Abstract
Large eddy simulation (LES) of transient magnetohydrodynamic (MHD) turbulent flow under a single-ruler electromagnetic brake (EMBr) in a laboratory-scale, continuous-casting mold is presented. The influence of different electrically-conductive boundary conditions on the MHD flow and electromagnetic field was studied, considering two different wall boundary conditions: insulating and conducting. Both the transient and time-averaged horizontal velocities predicted by the LES model agree well with the measurements of the ultrasound Doppler velocimetry (UDV) probes. Q-criterion was used to visualize the characteristics of the three-dimensional turbulent eddy structure in the mold. The turbulent flow can be suppressed by both configurations of the experiment’s wall (electrically-insulated and conducting walls). The shedding of small-scale vortices due to the Kelvin–Helmholtz instability from the shear at the jet boundary was observed. For the electrically-insulated walls, the flow was more unstable and changed with low-frequency oscillations. However, the time interval of the changeover was flexible. For the electrically-conducting walls, the low-frequency oscillations of the jets were well suppressed; a stable double-roll flow pattern was generated. Electrically-conducting walls can dramatically increase the induced current density and electromagnetic force; hence they contribute to stabilizing the MHD turbulent flow.
Highlights
Continuous casting (CC) has become one of the most important production processes in the steel industry
The primary objective of this work was to study the effect of different electrically-conductive boundary conditions on the transient MHD phenomena and electromagnetic field
For the Large eddy simulation (LES) model, the monitoring data was collected at every time step (0.001 s), so a higher frequency and amplitude were obtained than those of the measurements, which had a frequency of 5 Hz for these measuring sensors [30]
Summary
Continuous casting (CC) has become one of the most important production processes in the steel industry. The molten steel from the ladle flows through the tundish into a mold and freezes against the water-cooled copper mold, forming a solidified shell. The molten steel flows in the mold with intense turbulence, especially along the hot jets that escape from the submerged entry nozzle (SEN) ports. The hot jets are very likely to cause a “breakout” accident near the impingement points on the narrow walls [1]. The turbulent flow of molten steel plays a key role in the slab quality, since it influences the growth of a solid shell, causes slag entrapment, the floatation of bubbles and non-metallic inclusions [2,3,4,5,6]
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