Effect of Contraction Width on the Vortex Formation of Viscoelastic Flow in Asymmetric Planar Contractions

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In this paper, the flow behavior of viscoelastic fluid in asymmetric planar contraction geometry is studied by flow visualization and PIV measurement. Experiments are carried out for three channels of different contraction widths. The experimental results indicate that the flow field in the contraction channel is characterized by the Weissenberg number to Newtonian-like flow, transitional flow and vortex formation flow. It is found that the vortex formation flow occurs over the critical Weissenberg number, which is independent of the Reynolds number. However, the critical Weissenberg number decreases with increasing the contraction width due to the influence of velocity acceleration in the entry channel in the upstream of the contraction.