Experimental validation of flow and tracer-dispersion models in a four-strand billet-casting tundish
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I. INTRODUCTION
EXTENSIVE experimental and computational studies on the steelmaking tundish system have been carried out during the past two decades and are reported in the literature. A good deal of these have already been summarized in a review presented by Mazumdar and Guthrie.[1] Many investigations have continued to be reported during the intervening period on a diverse range of topics of relevance to the steelmaking tundish, including fluid flow, residence-time distribution (RTD), inclusion floatation, thermal-energy transport phenomena, etc. In Table I, summary of various studies reported in the open technical literature during the last two and one-half decades and is presented. There, as seen, both physical and mathematical modeling have been applied to investigate transport processes (tracer dispersion, inclusion and thermal-energy transport, etc.). These latter processes are essentially “convection turbulent diffusion processes” and, therefore, depend on the nature of fluid-flow conditions within the system. Thus, the reliability of the prediction of various transport processes would depend on the accuracy of the predicted flow and turbulence parameters. Considerable importance was, therefore, naturally given to the prediction of turbulent-flow fields and, accordingly, the general adequacy of the flow model was assessed by validating computational results against experimental observations. Interestingly, as seen from Table I, direct validation of flows (through particle-image velocimetry (PIV), laser doppler ANIL KUMAR, Graduate Student, and DIPAK MAZUMDAR and SATISH C. KORIA, Professors, are with the Department of Materials and Metallurgical Engineering, Indian Institute of Technology, Kanpur 208 016, India. Contact e-mail: [email protected] Manuscript submitted October 11, 2004. METALLURGICAL AND MATERIALS TRANSACTIONS B
velocimetry (LDV), or similar devices) has been relatively rare. The accuracy of flow models has been assessed by comparing the predicted C curves with experimental ones; matching of both curves was taken to be a sufficient indication of the accuracy of the underlying flow model. This, however, may not be always so, since tracer dispersion (or in fact, any scalar transport process), being a “turbulent convection-diffusion process,” would depend on both the flow as well as the turbulence parameters in the system. Naturally, therefore, it is not entirely unlikely that underprediction of flow coupled with overprediction of turbulence can also lead to realistic estimates, even though flow and turbulence may not be independently, sufficiently accurate. Consequently, in such a context, direct experimental validation of flow and turbulence phenomena appears to be the most reasonable and appropriate approach to assess the adequacy of the flow models. Referring back to Table I, it is readily seen that, despite large number of model studies reported on the tundish system, simultaneous measurement and computation of flows was done only by a limited number of investigators. Furthermore, Table I a
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