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Article Dans Une Revue Journal of Non-Newtonian Fluid Mechanics Année : 2014

Experimental investigation of the Rayleigh–Bénard convection in a yield stress fluid

Résumé

An experimental study of the Rayleigh-Bénard convection in a yield stress fluid (Carbopol Ò 980) uniformly heated from below in a rectangular cavity with high aspect ratio is presented. By combined integral measurements of the temperature difference between two parallel plates and the local flow velocity within a wide range of heating powers P two distinct regimes are observed. For heating powers smaller then a critical value P c a purely conductive regime is observed. A gradual increase of the heating power beyond this onset reveals a convective regime manifested through a nonlinear dependence of the temperature difference between plates on the heating power. Simultaneously with this, local measurements of the flow fields reveal a nonlinear increase of the roll pattern amplitude. Regardless the concentration of Carbopol Ò and in spite of a significant shear thinning behaviour, the Rayleigh-Bénard convection in the Carbopol Ò gel is found to emerge as an imperfect bifurcation that can be correctly modelled by the Landau theory of phase transitions. A critical slowing down phenomenon is observed corresponding to the onset of convection. The scaling laws of the convective onset P c and of the corresponding temperature difference DT c with the relevant material properties are discussed. The onset of the instability can be described in terms of a critical yield number rather than in terms of a critical Rayleigh number. The paper closes with a comparison of our findings with existing previous works.
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Dates et versions

hal-03146431 , version 1 (09-02-2023)

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Zineddine Kebiche, Cathy Castelain, Teodor Burghelea. Experimental investigation of the Rayleigh–Bénard convection in a yield stress fluid. Journal of Non-Newtonian Fluid Mechanics, 2014, 203, pp.9-23. ⟨10.1016/j.jnnfm.2013.10.005⟩. ⟨hal-03146431⟩
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