henri Bataller
- Laboratoire des Fluides Complexes et leurs Réservoirs, IPRA, UMR5150, E2S-Univ Pau and Pays Adour/CNRS/Total, 1 Allée du Parc Montaury, 64600, Anglet, France
| | - Fabrizio Croccolo
- Laboratoire des Fluides Complexes et leurs Réservoirs, IPRA, UMR5150, E2S-Univ Pau and Pays Adour/CNRS/Total, 1 Allée du Parc Montaury, 64600, Anglet, France
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García-Fernández L, Fruton P, Bataller H, Ortiz de Zárate JM, Croccolo F. Coupled non-equilibrium fluctuations in a polymeric ternary mixture. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2019; 42:124. [PMID: 31511999 DOI: 10.1140/epje/i2019-11889-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Accepted: 08/14/2019] [Indexed: 06/10/2023]
Abstract
We investigate by dynamic shadowgraphy the non-equilibrium fluctuations at the steady state of a thermodiffusion experiment in a polymeric ternary mixture of polystyrene-toluene-n-hexane. The structure function of the refractive index reveals the existence of quite different decay times, thus requiring the analysis of a wide range of correlation times. This is related to the simultaneous presence of three distinct decay modes corresponding to (from fastest to slowest) the relaxation of temperature fluctuations, of the concentration fluctuations of the mixed solvent, and of the concentration fluctuations of the polymer in the binary solvent. An investigation of the decay times at the corresponding diffusive regimes provides a measurement of the thermal diffusivity and the two eigenvalues of the mass diffusion matrix of the ternary mixture. Similar experiments were performed in the past but here, to suppress the confinement effect and obtain a more direct comparison with the theory, a thicker sample is studied. Moreover, also a faster camera is used allowing the experimental observation of faster modes, like the propagative ones. The experimental values of the decay times are eventually compared with those predicted by different available theories. Finally, we present a more complete theoretical model to describe the non-equilibrium fluctuations in the bulk of a ternary mixture at the steady state of a thermodiffusion experiment.
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Affiliation(s)
- L García-Fernández
- Laboratoire des Fluides Complexes et leurs Réservoirs - IPRA, UMR5150, E2S-Univ Pau & Pays Adour/CNRS/Total, 1 Allée du Parc Montaury, 64600, Anglet, France.
- Centre National d'Études Spatiales (CNES), 2, Place Maurice Quentin, 75001, Paris, France.
| | - P Fruton
- Laboratoire des Fluides Complexes et leurs Réservoirs - IPRA, UMR5150, E2S-Univ Pau & Pays Adour/CNRS/Total, 1 Allée du Parc Montaury, 64600, Anglet, France
| | - H Bataller
- Laboratoire des Fluides Complexes et leurs Réservoirs - IPRA, UMR5150, E2S-Univ Pau & Pays Adour/CNRS/Total, 1 Allée du Parc Montaury, 64600, Anglet, France
| | - J M Ortiz de Zárate
- Departamento de Estructura de la Materia, Física Térmica y Electrónica, Facultad de Ciencias Físicas, Universidad Complutense de Madrid, Plaza de las Ciencias 1, 28040, Madrid, Spain
| | - F Croccolo
- Laboratoire des Fluides Complexes et leurs Réservoirs - IPRA, UMR5150, E2S-Univ Pau & Pays Adour/CNRS/Total, 1 Allée du Parc Montaury, 64600, Anglet, France
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