Verification and validation of openInjMoldSim, an open-source solver to model the filling stage of thermoplastic injection molding

Abstract

In the present study, the simulation of the three-dimensional (3D) non-isothermal, non-Newtonian fluid flow of polymer melts is investigated. In particular, the filling stage of thermoplastic injection molding is numerically studied with a solver implemented in the open-source computational library <inline-formula> <math display="inline"> <semantics> <mrow> <mi>O</mi> <mi>p</mi> <mi>e</mi> <mi>n</mi> <mi>F</mi> <mi>O</mi> <mi>A</mi> <msup> <mi>M</mi> <mi>®</mi> </msup> </mrow> </semantics> </math> </inline-formula>. The numerical method is based on a compressible two-phase flow model, developed following a cell-centered unstructured finite volume discretization scheme, combined with a volume-of-fluid (VOF) technique for the interface capturing. Additionally, the Cross-WLF (Williams–Landel–Ferry) model is used to characterize the rheological behavior of the polymer melts, and the modified Tait equation is used as the equation of state. To verify the numerical implementation, the code predictions are first compared with analytical solutions, for a Newtonian fluid flowing through a cylindrical channel. Subsequently, the melt filling process of a non-Newtonian fluid (Cross-WLF) in a rectangular cavity with a cylindrical insert and in a tensile test specimen are studied. The predicted melt flow front interface and fields (pressure, velocity, and temperature) contours are found to be in good agreement with the reference solutions, obtained with the proprietary software <inline-formula> <math display="inline"> <semantics> <mrow> <mi>M</mi> <mi>o</mi> <mi>l</mi> <mi>d</mi> <mi>e</mi> <mi>x</mi> <mn>3</mn> <msup> <mi>D</mi> <mi>®</mi> </msup> </mrow> </semantics> </math> </inline-formula>. Additionally, the computational effort, measured by the elapsed wall-time of the simulations, is analyzed for both the open-source and proprietary software, and both are found to be similar for the same level of accuracy, when the parallelization capabilities of <inline-formula> <math display="inline"> <semantics> <mrow> <mi>O</mi> <mi>p</mi> <mi>e</mi> <mi>n</mi> <mi>F</mi> <mi>O</mi> <mi>A</mi> <msup> <mi>M</mi> <mi>®</mi> </msup> </mrow> </semantics> </math> </inline-formula> are employed.