Laminar viscoelastic flow over a backward-facing step

Content Provider	Semantic Scholar
Author	Poole, Robert J. Escudier, Marcel Afonso, Alexandre Pinho, Fernando T.
Copyright Year	2004
Abstract	The results are reported of an experimental investigation of the laminar flow of a series of viscoelastic liquids, 0.05%, 0.1% and 0.4% w/w/ aqueous solutions of polyacrylamide (Seperan AP 273 E), through a plane sudden expansion, of expansion ratio, R=D/d=1.43, immediately preceded by a smooth contraction. The two lower concentrations, 0.05% and 0.1%, are at essentially the same Reynolds number (ca. 120, based on a characteristic viscosity corresponding to UB/h) and demonstrate the effect of increasing concentration on the flow field for a situation with a relatively high degree of inertia (at least in comparison to previous studies which were for very low (∼1) Re). As concentration increases the reattachment length is decreased from 7.25 h for 0.05% PAA to less than 3h for 0.1% PAA, as are the magnitudes of the recirculating velocities i.e. recirculation is suppressed. For the highest concentration (0.4% PAA, Re≈5) the flow field downstream of the expansion is devoid of recirculation and this is a consequence of the viscoelasticity of the liquid damping out vortex activity. The effect of the smooth contraction that precedes the expansion is more thought provoking. The velocity profile produced by the contraction is intriguing, with velocity overshoots near the sidewall for 0.05% and 0.1% PAA and being more pyramidal in shape for 0.4% PAA as opposed to the uniform shape of a Newtonian fluid-flow, and attempts are made to understand the physical processes causing these profiles and to relate this to degree of viscoelasticity of the liquid.
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Alternate Webpage(s)	http://pcwww.liv.ac.uk/~robpoole/papers/poole_conf_8.pdf
Alternate Webpage(s)	https://web.fe.up.pt/~fpinho/pdfs/NF06.pdf
Language	English
Access Restriction	Open
Content Type	Text
Resource Type	Article