Advances on Viscoelastic Fluid Flow Simulation

The increasing necessity for use of synthetic polymer products, such as for production of packaging, parts of appliances, electronics, cars, biomaterials for medical applications, etc., has led to the polymer industry to seek reduction of waste and increase product quality and productivity. Consequently, a better understanding of how the rheological properties of polymers affect their processing and final product quality is of great importance. In order to obtain faster results with less cost, the studies of modeling and simulation of polymer processing are increasing every day. This chapter aims to describe new tools for CFD simulations of viscoelastic fluids, implemented in the OpenFOAM CFD package due to advantages offered by this software, such as the possibility to use multigrid techniques and data processing parallelization, besides being a free software and open source. The constitutive models of Maxwell, UCM, Oldroyd-B, White-Metzner, Giesekus, Leonov, FENE-P, FENE-CR, linear and exponential PTT, Pom-Pom, XPP and DCPP were included in the general multimode form. In order to validate the developed solver, comparisons with numerical and experimental results from literature were carried out. The results were satisfactory giving credibility to the implemented solver and ensure the availability of a powerful tool for the study of viscoelastic fluids to be used both in academia and in industry. An extension of this tool, used for analysis of free-surface viscoelastic fluid flows using the VOF methodology, is also presented. The die swell experiment, a classical flow phenomenon used in the rheology literature to present the concept of viscoelastic effects, was also simulated. The results obtained using Giesekus model showed the great potential of the developed formulation, once all phenomena observed experimentally were reproduced in the simulations.

Keywords: Viscoelastic fluids, free surface flow, two-phase flow, finite volumes, multimode simulation, die swell simulation, differential constitutive equations, high weissenberg numbers, VOF, CFD, DEVSS, OpenFOAM^TM.