Three-dimensional modeling of the flow and the interface surface in a continuous casting mold model
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I. INTRODUCTION
THE flow conditions at the molten steel/slag interface are of significant importance in the continuous steel casting process, affecting both the thermal behavior of the top-surface flux/powder layers and the dissolution of rising impurities by the slag. Moreover, increased casting speeds of liquid steel cause waviness and disturbances at the interface surface, which alter the slag layer thickness and may result in re-entrainment of impurities into the molten steel and in emulsification phenomena. The wave characteristics of the interface are influenced by the size and strength of the flow recirculation zone formed at the meniscus region above the exit of the submerged entry nozzle (SEN), which in turn depends on the nozzle design and exit velocity. The effect of the latter was examined by Gupta and Lahiri[1,2] in a water model of continuous slab caster, and the wave amplitude was found to be proportional to a modified Froude number. A different behavior was observed in the experiments of Keicher and Taylor[3] performed in a water-oil mold model, where the wave height normalized by a Froude number was found to decrease with increasing casting speed. The influence of the immersion depth (ID) was also investigated in this study and found to be more pronounced at lower casting speeds. Several numerical works appear in the literature, aiming at the simulation of the flow field into the mold. However, in most of them, the interface surface was fixed either to a plane level[4,5] or to an experimentally obtained curve,[6] and the surface waves were ignored. The effect of nozzle design on the jet characteristics and on the flow field in the mold was numerically investigated by Najjar et al.,[4] using a finite element methodology and the k-« turbulence model. In a similar study, Hershey et al.[5] compared the numerical
J. ANAGNOSTOPOULOS, Associate Professor, is with the Department of Mechanical Engineering, Technological Education Institute (TEI) of Kozani, 50100 Koila, Kozani, Greece. G. BERGELES, Professor, is with the Department of Mechanical Engineering, Fluids Section, Laboratory of Aerodynamics, National Technical University of Athens (NTUA), 15773 Zografou, Athens, Greece. Manuscript submitted May 4, 1998.
METALLURGICAL AND MATERIALS TRANSACTIONS B
results for the flow pattern in the vicinity of the exit port, using a two-dimensional (2-D) and a 3-D simulation. McDavid and Thomas[6] used a 3-D solution methodology to simulate the steady coupled fluid flow and thermal behavior of the top-surface flux layers in continuous steel slabs casting and to investigate the influence of flow field inside the mold on the temperature distribution and heat removal along the flux. Free top-surface oscillations in a water mold model were studied in detail by Panaras et al.,[7] using the finite volume technique and a 2-D curvilinear mesh continuously adapted to the surface at each time-step of integration. The results show that the free surface wave has a predominant length and frequency and the wave amplitude scal
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