Numerical simulation of the divergent flow regime in a circular contraction flow of a viscoelastic fluid

A numerical method is used to study the influence of inertiaand elongational properties on the vortex growth in the flowof a visco-elastic fluid through a four-to-one contraction.It appears that the vortex growth regime and the divergent flow regime,which are observed in experiments for some fluids, can be found for achoice of the material parameters where both the elongational stressesand the inertia forces are large for the flow rate considered.After studying the type and the vorticity it is concluded that theappearance of a divergent flow regime is likely to bea critical phenomenon (i.e. a change of type for a critical velocity)and that large elongational stresses are essential as well