Numerical study on mould powder entrapment caused by vortexing in a continuous casting process

Unsteady three-dimensional turbulent flow phenomena are seen to have a major impact on steel quality in the continuous casting process. Usually steel mould powder is placed on top of the mould in order to use it as a lubricant between the solidifying steel and the mould and to prevent heat losses from the molten steel. It is well known that mould powder entrapment into the molten steel lowers the quality of the final steel products significantly. This can be caused by a vortexing flow at the interface between mould powder and molten steel near the submerged entry nozzle (SEN). The paper describes a study which was performed to analyse if commercial Computational Fluid Dynamics (CFD) software is capable of predicting the transient build-up of vertical structures in the casting mould. Two-phase-flow phenomena have been modelled by using the Volume Of Fluid (VOF) method. The influence of different turbulence models, mesh densities and initial as well as boundary conditions on the resulting flow field was investigated. Due to the size and complexity of the problems the simulations partially had to be performed in parallel mode on a Linux-cluster computing environment.