Stabilized convection in a ternary mixture with two Soret coefficients of opposite sign

Loreto García-Fernández (1) , Henri Bataller (1) , Paul Fruton (1) , Cédric Giraudet (1) , Alberto Vailati , Fabrizio Croccolo (1)

1 LFCR - Laboratoire des Fluides Complexes et leurs Réservoirs

Abstract We performed ground-based experiments on the sample polystyrene–toluene–cyclohexane in order to complement the experimental activities in microgravity conditions related to the ESA projects DCMIX4 and Giant Fluctuations. After applying a stabilizing thermal gradient by heating from above a layer of the fluid mixture, we studied over many hours the density variations in the bidimensional horizontal field by means of a Shadowgraph optical setup. The resulting images evidence the appearance of convective instability after a diffusive time associated with the binary molecular solvent consisting of toluene and cyclohexane, confirming the negative sign of the Soret coefficient of this mixture. After a larger diffusive time related to mass diffusion of the polystyrene in the binary solvent, convection was suppressed by the increasing stabilizing density gradient originated by the Soret-induced concentration gradient of the polymer. This is compatible with a positive sign of the Soret coefficient of the polymer in the binary solvent. Graphic Abstract

Domaines: Physique [physics]

Loreto García-Fernández, Henri Bataller, Paul Fruton, Cédric Giraudet, Alberto Vailati, et al.. Stabilized convection in a ternary mixture with two Soret coefficients of opposite sign. European Physical Journal E: Soft matter and biological physics, 2022, 45 (6), pp.52. ⟨10.1140/epje/s10189-022-00202-5⟩. ⟨hal-03974082⟩