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Effect of Electromagnetic Ruler Braking (EMBr) on Transient Turbulent Flow in Continuous Slab Casting using Large Eddy Simulations
R. CHAUDHARY, B.G. THOMAS, and S.P. VANKA
Static electromagnetic braking (EMBr) elds aect greatly the turbulent ow pattern in steel continuous casting, which leads to potential benets such as decreasing ow instability, surface defects, and inclusion entrapment if applied correctly. To gain a fundamental understanding of how EMBr aects transient turbulent ow, the current work applies large eddy simulations (LES) to investigate the eect of three EMBr ruler brake congurations on transient turbulent ow through the bifurcated nozzle and mold of a liquid-metal GaInSn model of a typical steel slab-casting process, but with deep nozzle submergence and insulated walls with no solidifying shell. The LES calculations are performed using an in-house graphic-processing-unit-based computational-uid-dynamics code (LES-CU-FLOW) on a mesh of ~7 million brick cells. The
LES model is validated rst via ultrasonic velocimetry measurements in this system. It is then applied to quantify the mean and instantaneous ow structures, Reynolds stresses, turbulent kinetic energy and its budgets, and proper orthogonal modes of four cases. Positioning the strongest part of the ruler magnetic eld over the nozzle bottom suppresses turbulence in this region, thus reducing nozzle well swirl and its alternation. This process leads to strong and focused jets entering the mold cavity making large-scale and low-frequency (<0.02 Hz) ow variations in the mold with detrimental surface velocity variations. Lowering the ruler below nozzle deects the jets upward, leading to faster surface velocities than the other cases. The double-ruler and no-EMBr cases have the most stable ow. The magnetic eld generates large-scale vortical structures tending toward two-dimensional (2-D) turbulence. To avoid detrimental large-scale, low-frequency ow variations, it is recommended to avoid strong magnetic elds across the nozzle well and port regions.
DOI: 10.1007/s11663-012-9634-6 The Minerals, Metals & Materials Society and ASM International 2012
I. INTRODUCTION
ELECTROMAGNETIC braking (EMBr) is an ecient and nonintrusive way to control the turbulent ow pattern and its stability in the nozzle and the mold region of the continuous casting process for steel slabs. Turbulent ow in this process is the main cause of expensive defects, including surface quality, internal quality, and inclusion-related defects. As explained in more detail elsewhere,[1,2] surface defects caused by meniscus...