Elastic and shear-thinning effects in contraction flows: a comparison

The flow through a 4:1 planar contraction has been investigated using different rheological models having the same shear viscosity, namely, the inelastic Carreau-Yasuda model (CY), the enhanced Bautista-Manero-Puig (eBMP), and the exponential version of the Phan-Thien/Tanner (PTT). Noticeable discrepancies were observed with the CY model and the eBMP in terms of the velocity profiles along the centerline and in the exit channel (near the end of the geometry) normal to the flow direction. Transient planar extensional viscosity shows a large effect on vortex dynamics although the effect of transient and steady elongation on pressure drop seems negligible. Simulation results allowed gathering that pressure drop is largely influenced by the shear-thinning behavior of the fluid, noticeably affected by elasticity, and less by extensional viscosity.