CFD of Polymer Flow and Melting in a 3D-Printer Nozzle

I built the ANSYS Fluent pipeline and melting/solidification model to study PLA flow, heating, and nozzle design.

ME 378 · Northwestern University · March 2025

I built the core CFD pipeline and melting/solidification model to study how nozzle geometry and heating affect PLA extrusion, with the goal of reducing extrusion pressure while maintaining suitable flow conditions for printing.

What I built:

  • A 2D axisymmetric ANSYS Fluent workflow coupling non-Newtonian flow and heat transfer.
  • Viscosity user-defined functions to capture PLA’s temperature and shear-rate dependence.
  • A melting/solidification model using enthalpy-porosity and temperature-dependent heat capacity to resolve the transition from solid filament to flowing polymer.

Tools: ANSYS Fluent · CFD · viscosity UDFs · enthalpy-porosity modeling

My teammates carried out validation comparisons against published simulations and grid-convergence analysis. My contribution was developing the simulation pipeline and material models used in that work.

Carreau-Yasuda PLA viscosity surface showing dependence on temperature and shear rate
Temperature- and shear-dependent PLA viscosity used in the melting/solidification extension.
Liquid-fraction field showing solid PLA melting as it moves through the heated domain
The liquid-fraction field resolves the solid-to-liquid transition upstream of the nozzle. Figures from the team's final presentation.

Team: Jack Nulisch, Carter Taylor, Garrett Mathesen, and Natasha Van Dam.

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