A Computational Fluid Dynamic (CFD) benchmark for the water model of a single‐strand continuous casting tundish was performed by ten members of the newly founded working group “Fluid Mechanics and Fluid Simulation” of the German Steel Institute VDEh. A critical comparison is drawn between laser‐optical velocity measurements and residence time measurements on the one hand and CFD simulations using different CFD programs, turbulence models, boundary conditions, proposed solutions, etc., on the other hand. The validation criteria used include, among others, the turbulence distribution, the position of the recirculation center and the maximum backflow velocity in the tundish which is induced by the recirculation, as well as the residence time distribution. The results show that the flow and turbulence structure can be computed on the basis of the Unsteady Reynolds averaged Navier‐Stokes (URANS) equations with a good degree of accuracy. The relative positional deviation of the recirculation center is ‐12.5% < Δx/L1 < 5.0%. The characteristic times Θmin, Θmax, Θ20% and Θ5% , which describe the residence time distribution, are established with a variation of ±15%. The benchmark yields important results for the sensible use of today's commonly used numerical CFD models and contributes to further improving the reliability of CFD simulations in metallurgical process engineering.

The exponential growth of computing power in the last two decades opens up entirely new options for numerical simulations of the Electric Arc Furnace (EAF). Simulations can be used to analyze physical phenomena resisting direct observation or operational measurement even to this very day. This paper gives an overview of the state-of-the-art of the Computational Fluid Dynamics (CFD) simulation on the EAF as well as an outlook on future fields of application, while being well aware that by far not all phenomena and literature can be used. The paper makes no claim to exhaustiveness, especially since three subjects of simulation technology have to be excluded: Process models for furnace controlling, stress calculations, electromagnetic simulations. Thus, the focus is on the fluid-and thermo-dynamic furnace processes and on fundamental methods that can be applied to examine these processes. The basic EAF functionalities and selected fluid-dynamic simulations are presented, for example, on multiphase flow, thermal loading of refractory lining and wall panels, chemical reactions and post-combustion, oxygen injection technology, and bottom tapping.

The fluid flow in a continuous casting tundish is numerically and physically simulated by means of water models. Results of residence time distribution (RTD) measurements and laser-optical measurements (Laser Doppler Anemometry -LOA, Digital Particle Image Velocimetry -DPIV) are used to validate the numerical results for water before the numerical simulation is transferred to the steel melt. The investigations are focused on both steady-state and transient casting conditions. To reduce vortexing and turbulence in the tundish different types of turbo-stoppers are installed in the water models and their influence on the spacious flow structure is discussed. The turbo-stopper produces higher turbulence in the inlet region of the tundish, but this region is spatially more limited in relation to the flow without turbo-stopper. Thereby a more homogeneous flow is created at the outlet of the tundish with better conditions for particle separation. Basic design criteria for the geometry of a turbo-stopper are developed. Moreover, the processes of first tundish filling and ladle change are simulated at a downscaled water model and these results are compared with numerical simulations using a Volume of Fluid (VoF) model. This multiphase model is able to reproduce the motion of gas bubbles and waves at the free surface. Numerische und physikalische Simulation vonStromungsphanomenen im StranggieBverteiler. Die Stromung im StranggieBverteiler wird anhand von Wassermodellen numerisch und physikalisch simuliert. Die Ergebnisse von Verweilzeitmessungen (RTD) und laser-optischen Messungen (Laser Doppler Anemometry -LOA, Digital Particle Image Velocimetry -DPIV) werden verwendet, um die numerischen Resultate fiir die Wasserstromung zu validieren. AnschlieBend wird die numerische Simulation auf Stahlschmelzen Obertragen. Die Untersuchungen umfassen sowohl stationii.re als auch instationare GieBbedingungen. Zur Reduzierung der Wirbelbildung und Turbulenz werden verschiedene Turbostopper in die Wassermodelle eingebaut. Der Einfluss des Turbostoppers auf die groBraumige Stromungsstruktur wird diskutiert. Im Einlaufbereich des StranggieBverteilers erzeugt der Turbostopper eine hohere Turbulenz, die jedoch gegenOber dem Fall ohne Turbostopper raumlich starker begrenzt ist. Dadurch wird eine homogenere Stromung im Auslaufbereich mit besseren Abscheidebedingungen fOr nichtmetallische Partikel induziert. Wesentliche Gestaltungsmerkmale fOr die Geometrie eines Turbostoppers werden erortert. Ferner werden der FOllvorgang des StranggieBverteilers und der Pfannenwechsel an einem verkleinerten Wassermodell simuliert. Die Ergebnisse werden mit numerischen Simulationen eines Volume-of-Fluid-Modells (VoF) verglichen. Mit diesem Mehrphasenmodell lassen sich die Bewegungen der Gasblasen und Wellen an der freien Oberflache berechnen. steel research 7 4 (2003) No. 1

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The argon-oxygen-decarburization (AOD) process is a common metallurgical treatment to decarburize high-chromium steel melts using oxygen and inert gas injection through sidewall tuyeres and a toplance. AOD converters are characterized by a fast and efficient decarburization, whereby the oxidation of chromium is reduced compared to treatments for regular steel grades like the LD process. However, lowfrequency oscillations with large amplitudes can occur during the process and influence the converter's structural integrity. The aim of plant engineering is the development of an AOD converter using a vessel design that provides a fast decarburization rate and effective mixing, whereby the oscillation's amplitude and the chromium losses are as low as possible. The oscillation of the vessel is induced by the fluid flow. In this study a numerical model is presented, where the oscillation model is integrated in the CFD (computational fluid dynamics) solver by subroutines. The numerical models for both, fluid flow and vessel oscillation, are validated by experiments carried out with a 1:4 scale water model. In a further step, the numerical models are transferred to the actual AOD process. The results of the simulations are compared to experimental results obtained in plant trials. The numerical model developed in the present study can be used as a tool to design AOD vessels that fulfill the above mentioned criteria to satisfy an efficient, reliable and stable process.