Bubbly Mold Flow In Continuous Slab Casting: Challenges For Numerical Flow Simulations

The impact on the mold flow of inert gas bubbles originating from a gas injection at the top of the SEN is investigated. Results from a physical model using water and air are compared with corresponding numerical flow model results. In numerical models, the bubble velocities are determined by calculating the force equilibrium between buoyancy, drag force and other forces acting on the bubbles. For the observed bubble size in the physical model, the so determined rising velocity of the bubbles is significantly too high in comparison to the water model experiment. Various effects can influence the rising velocity of bubbles. One of them is that the presence of turbulence obviously increases the drag and reduces the rising velocity. Furthermore, it was observed that bubbles influence the turbulence by inducing additional turbulence. Approaches for different bubble effects are analyzed, applied to numerical model simulations and compared to water model results.