# Technical theory of numerical simulation for casting filling calculation

Simulating and analyzing the metal flow process during mold filling, the heat transfer phenomenon during mold filling, and the coupling calculation of flow field and temperature field after mold filling are important contents of the numerical simulation of casting process. First of all, by simulating and analyzing the flow state of liquid metal in the gating and riser system and the casting mold, the design of the gating and riser system can be improved to prevent the suction of liquid metal in the runner, eliminate the separation of flow streams to avoid the oxidation of the casting, reduce the turbulence to reduce the possibility of air entering the liquid metal, and use the gating system to block the slag to achieve the uniform distribution of metal flow in multiple transverse and inner runners, To reduce the erosion and impact of liquid metal on the mold, on the other hand, by simulating and analyzing the temperature changes of liquid metal and mold during the filling process, defects such as cold shut and insufficient pouring can be predicted, and the initial temperature field conditions can be provided for the subsequent solidification process simulation analysis.

The model of casting filling process is composed of four independent and interrelated models, These four models are respectively fluid flow model – corresponding to solving the most critical continuity equation and momentum equation; heat transfer model – corresponding to solving the energy equation; free surface model – corresponding to solving the free boundary condition (in the process of casting filling, the free boundary is the free surface where the air and liquid metal contact in the cavity); and turbulence model – corresponding to solving the turbulence equation. In the process of casting filling, in order to fully describe this process, all the above equations need to be solved at the same time. Therefore, the numerical simulation of casting filling process is a multidisciplinary research field, which involves computational fluid dynamics, heat transfer, computer graphics, calculation methods, mathematical theory of partial differential equations and casting technology theory. 