Influence of inertia and viscoelasticity in entry flows through an abrupt annular contraction

A numerical simulation of entry flows in an annular die has been undertaken for Newtonian and power-law fluids as well as viscoelastic fluids that exhibit normal stresses in shear flow. Experimentally measured normal stress and viscosity data are included in a simple rheological model. The influence of inertia and viscoelasticity are examined separately as functions of the Reynolds (Re) and Weissenberg (Ws) numbers. It is found that inertia decreases the size of the corner vortices in the reservoir corners which tend to increase rapidly with elasticity level in the absence of inertia. The combined effect of inertia and elastic forces is to first increase the vortex size followed by a decrease at higher Re numbers. The numberical simulations are in qualitative agreement with experimental studies available in the literature.