Browsing by Author "Escudier, M. P."
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- Fully developed laminar flow of non-Newtonian liquids through annuli: comparison of numerical calculations with experiments.Publication . Escudier, M. P.; Oliveira, Paulo J.; Pinho, Fernando; Smith, S.Experimental data are reported for fully developed laminar flow of a shear-thinning liquid through both a concentric and an 80% eccentric annulus with and without centrebody rotation. The working fluid was an aqueous solution of 0.1% xanthan gum and 0.1% carboxymethylcellulose for which the flow curve is well represented by the Cross model. Comparisons are reported between numerical calculations and the flow data, as well as with other laminar annular-flow data for a variety of shear-thinning liquids previously reported in the literature. In general, the calculations are in good quantitative agreement with the experimental data, even in situations where viscoelastic effects, neglected in the calculations, would be expected to play a role.
- Laminar flow of a viscoelastic shear-thinning liquid through a plane sudden expansion preceded by a gradual contractionPublication . Poole, R. J.; Escudier, M. P.; Oliveira, Paulo J.Experimental observations are reported for the laminar flow of a viscoelastic liquid through a symmetrical plane sudden expansion preceded by a gradual contraction from a square duct. As is well known, for Newtonian fluid flow above a critical Reynolds number the flowfield downstream of an expansion becomes asymmetric. For the viscoelastic liquid investigated here the asymmetry is greatly reduced, with very similar reattachment lengths for the two recirculation regions. More significantly, the flow unexpectedly develops a strongly three-dimensional jet-like structure, with side-to-side symmetry centred on the ‘vertical’ symmetry plane of the contraction/expansion geometry. Especially interesting is the flow within the contraction itself, where the nature of the flow field for the viscoelastic liquid is also fundamentally different to that for a comparable Newtonian fluid flow: large velocity overshoots with very strong gradients occur near to the sidewalls that, due to their appearance, we have termed ‘cat’s ears’. The fully developed approach flow in the square duct is unremarkable.