Transient free‐surface flows in injection mold filling

Abstract Advancing and colliding flow fronts are important fluid mechanical problems in injection mold filling. These are small‐scale, transient free‐surface flows with a significant impact on the molecular orientation of molded parts. This paper describes a numerical technique for the simulation of transient free‐surface flows. The algorithm combines a Galerkin/finite‐element discretization of the governing equations with a predictor‐corrector scheme for integration in time, and determines simultaneously the flow field and the free surface at every time step. The method is applied to the start‐up of a fluid flow initially at rest and impingement of two flow fronts to form a weldline. Comparison of simulation with available experiments on the start‐up problem shows very good agreement. Numerical tracking of fluid elements clarifies various aspects of flow‐induced deformation of the material.