title: Confinement effect on the dynamics of non-equilibrium concentration fluctuations far from the onset of convection.
abstract: 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.
authors.affiliation: Laboratoire des Fluides Complexes et leurs Réservoirs - UMR5150, Université de Pau et des Pays de l'Adour, 1 Allée du Parc Montaury, 64600, Anglet, France.|Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-Universität, 91052, Erlangen, Germany.
authors.forename: Cédric
authors.initials: C
authors.lastname: Giraudet
authors.affiliation: Laboratoire des Fluides Complexes et leurs Réservoirs - UMR5150, Université de Pau et des Pays de l'Adour, 1 Allée du Parc Montaury, 64600, Anglet, France.
authors.forename: Henri
authors.initials: H
authors.lastname: Bataller
authors.affiliation: Courant Institute of Mathematical Sciences, New York University, 10012, New York, NY, USA.
authors.forename: Yifei
authors.initials: Y
authors.lastname: Sun
authors.affiliation: Courant Institute of Mathematical Sciences, New York University, 10012, New York, NY, USA.
authors.forename: Aleksandar
authors.initials: A
authors.lastname: Donev
authors.affiliation: Departamento de Fısica Aplicada I, Facultad de Fısica, Universidad Complutense, 28040, Madrid, Spain.
authors.forename: José M
authors.initials: JM
authors.lastname: Ortiz de Zárate
authors.affiliation: Laboratoire des Fluides Complexes et leurs Réservoirs - UMR5150, Université de Pau et des Pays de l'Adour, 1 Allée du Parc Montaury, 64600, Anglet, France. fabrizio.croccolo@univ-pau.fr.|Centre National d'Études Spatiales (CNES) 2, Place Maurice Quentin, 75001, Paris, France. fabrizio.croccolo@univ-pau.fr.
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Croccolo
mesh_terms: D018481:Convection; D004058:Diffusion; D057446:Hydrodynamics; D008956:Models, Chemical; D013696:Temperature
keywords: Flowing Matter: Liquids and Complex Fluids