In the capillary flow of molten polymers generated by means of a capillary rheometer, there is a large pressure drop associated with the flow in the entrance and exit regions (Fig, 1). The two excess pressure drops due to entrance and exit effects are known as the excess pressure drop due to end effects, ΔP_(End) (also known as Bagley correction) (1). There have been several efforts to understand this behavior, both experimentally (2) and computationally (3,4). The purely viscous theory based on the power-law or the Carreau model does not work very well due to elastic effects. On the other hand, a proper viscoelastic model must be used, making use of a full Theological characterization of the polymers. The effect of capillary geometry regarding different entrance angles Φ (Fig. la) is another aspect, which may influence the results in an unknown way.
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