SIMULATION OF AIR ENTRAINMENT IN HIGH PRESSURE DIE CASTING APPLICATIONS

Since the computation of two-phase flow and solidification requires strong coupling, simulation of air entrainment in high pressure die casting applications is a challenge. The effects of surface tension, wetting angle and reduced melt flow due to solidification and air entrainment, as well as compression must be modelled with high precision. To achieve these requirements, a finite-volume method featuring arbitrary polyhedral control volumes is used to solve flow and solidification strongly coupled. The volume-of-fluid approach is applied to capture the phase separation between gas, melt and solid in connection with a high-resolution interface-capturing scheme to obtain sharp interfaces between phases. Melt and air phase are considered to be compressible fluid. To model the resistance of the dendrite network to the melt flow, an additional source term in the momentum equation is implemented. At high fraction solid the flow is stopped completely. This methodology was applied to predict air entrainment in high pressure die castings. Basic flow patterns were validated against casting trials using a simplified geometry, and a first industrial application is reported.