Numerical simulation of mold filling in foam reaction injection molding

A numerical simulation of reaction injection molding (RIM) of polymeric foam is developed, using a finite volume method (FVM). In this study we predict mold filling with a variable-density fluid that fills a mold by self-expansion. We deal with two-dimensional, isothermal cases. With the assumptions of ideal mixing and rapid bubble nucleation, the foam is modelled as a continuum with a time-dependent density. The continuum is assumed to be a Newtonian fluid. We develop a pressure-based FVM for unstructured meshes that includes the SIMPLE algorithm with treatment of fluid compressibility. Cell-based, co-located storage is used for all physical variables. To treat the moving interface, an explicit high-resolution interface capturing method is used. Foam flow in a slit is investigated, and the numerical calculations are in good agreement with an approximate analytic solution. For fountain flow in a rectangular cavity, the shape of the flow front is flatter and the traces of the particles are more complicated for an expanding foam than for a constant-density fluid. An example of mold filling by an expanding foam demonstrates the geometric flexibility of the method.