Numerical Simulation and Experiment of Polyethylene Melt Flow in Capillary

Two differential viscoelastic constitutive models, DCPP model and S-MDCPP model, were used to simulate the flow of linear low-density polyethylene melts in capillary rheometer, and compared with experimental results. In order to ensure the stability of numerical calculations, the discrete viscoelastic stress splitting method (DEVSS)/ streamline-upwind method (SU) were used to introduce an elliptic operator into the momentum equation and suppress the convection dominance for high Weissenberg numbers. An improved finite incremental calculus method (FIC) was introduced to reconstruct the mass conservation equation, so as to apply the pressure stabilized iterative fractional step scheme to solve the velocity, pressure and stress by using the equal low-order interpolation elements. The results show that the extrusion swell ratio, velocity, pressure, stress and backbone stretch distributions predicted by the DCPP and S-MDCPP models agree very well, and the pressure stabilized iterative fractional step scheme and the equal low-order interpolation elements adopted for the S-MDCPP model are reliable. Moreover, two models were also used to predict the extrusion swell ratio and extrusion pressure of linear low-density polyethylene melts at different shear rates. And compared with the experimental results, it is found that at low shear rate, they have the good agreement. © 2021, Editorial Board of Polymer Materials Science & Engineering. All right reserved.