Three-dimensional simulations of non-isothermal transient flow and flow-induced stresses during the viscoelastic fluid filling process

Abstract

The three-dimensional (3D) viscoelastic polymer melt filling process in injection molding has always been regarded as a challenging two-phase flow problem. Numerical investigations concerning it are very limited, especially under the non-isothermal condition. Thus, this article presents a 3D non-isothermal two-phase model to investigate the flow-induced stresses during the viscoelastic fluid filling process. The viscoelastic behavior of polymer melt is predicted by the eXtended Pom–Pom (XPP) model, in which the temperature dependence of polymeric viscosity and relaxation times are described using the Arrhenius equation. The 3D governing equations are solved by a collocated finite volume method. The high resolution revised level set method coupled with a domain extension technique is extended to capture the 3D melt front interface in an irregular cavity. The collocated finite volume method and the revised level set solver are respectively validated using the XPP melts past a cylinder and the single vortex flow. Then the ability of the presented 3D two-phase model is verified by the isothermal Newtonian fluid filling process in a thin rectangular cavity. The numerical results are in good agreement with those reported in literature. Finally, the challenging problem of non-isothermal XPP fluid filling process in a 3D rectangular cavity with one cylindrical insert is investigated. The temperature field, flow-induced stresses and the corresponding rheological behaviors of polymer melt during 3D filling process are quantitatively predicted. Especially, the effects of processing conditions and energy source term on the two normal stress differences are discussed. It is found that melt temperature and injection velocity are the main factors that affect the normal stress differences. The obtained results should be helpful for improving the product properties in practical production.