Large eddy simulation modelling of asymmetrical flow structures in a vertical-bending continuous caster

Abstract

Transient asymmetric circulations in the vertical-bending section of a continuous caster were simulated using a large eddy simulation (LES) model. The accuracy of the modelling was verified by comparing the jet behaviours, asymmetrical flow structures in the water model, and velocities reported in the literature. Coherent structures play an essential role in the circulations motion in the vertical-bending caster. A classical Q-criterion was introduced to detect and identify coherent vortices to investigate flow structures. The results indicate that coherent vortices in the lower circulation exhibit asymmetrical features, which further reveal the nature of the turbulence behind the flow structures in the caster. Monitoring points were then selected to investigate the motions of the “strong” and “weak” circulatory vortices and corresponding velocity variations at the interface between the vertical and bending section of the caster. The alternative variations show the periodic behaviours of asymmetrical circulations at both sides of the vertical-bending caster. Besides these circulations were interrelated and interacted, they were also affected by the curved section of the caster, which resulted in the asymmetrical flow structures in the vertical-bending caster. Finally, the effects of casting speed and SEN immersion depths on the oscillation frequency of circulations during a continuous casting process were analysed. As the casting speed increased, the oscillation frequency and power spectrum increased accordingly; as the SEN immersion depth increased, the oscillation frequency and power spectrum thereof decreased accordingly.