The Soret coefficients of the ternary system water/ethanol/triethylene glycol and its corresponding binary mixtures

Thermodiffusion in ternary mixtures is considered prototypic for the Soret effect of truly multicomponent systems. We discuss ground-based measurements of the Soret coefficient along the binary borders of the Gibbs triangle of the highly polar and hydrogen bonding ternary DCMIX3-system water/ethanol/triethylene glycol. All three Soret coefficients decay with increasing concentration, irrespective of the choice of the independent component, and show a characteristic sign change as a function of temperature and/or composition. With the exception of triethylene glycol/ethanol at high temperatures, the minority component always migrates toward the cold side. All three binaries exhibit temperature-independent fixed points of the Soret coefficient. The decay of the Soret coefficient with concentration can be related to negative excess volumes of mixing. The sign changes of the Soret coefficients of the binaries allow to draw far-reaching conclusions about the signs of the Soret coefficients of the corresponding ternary mixtures. In particular, we show that at least one ternary composition must exist, where all three Soret coefficients vanish simultaneously and no steady-state separation is observable

Accumulation of particles in time-dependent thermocapillary flow in a liquid bridge. Modeling of experiments.

The study addresses the phenomenon of accumulation of rigid tracer particles suspended in a time-dependent thermocapillary flow in a liquid bridge. We report the results of the three-dimensional numerical modeling of recent experiments in a non-isothermal liquid column. Exact physical properties of both liquids and particles are used for the modeling. Two liquids are investigated: sodium nitrate and n-decane. The particles are modeled as perfect spheres suspended in already well developed time-dependent thermocapillary flow. The particle dynamics is described by the Maxey-Riley equation. The results of our simulations are in excellent agreement with the experimental observations. For the first time we reproduced numerically formation of the particle accumulation structure (PAS) both under gravity and under weightlessness conditions. Our analysis confirms the experimental observations that the existence of PAS depends on the strength of the flow field, on the ratio between liquid and particle density, and on the particle size.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Termo- and solutocapillary convection in a cylindrical liquid bridge: stability of steady axisymmetric flow

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Convective Instability mechanism in thermocapillary liquid bridges

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Energy analysis of some flow instabilities in liquid bridges

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The Measurement of Soret and Thermodiffusion Coefficients in Binary and Ternary Liquid Mixtures

Abstract This review provides an overview of the major, currently used techniques for investigating the Soret effect and measuring thermodiffusion and Soret coefficients, and in most cases also isothermal Fickian diffusion coefficients, in liquid mixtures. The methods are introduced with a focus on binary mixtures. The optical methods comprise optical beam deflection (OBD), optical digital interferometry (ODI) both on the ground and under microgravity conditions in the SODI-IVIDIL experiment for the study of the influence of vibrations onboard the International Space Station, which are all based on Soret cells. The transient holographic grating technique of thermal diffusion-forced Rayleigh scattering (TDFRS) employs light not only for detection of the concentration changes but also for optical volume heating. Thermogravitational columns (TGC) utilize the coupling between convection and thermodiffusion to create concentration changes inside a vertical column with a horizontal temperature gradient. While samples are analyzed after extraction from the column in a classical setup, the recently developed transparent microcolumn allows for interferometric in situ monitoring of the concentration field. The most recent technique relies on the measurement of giant non-equilibrium fluctuations (NEFs) by small-angle light scattering techniques. Research on ternary mixtures, both on the ground and in microgravity, has gained momentum in the context of the DCMIX microgravity project of ESA. Most techniques employed for binaries can be extended to ternaries by introducing a second detection color or by analyzing both refractive index and density of extracted TGC samples. The accuracy is limited by the unavoidable inversion of the so-called contrast factor matrix.info:eu-repo/semantics/publishe

Diffusion, thermal diffusion, and Soret coefficients and optical contrast factors of the binary mixtures of dodecane, isobutylbenzene, and 1,2,3,4-tetrahydronaphthalene

We have measured the Soret (ST), diffusion (D), and thermal diffusion (DT) coefficients of the three binary benchmark mixtures of dodecane (C12), isobutylbenzene, and 1,2,3,4-tetrahydronaphthalene at T 25°C for at least five different concentrations each, covering the entire binary composition range. The two different optical techniques employed, optical beam deflection and optical digital interferometry, are in good to excellent agreement. Additionally, we have carefully measured the optical contrast factors (nc)p, T and (nT)p, c. If the temperature and composition dependence of the mixture density is taken into account, both the Lorentz-Lorenz (LL) and the Looyenga (LO) equations give reasonable predictions of (nc)p, T. In case of (nT)p, c, only the LO equation yields good predictions in case of constant molecular polarizabilities αi of the pure compounds. If the apparent temperature dependence of αi is explicitly taken into account, excellent predictions are obtained both from the LL and the LO equations. © 2013 American Institute of Physics.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Thermocapillary motion and stability of liquid bridges

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Onset of Hydrothermal Instability in Liquid Bridge: Experimental Benchmark

The experimental results from nine benchmark test cases conducted by five different groups are presented. The goal of this study is to build an experimental database for validation of numerical models in liquid bridge geometry. The need arises as comparison of numerical results with a single experiment can lead to a large discrepancy due to specific experimental conditions. Perfectly conducting rigid walls and, especially, idealized boundary conditions at the free surface employed in numerical studies are not always realized in experiments. The experimental benchmark has emphasized strong sensitivity of the threshold of instability to the liquid bridge shape. A clear distinction should be made between results belonging to the different disturbance patterns, i.e. different wave numbers. The results of benchmark contributors are in a satisfactory agreement when they are associated with the stability branch with an identical wave number. In this case the discrepancy of the results for determination of the critical parameters is about ±15%-18% and they can be used for the validation of numerical models. © 2011 Tech Science Press.En ligne: http://www.techscience.com/paper.asp?jnl=fdmp&issue=v7n1&no=01SCOPUS: ar.jinfo:eu-repo/semantics/publishe