Three-dimensional absolute and convective instabilities in mixed convection of a viscoelastic fluid through a porous medium |
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Authors: | Sílvia C Hirata |
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Institution: | Laboratoire de Mécanique de Lille, UMR CNRS 8107 - Université Lille I, Bld. Paul Langevin, 59655 Villeneuve d'Ascq cedex, France |
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Abstract: | By using the mathematical formalism of absolute and convective instabilities we study the nature of unstable three-dimensional disturbances of viscoelastic flow convection in a porous medium with horizontal through-flow and vertical temperature gradient. Temporal stability analysis reveals that among three-dimensional (3D) modes the pure down-stream transverse rolls are favored for the onset of convection. In addition, by considering a spatiotemporal stability approach we found that all unstable 3D modes are convectively unstable except the transverse rolls which may experience a transition to absolute instability. The combined influence of through-flow and elastic parameters on the absolute instability threshold, wave number and frequency is then determined, and results are compared to those of a Newtonian fluid. |
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Keywords: | Mixed convection Absolute instability Viscoelastic fluid Porous medium |
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