Nawalax Thongjub, Supachara Kongnuan

Abstract: This study investigates pressure tooling issues in Non-Newtonian fluids under both isothermal and non-isothermal conditions, focusing on annular drag flow. The analysis considers creeping pressure tooling flow in a two-dimensional axisymmetric cylindrical coordinate system. These problems are modeled using non-linear partial differential equations derived from the Navier–Stokes, heat transfer, and Oldroyd-B formulations. To solve the governing and constitutive equations, the Semi-implicit Taylor–Galerkin pressure-correction finite element method (STGFEM) is employed. For polymer melt flows at Weissenberg numbers (We), a feedback mechanism is introduced to adjust the inlet boundary conditions. To enhance convergence, the streamline-upwind/Petrov–Galerkin approach is incorporated. Finally, the swelling ratio of the extruded product is compared with experimental data from pressure tooling applications. The computed extrudate dimensions show strong agreement with experimental results and reasonable consistency with analytical predictions. While experimental and numerical outcomes are closely matched, a discrepancy is observed when compared to the analytical model. As a result, non-isothermal systems exhibit greater pressure drop, shear rate, and elongation compared to isothermal cases. Thermal effects weaken the intermolecular bonding in polymers, thereby influencing shear rate and pressure drop. The temperature of pressure-tooling process is very useful to keep the polymeric material from hardening and to support it easier to propel the polymer stream through the die. The maximum temperature is observed at the leading edge of the pressure-tooling domain, after which it decreases progressively and eventually diminishes once the wire becomes coated with the polymer melt in the free-surface region.

Keywords: Isothermal condition, Non-isothermal conditions, Pressure tooling

Date Published: October 18, 2025
DOI: 10.11159/jffhmt.2025.034

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