Modeling 3D viscoelastic secondary flows in extrusion.

摘要

Two numerical techniques were successfully applied to capture viscoelastic flows and were used to model flows during extrusion. The Radial Functions Method (RFM) was implemented to simulate flow patterns in two dimensions (2D) and three dimensions (3D), and correctly predicts secondary flows in fully developed non-circular ducts [34].;Validation was completed to implement a newly developed viscoelastic solver supplied by Favero et al. [42]. Numerical simulations of 2D viscoelastic entry flows were performed using a Finite Volume Method (FVM) with a stress-splitting technique. A planar abrupt contraction was chosen as the test geometry and numerical results were compared with past experimental and other numerical simulation results using a Giesekus model. Limits of stability were inspected where Weissenberg numbers on the order of 240 were successfully simulated. The single and multi-mode Phan-Thien Tanner (PTT) shear-thinning models were then implemented to reproduce full 3D flows through a planar abrupt contraction. Results obtained within this work show excellent qualitative agreement with experimental observations made by Quinzani et al. [85] and simulation results of Azaiez et al. [6]. Comparison studies with work by other researchers, for both a 2D and 3D geometry with aspect ratios up to 10, were also found to be in agreement.;As part of this work, viscoelastic secondary flows in a 3D non-circular duct were simulated using a FVM approach. Single and multi-mode Giesekus and linear-PTT models were implemented. Results are in agreement with experiments [38] as well as numerical results using RFM and FEM [112]. This is an important step toward modeling and simulating flow in an extruder channel. Exploratory FVM simulations were carried out beginning from an unwrapped screw channel to a full 3D single screw under isothermal conditions. The shear thinning characteristics of the Giesekus model were able to capture the polymer's relaxation time under high Weissenberg conditions.