Assessing The Free Surface Tracking Approach to Simulate Extrudate Swell

The extrudate swell, the geometrical modifications that take place when the flowing material leaves the confined flow inside a channel and moves freely without the restrictions promoted by the walls, is a relevant phenomenon in several polymer processing techniques. For instance, in profile extrusion, the extrudate cross-section is subjected to a number of distortions motivated by the swell, which are very difficult to anticipate, especially for complex geometries. As happens in many industrial processes, numerical modelling might provide useful information to support design tasks, i.e., to allow identifying the best strategy to compensate the changes promoted by the extrudate swell. There are different ways to model free-surface flows, which can be grouped in Interface Tracking (IT) and Interface Capturing (IC) approaches. When dealing with steady state processes, which is the case of profile extrusion, IT is usually the best alternative, since it does not present the problems related to interface diffusion inherent to the IC approaches. OpenFOAM comprises a solver to simulate free-surface flows following an IT approach, which was proposed by Tukovic & Jasak (2008) and Tukovic et al., (2012). This work aims to assess the capability of that solver to simulate the extrudate swell process in profile extrusion, by using the interfaceTrackingFvMesh and interTrackMeshMotion libraries available in OpenFOAM-v1912 to track the free surface movement with a dynamic mesh motion. For this purpose, the data provided by Mitsoulis et al., (2012) on simulating the extrudate swell process of a Newtonian fluid at different Reynolds number flows is considered as the reference for validation. The results computed by the OpenFOAM solver show a very good agreement with the reference data.

ACKNOWLEDGEMENT

The authors would like to acknowledge the funding by FEDER funds through the COMPETE 2020 Programme and National Funds through FCT - Portuguese Foundation for Science and Technology under the projects UIDB/05256/2020- UIDP/05256/2020, TSSiPRO - Technologies for Sustainable and Smart Innovative Products (NORTE-01-0145-FEDER-000015) and FAMEST - Footwear, Advanced Materials, Equipment’s and Software Technologies (POCI-01-0247-FEDER-024529). The authors also acknowledge the support of the computational clusters Search-ON2 (NORTE-07-0162-FEDER-000086) and Minho Advanced Computing Center (MACC).

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