Computational analysis of the extrudate shape of three-dimensional viscoelastic, non-isothermal extrusion flows

A 3D transient non-isothermal finite element code is developed to predict the extrudate shape of viscoelastic fluids emerging from an asymmetric keyhole shaped die. The corner-line method is used to model the movement of the free surfaces. The code is tested using two benchmark problems. First the corner-line method is tested using a trumpet shaped object in a 3D uniaxial extensional flow. Secondly, the implementation of the energy balance and the viscoelastic material behaviour is tested using a non-isothermal pipeflow. For both benchmark problems convergence was obtained, giving confidence that the 3D non-isothermal swell problem is correctly implemented. The influence of shear-thinning, elasticity and temperature on the shape of the extrudate is systematically studied. Results are shown for isothermal flows as well as for non-isothermal flows, with isothermal and non-isothermal die walls. Results for isothermal die walls show increasing extrudate swelling with increasing elasticity and that the swelling opposes extrudate bending. Shear-thinning on the other hand, opposes swelling, which initially promotes bending, but also flattens the asymmetric velocity profile, leading to less extrudate bending for high amounts of shear-thinning. Furthermore, extrudate bending was observed even for purely viscous, isothermal extrudates, suggesting that bending is caused by asymmetry in the viscous stresses. Extrudate swelling can be influenced by the wall temperature of the die and non-isothermal die walls can lead to a change in bending direction.