Analysis of Non-Equilibrium Fluctuations In A Ternary Liquid Mixture

• Published in: Microgravity science and technology 2016-12, Vol.28 (6), p.611-619
• Main Authors: Bataller, Henri, Giraudet, Cédric, Croccolo, Fabrizio, Ortiz de Zárate, José Maria
• Format: Article
• Language: English
• Subjects: Advances in gravity-related phenomena in biological; Aerospace Technology and Astronautics; chemical and physical systems; Classical and Continuum Physics; Decay; Earth Sciences; Engineering; Engineering Sciences; Fluctuations; Fluids mechanics; Geophysics; Mechanical engineering; Mechanics; Mechanics of materials; Original Article; Physics; Sciences of the Universe; Space Exploration and Astronautics; Space Sciences (including Extraterrestrial Physics; Thermal diffusivity
• ISSN: 0938-0108; 1875-0494
• DOI: 10.1007/s12217-016-9517-6

From the benchmark values of the diffusion and thermodiffusion coefficients of the tetralin, isobutylbenzene and n-dodecane ternary mixture, and the published optical contrast factors, we have evaluated the theoretical amplitudes of the two composition modes of the refractive-index fluctuations. Shadowgraph experiments have been performed on ground, where the current theory is expected to be correct only for large wave vectors. Two decay times have been observed experimentally. The fastest one being related to the thermal diffusivity of the mixture, while the slower one to mass diffusion. Hence, it has not been possible to distinguish the two eigenvalues of the mass diffusion matrix, a problem also encountered in traditional light-scattering with ternary mixtures of similar-size molecules. Thus, to compare the measured Intermediate Scattering Function with theory, we fix the amplitudes and decay rates to the benchmark values, use the wave number as a fitting parameter, and compare it to the experimental wave number. The good agreement between theory and experiments for the larger wave numbers validates the theory developed for the microgravity conditions.