A computational and experimental study on mold filling

Mold filling was studied for vertical, thin, plate-shaped cavities, with the liquid entering via some vertical ingate system connected to the bottom. In this study, sand molds were filled up with molten aluminum and molten cast iron, while water was used to fill up perspex models. The front walls of the sand molds were replaced by glass plates to allow observations of temperature distributions and free-surface behavior of the melt during filling. Computational fluid dynamics (CFD) simulations of the filling process were carried out to study free-surface behavior, velocity patterns, and temperature distributions. Digital particle-image velocimetry (DPIV) was used to validate the computer simulations for water. Generally, visual observations of the molten liquids, CFD simulations, and DPIV results are in good agreement. Combining the three techniques has resulted in a better understanding as to how a plate-shaped cavity is filled up. The behavior of the free surface is different for water and the molten metals. An analysis of surface waves is presented that explains these differences. Current ideas as to the role of the Weber number must be rejected. Rather, instabilities are associated with low values of the Ohnesorge number, with surface tension providing the driving force for surface instabilities and with viscosity as the damping force.