Rayleigh-Bénard convection in non-Newtonian fluids: Experimental and theoretical investigations
| Autor: | Mondher Bouteraa, Simon Becker, Jamal Ouhajjou, Thomas Varé, Chérif Nouar |
|---|---|
| Přispěvatelé: | Laboratoire Énergies et Mécanique Théorique et Appliquée (LEMTA ), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS) |
| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: |
Fluid Flow and Transfer Processes
Convection Physics Mechanical Engineering Prandtl number Computational Mechanics Radius Mechanics Condensed Matter Physics Critical value 01 natural sciences Non-Newtonian fluid 010305 fluids & plasmas Physics::Fluid Dynamics symbols.namesake [SPI]Engineering Sciences [physics] Mechanics of Materials 0103 physical sciences Newtonian fluid symbols [PHYS.MECA.THER]Physics [physics]/Mechanics [physics]/Thermics [physics.class-ph] Shadowgraph 010306 general physics Rayleigh–Bénard convection |
| Zdroj: | Physics of Fluids Physics of Fluids, American Institute of Physics, 2021, 33, pp.114112. ⟨10.1063/5.0070983⟩ |
| ISSN: | 1070-6631 1089-7666 |
| DOI: | 10.1063/5.0070983⟩ |
| Popis: | We present an experimental and theoretical study of Rayleigh–Benard convection in shear-thinning fluids with temperature-dependent properties. Experiments were performed using a cylindrical cell with a radius R=60 mm and height adjustable at d=15 and 20 mm giving a radius-to-height ratio L = 4 and 3, respectively. The fluids used are glycerol (Newtonian fluid) and aqueous xanthan gum solutions (shear-thinning fluids) at 1000 and 1200 ppm. Convection patterns are visualized by the shadowgraph method. In the theoretical part of this study, the weakly nonlinear analysis performed by Vare et al. [J. Fluid Mech. 905, A33 (2020)] is extended to take into account the variation of the thermal expansion coefficient with temperature. For the xanthan gum solutions used, the temperature dependence of the fluid parameters is sufficiently strong to obtain hexagonal cells at the onset of convection. It has been observed that their size decreases with the increase in the temperature difference across the fluid layer above the critical value. This result provides an experimental support to our theoretical study where it is shown that for hexagons, the band of stable wavenumbers is bent toward higher wavenumbers. For the glycerol, Newtonian fluid with a large Prandtl number, a slight increase in the wavelength of rolls is observed in agreement with the literature. |
| Databáze: | OpenAIRE |
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