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Journal Articles Physics of Fluids Year : 1995



The influence of particles on the first Rayleigh-Benard bifurcation from the motionless to the convective state has been studied in a suspension layer heated from below and cooled from above, and effective physical properties have been measured. The particle parameters are the diameter and the concentration. The experimental setup allows one to measure accurately the temperature and the heat flux and to computerize the data recording. The suspensions consisted of polystyrene particles (diameters 0.1, 0.2, 3, and 100 mu m and solid volume fraction from 1% to 10%) in water with the addition of surfactants and sodium sulphate for particles greater than 1 mu m. The onset of convection was detected by a change of the slope of the curves showing the heat flux versus the temperature difference. The experimental results show (i) a good agreement between the experimental values of effective thermal conductivity and the theoretical formulas, (ii) an increase of the convective threshold with a volume fraction that will be attributed to the stabilizing effects of the particles on the fluid (growth of the thermal relaxation time and decrease of the buoyancy time), and (iii) a nonmonotonous subcritical bifurcation for particles smaller than 1 mu m and supercritical bifurcation otherwise. (C) 1995 American Institute of Physics.
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hal-00638330 , version 1 (04-11-2011)



T. Girasole, R. Darrigo, Gérard Gouesbet, Claude Roze. 2-PHASE RAYLEIGH-BENARD INSTABILITIES. Physics of Fluids, 1995, 7 (11), pp.2659-2669. ⟨10.1063/1.868713⟩. ⟨hal-00638330⟩
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