Numerical Simulation of Three‐Dimensional Unsteady Extrudate Swell Through Annular Dies: Effects of Die Core Opening Position and Sag on Parison Formation
Bibliographic record
Abstract
ABSTRACT An efficient Lagrangian finite element method is developed to simulate transient parison formation and extrudate swell of Newtonian and viscoelastic fluids extruded from tapered annular dies. The method incorporates a novel remeshing strategy that preserves the initial numbering of nodes and elements across the full flow domain, enabling accurate tracking of both parison formation and transient free‐surface deformation during the extrusion process. The remeshing algorithm operates by splitting a layer of elements, located on the parison side and adjacent to the die exit, whenever significant deformation occurs in the extrusion direction. This splitting is achieved using the neighboring layer of elements in the die land, which is moved forward to divide the highly deformed parison layer adjacent to the die exit. The remaining elements in the die land are then regularized to maintain a uniform width throughout the extrusion process. The predictive ability of the developed Lagrangian method was assessed using both a diverging capillary annular rheometer die and an industrial diverging annular die geometry. The simulated polymeric material was a high‐density polyethylene (HDPE) resin, whose rheological behavior was modeled using a multi‐mode Phan‐Thien‐Tanner (mPTT) constitutive equation. Numerical simulations of extrudate swell from diverging annular dies showed good agreement with available experimental data, demonstrating the accuracy of the proposed approach. Results from the industrial die geometry analysis showed that the position of the die core opening, or stroke, significantly influences both the parison diameter and deformation during the extrusion process. In particular, for the die geometry and flow conditions studied, a die core opening position ranging from 1 to 10 mm resulted in a substantial reduction in parison diameter, up to 30% for a Newtonian fluid and approximately 3% for a viscoelastic fluid. This reduction was further exacerbated when drawdown or sag effect due to gravity was incorporated into the simulations.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".