Structure of turbulent flow in a slab mold
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NTRODUCTION
STEEL meniscus and its dynamic behavior are a direct consequence of the turbulence structure of a flow in slab molds and are related to the casting speed and design of the submerged entry nozzle (SEN). The fluid-flow structure of the free surface affects directly the first solidification phenomenon at the meniscus and the entrainment rate of flux into the metal bulk. Other phenomena associated with fluidflow structure are vortices formed between the SEN and the narrow face and turbulence-level oscillations at the meniscus, which may lead to strand breakouts and longitudinal cracks in the broad face of a slab.[1] Figure 1 is a scheme[2] of problems related to fluid-flow structure in a mold. The fluidflow structure influenced by gas bubbling through the SEN has been addressed by the authors in other works,[3–6] where it is demonstrated that the presence of gas gives origin to structural-coupled, structural-uncoupled, and transitional flows with radical changes of the fluid-flow patterns. Although fluid flow in slab molds, either with or without gas injection, has been the subject of many articles[7–11] and a review,[12] only few articles are related to the fluidflow structure near and at the meniscus,[13,14,15] either in oneor two-phase flows. In the present work, we focus on the one-phase flow and its structure at and close to the meniscus. Additional interest for one-phase flows in thick-slab molds is due to the existence of still unveiled issues such as the influence of the casting speed on meniscus fluctuations, which should be explained on quantitative grounds in terms PÁVEL RAMÍREZ-LÓPEZ, L.G. DEMEDICES, and O. DÁVILA, Graduate Students, R. SÁNCHEZ-PÉREZ, Researcher, and R.D. MORALES, Professor and K&E Technologies President, are with the Department of Metallurgy and Materials Engineering, National Polytechnic Institute (IPN)ESIQIE, Mexico D.F., CP 07738. Contact e-mail: [email protected] Manuscript submitted February 25, 2005. METALLURGICAL AND MATERIALS TRANSACTIONS B
of casting speed, distribution of the turbulent kinetic energy, and jet characteristics at the ports. Knowledge development regarding these aspects is useful to find and define the link between design characteristics of a SEN and the fluidflow pattern in the mold. In this work, the study of casting-speed effects on fluid-flow structure, meniscus topography, distribution of kinetic energy, and meniscus oscillations are addressed using a water model and mathematical simulations. The final goal of this research is to contribute to the knowledge of turbulence phenomena in continuous-casting molds. II. EXPERIMENTAL To simplify the study, a water-model mold and a submergedentry nozzle (SEN) of fixed dimensions, whose geometric characteristics have been reported in other works,[3–5,6,16] are employed here. Table I resumes the dimensions of this mold and the characteristics of the SEN. Flow fields were recorded using particle-image velocimetry (PIV) equipment, which is described in those works. The steady-state experiments are the same as thos
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