RT Journal Article
SR Electronic
T1 Laminar flow of a viscoelastic shear-thinning liquid through a plane sudden expansion preceded by a gradual contraction
JF Proceedings of the Royal Society A: Mathematical, Physical and Engineering Science
JO PROC R SOC A
FD The Royal Society
SP 3827
OP 3845
DO 10.1098/rspa.2005.1535
VO 461
IS 2064
A1 Poole, R.J
A1 Escudier, M.P
A1 Oliveira, P.J
YR 2005
UL http://rspa.royalsocietypublishing.org/content/461/2064/3827.abstract
AB 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.