Journal of Fluid Mechanics



Investigation of thermocapillary convection in a three-liquid-layer system


Ph. GÉORIS a1, M. HENNENBERG a1, G. LEBON a2 and J. C. LEGROS a1
a1 Université Libre de Bruxelles, Service de Chimie Physique EP, CP165-62, 50 Av F. D. Roosevelt 1050, Brussels, Belgium
a2 Université de Liège, Institut de Physique B5 Sart Tilman, B 4000 Liège 1, Belgium

Abstract

This paper presents the first experimental results on Marangoni–Bénard instability in a symmetrical three-layer system. A pure thermocapillary phenomenon has been observed by performing the experiment in a microgravity environment where buoyancy forces can be neglected. This configuration enables the hydrodynamic stability of two identical liquid–liquid interfaces subjected to a normal gradient of temperature to be studied. The flow is driven by one interface only and obeys the criterion based on the heat diffusivity ratio proposed by Scriven & Sternling (1959) and Smith (1966). The measured critical temperature difference for the onset of convection is compared to the value obtained from two-dimensional numerical simulations. The results of the simulations are in reasonable agreement with the velocimetry and the thermal experimental data for moderate supercriticality. Numerically and experimentally, the convective pattern exhibits a transition between different convective regimes for similar temperature gradients. Their common detailed features are discussed.

(Received March 6 1997)
(Revised January 7 1999)



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