Numerical modelling code based on the finite volume method in unstructured grids

In this work, the implementation employed in the new modeling code is described. It is based on the FVM with on a SIMPLE type scheme suitable for unstructured meshes.Fundação para a Ciência e a Tecnologia (FCT

Development of numerical tools to aid the design of complex geometry profile extrusion dies

The research team of this work is involved since the mid-nineties on the development of computational tools to aid the design of profile extrusion dies. Initially, the numerical code employed was based on structured meshes that limited its application to simple geometries. The work planned in this PhD programme comprises the development of a numerical modelling code able to deal with unstructured meshes and its application on the design of profile extrusion dies comprising complex cross sections. In its current state the numerical code under development is able to model de flow of generalized Newtonian fluids inside flow channels using unstructured meshes. This paper describes briefly the current state of the developed code and illustrates its application in a case study involving the design of a profile extrusion die comprising a complex cross section

On the performance of profile extrusion dies

This work presents a study performed with an in-house 3D numerical modelling code, used to evaluate the sensitivity of extrusion dies, optimized with alternative strategies, to process parameters, such as machining inaccuracies, melt rheology and processing conditions.FC

Design of complex profile extrusion dies through numerical modeling

The achievement of a balanced flow is one of the major tasks encompassed in the design of profile extrusion dies [1]. For this purpose numerical modeling codes may be a very useful aid. The research team involved in this work has been working during the last decade on the development of numerical tools to aid the conception of extrusion dies [1,2]. The design code developed so far carries out the automatic search of a final geometry via an optimization routine coupled with geometry and mesh generators and a 3D computational fluid dynamics (CFD) code based on the finite volume method (FVM). This CFD code is able to model the flow of polymer melts in confined channels, but is inadequate to deal with complex geometries, since it is limited to structured meshes. This work describes the recent efforts made to enlarge the scope of the design procedures, that are currently focused on the development of a modeling code able to deal with unstructured meshes. This code solves the continuity and linear momentum conservation equations, with generalized Newtonian fluids, using a SIMPLE based approach. This paper describes the developed numerical modelling code and its employment in a case study that involves the design of a medical catheter extrusion die, focused on the search of a balanced flow distribution. The results obtained show that the developed numerical code is able to deal with complex geometrical problems, being thus a valuable tool to aid the design of extrusion dies to produce complex profiles.The authors gratefully acknowledge funding from Fundacao para a Ciencia e Tecnologia through the PhD Grant SFRH/BD43632/2008 and FCT (COMPETE Program) under the Projects FCOMP-01-0124 - FEDER-010190 (Ref. PTDC/EME - MFE/102729/2008) and FCOMP-01-0124-FEDER-015126 (Refa. FCT PTDC/EME-MFE/113988/2009), and FEDER, via FCT, under the PEst-C/CTM/LA0025/2011 (Strategic Project - LA 25 - 2011-2012)

Using computational modelling to study extensional rheometry tests for inelastic fluids

The present work focuses on the extensional rheometry test, performed with the Sentmanat extensional rheometer (SER) device, and its main objectives are: (i) to establish the modelling requirements, such as the geometry of the computational domain, initial and boundary conditions, appropriate case setup, and (ii) to investigate the effect of self-induced errors, namely on the sample dimensions and test temperature, on the extensional viscosity obtained through the extensional rheometry tests. The definition of the modelling setup also comprised the selection of the appropriate mesh refinement level to model the process and the conclusion that gravity can be neglected without affecting the numerical predictions. The subsequent study allowed us to conclude that the errors on the sample dimensions have similar effects, originating differences on the extensional viscosity proportional to the induced variations. On the other hand, errors of a similar order of magnitude on the test temperature promote a significant difference in the predicted extensional viscosity.This work was funded by FEDER funds through the COMPETE 2020 Program and National Funds through FCT-Portuguese Foundation for Science and Technology under the projects UIDB/05256/2020/, UIDP/05256/2020, CPCA/A2/6202/2020, CPCA_A2_6231_2020, NORTE-08-5369- FSE-000034, under program IMPULSE-Polímeros e Compósitos: Drivers da Inovação Tecnológica e da Competitividade Industrial

Prototype and methodology for the characterization of the polymer-calibrator interface heat transfer coefficient

The extrusion of technical thermoplastics profiles generally uses a dry calibration/cooling system, composed by one or several calibrators in series. One of the major difficulties to be faced when modelling this important stage is an adequate prescription of the heat transfer coefficient, hinterface, between the plastic profile surface and the cooling medium, which must include the effect of the interface contact resistance. This is the motivation that led the present research team to develop a prototype calibration system and respective methodology for the characterization of hinterface values which is able to consider a variety of conditions that can be found in extrusion practice. A modular construction was adopted for the calibration system, which allows studying easily the effect of several process parameters. In this work, the developed prototype system is described and its use is illustrated in the determination of hinterface for the production of a polystyrene tape, under specific processing conditions.The authors gratefully acknowledge funding from Fundacao para a Ciencia e a Tecnologia, FCT (COMPETE Program) under the projects FCOMP-01-0124 - FEDER-010190 (Ref. PTDC/EME - MFE1102729/2008) and FCOMP-01-0124 - FEDER-015126 (Ref. FCT PEst-EME-MFE/113988/2009), and FEDER, via FCT, under the PEstC/CTM/LA0025/2011 (Strategic Project - LA 25 - 2011-2012)