Transient fluid flow in a continuous casting tundish during ladle change and steady-state casting

Transient effects occur during both steady-state casting as well as transient casting, e.g. a ladle change. These effects are caused by transient boundary conditions at the inlet of the tundish. A time-dependent inlet temperature causes a free convection flow during steady-state casting. During transient casting, such as during a ladle change, the mass flow at the inlet is time-dependent and thus a transient flow develops. In general, transient flow is unwanted because transient flow means a change of conditions for the separation of non-metallic particles. The analysis of the flow in the tundish is carried out by numerical as well as physical simulations. In this case experimental investigations are carried out on a water model. The results of laser optical investigations using Laser Doppler Anemometry (LDA) and Particle Image Velocimetry (DPIV) serve as a validation of the numerical results. The numerical results are then used for the investigation of the thermal melt flow. The effects caused by a changing bath level during transient casting (ladle change) are investigated using the Volume-of-Fluid (VoF) model. Beyond this, the interaction between the melt and slag is taken into account, by using the three phase system melt-slag-air. In addition to the classical methods a new zonal approach is introduced in this paper. The integral balance localises high turbulence mixing regions as well as the development and intensity of back flows. The levelling of the momentum flux between the inlet and the outlet can also be described.