Modelling of non-isothermal melt flows in a four strand delta shaped billet caster tundish validated by water model experiments

Abstract

A mathematical model was developed using ANSYS 12.0 in order to simulate non-isothermal melt flows in a delta shaped four strand billet caster tundish. The fluid inside the tundish considered was water, so that the CFD model could later be validated against water model experiments. The buoyancy term was included in the momentum equation using Boussinesq's approximation. Experiments were performed for both the bare tundish, and the tundish fitted with an impact pad. For the bare tundish, step inputs of 5-15°C hotter fluid resulted in significantly stronger natural convection currents towards the extremities of the tundish. On the other hand, for cases of a tundish fitted with an impact pad, the effect of buoyancy driven flows due to step inputs of hot water, was much less pronounced since the pad itself had a big effect on regulating the fluid flow patterns. Step-down conditions were also simulated, where 10-15 degrees cooler fluid was introduced into a hotter liquid within the tundish. Detailed calculations were performed using the DPM, in order to evaluate the number of inclusions passing through the SENs under such transient conditions. While the step-up conditions facilitated the flotation of inclusions because of upward buoyancy driven flows, the step-down condition generated catastrophic results in terms of liquid metal quality. One third and full scale water model experiments were done to validate the numerical model and it was found that the mathematical predictions were in good agreement with the experimental results. © 2012 ISIJ.