On the performance of enhanced constitutive models for polymer melts in a cross-slot flow

A new class of viscoelastic constitutive equations is proposed that provide s enhanced control of shear and elongational properties. Together with the widely used Giesekus and Phan-Thien Tanner model, these enhanced models are evaluated for a polymer melt (LDPE) in a cross-slot flow. This stagnation flow has a strong planar elongational deformation component. The material i s characterized, in both viscometric simple shear flow and in uniaxial elon gation. Velocities are measured with particle tracking velocimetry while fi eld-wise flow-induced birefringence is used for correlation with stresses. The experimental results are compared with 2D viscoelastic simulations. Wit h equal quality of describing viscometric data, the enhanced models can pre dict the flow properties of the cross-slot flow significantly better than t he well known PTT and Giesekus model. (C) 1999 Elsevier Science B.V. All ri ghts reserved.