A ternary mixture at the border of Soret separation stability
| Autor: | Aliaksandr Mialdun, Valentina Shevtsova, Sergei Prokopev, Tatyana Lyubimova |
|---|---|
| Rok vydání: | 2021 |
| Předmět: |
Convection
Hydrodynamic stability Materials science Field (physics) Density gradient General Physics and Astronomy Thermodynamics 02 engineering and technology 021001 nanoscience & nanotechnology 01 natural sciences Thermophoresis 010305 fluids & plasmas Physics::Fluid Dynamics Physico-chimie générale Metastability 0103 physical sciences Thermal Physical and Theoretical Chemistry 0210 nano-technology Ternary operation |
| Zdroj: | PCCP. Physical chemistry chemical physics, 23 (14 |
| ISSN: | 1463-9084 1463-9076 |
| Popis: | 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. info:eu-repo/semantics/published |
| Databáze: | OpenAIRE |
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