Eur. Phys. J. E (2017) 40: 22
https://doi.org/10.1140/epje/i2017-11513-9

Regular Article

Gravity effects on Soret-induced non-equilibrium fluctuations in ternary mixtures

¹ Departamento de Física Aplicada I, Universidad Complutense, Plaza de las Ciencias 1, 28040, Madrid, Spain
² Laboratoire des Fluides Complexes et leurs Réservoirs - UMR5150, Université de Pau et des Pays de l’Adour, 64600, Anglet, France
³ Centre National d’Etudes Spatiales (CNES), 2 Place Maurice Quentin, 75001, Paris, France

^* e-mail: pablomartinezpancorbo@gmail.com

Received: 27 September 2016
Accepted: 6 February 2017
Published online: 28 February 2017

Abstract

We discuss the gravity effects on the dynamics of composition fluctuations in a ternary mixture around the non-equilibrium quiescent state induced by thermodiffusion when subjected to a stationary temperature gradient. We found that the autocorrelation matrix of concentration fluctuations can be expressed as the sum of two exponentially decaying concentration modes. Without accounting for confinement, we obtained exact analytical expressions for the two decay rates which, as a consequence of gravity, display a wave-number-dependent mixing. The stability of the quiescent solution is also examined, as a function of the two solutal Rayleigh numbers used to express the decay rates. After having discussed the dynamics of the two concentration modes, we calculate the corresponding amplitudes. Consequences for optical experiments are discussed.