Flow balancing is the process of changing the geometry of a die in order to achieve a specific geometry for the extrusion profile, whilst minimizing the internal stresses in the material. In order to properly balance the flow in a die, the flow itself must first be accurately described.

Often, Generalized Newtonian Fluid (GNF) models are used to compute the flow profile of polymers above their melting points in the die. These models have the benefit of stability for the numerical process and low computational requirements. The drawback of these models is that extensional effects, which are present in converging flows such as in dies, are neglected.

Recently, the GNF-extended (GNF-X) model has been introduced, providing the stability and low computational requirements of non-viscoelastic models whilst implementing extensional stresses and viscosity. In this research this model is implemented into the ANSYS CFX software employing a Finite Volume Method. This aims to improve the accuracy with which the flow inside the die is described and thus the process of flow balancing. The outcome of this study is a comparison between the GNF and GFN-X models.