Search

© 2017 Springer International Publishing AG. FC acknowledges fruitful discussions with Alberto Vailati, Doriano Brogioli and Roberto Cerbino. FC also acknowledges financial support from CNES. We acknowledge financial support from ESA through the SCCO program. JOZ acknowledges partial support from the Spanish State Secretary of Research under Grant No. FIS2014-58950-C2-2-P. AD was supported in part by the U.S. National Science Foundation under grant DMS-1115341 and the Office of Science of the U.S. Department of Energy through Early Career award number DE-SC0008271., In a recent letter (C. Giraudet et al., EPL 111, 60013 (2015)) we reported preliminary data showing evidence of a slowing-down of non-equilibrium fluctuations of the concentration in thermodiffusion experiments on a binary mixture of miscible fluids. The reason for this slowing-down was attributed to the effect of confinement. Such tentative explanation is here experimentally corroborated by new measurements and theoretically substantiated by studying analytically and numerically the relevant fluctuating hydrodynamics equations. In the new experiments presented here, the magnitude of the temperature gradient is changed, confirming that the system is controlled solely by the solutal Rayleigh number, and that the slowing-down is dominated by a combined effect of the driving force of buoyancy, the dissipating force of diffusion and the confinement provided by the vertical extension of the sample cell. Moreover, a compact phenomenological interpolating formula is proposed for easy analysis of experimental results., Ministerio de Ciencia e Innovación (MICINN), CNES, ESA through the SCCO program, U.S. National Science Foundation, Office of Science of the U.S. Department of Energy, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub