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A new experimental facility has been designed and constructed which represents a 1:5.25 model of an industrial 185 t steel ladle. This setup is intended for systematic investigations of complex liquid metal multiphase flows created by gas blowing from the bottom. Two tons of a Sn-40 wt pct Bi alloy are employed as working fluid, its thermophysical properties are very similar to those of liquid steel. The relatively low operating temperatures (T ~ 200 °C) compared to the real industrial process allow the use of powerful measuring techniques for characterizing the behavior of the gas phase and resulting flow regimes. Argon gas is injected through diverse plug systems into a cylindrical fluid vessel which is equipped with a pressure tight lid to achieve low-pressure conditions for vacuum processing. This paper presents first measurements of the gas distribution close to the free liquid metal surface for various gas flow rates, plug positions and types. Moreover, the pressure in the vessel has been varied between 1 mbar and ambient pressure. The experiments provide a copious data base about flow regimes, void fraction, liquid and bubble velocities, and bubble properties, which can be used to provide so far unknown boundary conditions for numerical simulations of various metallurgical reactors such as steelmaking converters or steelmaking ladles.

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.

Today, the numerical simulation of fluid dynamic phenomena (CFD) in steelmaking applications is state of the art. The latest simulation results for the BOF and AOD as well as the thin strip casting process are described. The basic influence of the process parameters, e.g. blowing and stirring rate, vessel dimension, location of top lance, number and arrangement of porous plugs, on the converter melt flow and mixing time is simulated. In the case of thin strip casting, the free melt flow on the moving belt is influenced by an induced electromagnetic field. The respective MHD (magneto-hydrodynamic) is presented.

Transient effects occur during both steady-state casting as well as transient casting, e.g. a ladle change. These effects are caused by transient boundary conditions at the inlet of the tundish. A time-dependent inlet temperature causes a free convection flow during steady-state casting. During transient casting, such as during a ladle change, the mass flow at the inlet is time-dependent and thus a transient flow develops. In general, transient flow is unwanted because transient flow means a change of conditions for the separation of non-metallic particles. The analysis of the flow in the tundish is carried out by numerical as well as physical simulations. In this case experimental investigations are carried out on a water model. The results of laser optical investigations using Laser Doppler Anemometry (LDA) and Particle Image Velocimetry (DPIV) serve as a validation of the numerical results. The numerical results are then used for the investigation of the thermal melt flow. The effects caused by a changing bath level during transient casting (ladle change) are investigated using the Volume-of-Fluid (VoF) model. Beyond this, the interaction between the melt and slag is taken into account, by using the three phase system melt-slag-air. In addition to the classical methods a new zonal approach is introduced in this paper. The integral balance localises high turbulence mixing regions as well as the development and intensity of back flows. The levelling of the momentum flux between the inlet and the outlet can also be described.

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 - LDA, 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.

The present work describes quantitative digital particle image velocimetry measurements of a full-scale water model of a thin slab mold. Different casting speeds and two submerged entry nozzles with one and two outlet ports have been investigated. The flow pattern of the single-port nozzle shows a counterclockwise-rotating double vortex that is nearly steady-state but leads to high stationary surface waves. The flow jets out of the two-port nozzle oscillate and produce a transient flow pattern with low wave amplitudes. The amplitudes for the one-port nozzle show a linear variation with the volumetric flow rate. The experimental results lead to a good interpretation of the flow phenomena and are used to validate steady-state numerical simulations with the commercial program, CFX, on the basis of the Reynolds equations. To describe anisotropic turbulence effects, the Reynolds stress model (RSM) is used for the flat single-port nozzle and the standard k-ɛ model for the mold flow. The calculated mean velocities and wave amplitudes, predicted from pressure distribution at the water surface, are generally in the consensus of the experimental data.

The fluid flow in a continuous casting tundish affects the separation of non-metallic particles and the cleanliness of the steel. Today, laser-optical investigations of water models are state of the art and enable detailed information about the effect of baffles, i. e. dams, weirs and turbo-stoppers, on the flow. In this work 3D-LDA and 2D-DPIV-investigations for different turbo-stoppers in a water model on a scale of 1:1.7 of a 16 t single strand tundish are presented. Three circular turbo-stoppers are investigated. Detailed measurements of the mean velocity and turbulence intensity in the tundish with and without turbo-stopper are shown. With a suitable turbo-stopper geometry the recirculation area in the tundish centre and short-circuit flows along the side walls can be avoided and thus more favourable residence time distributions can be obtained. It is shown that the turbo-stopper produces higher turbulence in the inlet region of the tundish, which is spatially more limited, however, in relation to the flow without turbo-stopper. Thereby a more homogeneous flow is created at the discharge of the tundish with better conditions for the particle separation. The experimental data yield a good understanding of the flow phenomena in a tundish with turbo-stopper and are used as validating criterion for numerical simulations (Fluent 5.5) on the basis of the Reynolds equations. The turbulence modelling is based on a two-equation model (realizable k-e model).

In the paper, a simple and very accurate measurement technique is presented to determine the volumetric or mass flow rate. It is based on the fully-developed turbulent pipe flow, a new analytical universal velocity-profile over the entire pipe section and a single-point measurement. In combination with an optimized straightener this technique has to show minimal pressure loss, very moderate costs and high measuring accuracy compared to LDA-measurements. It is possible to apply the measuring prinicple to nonisothermal gas flows, too.

The flow in continuous casting tundishes is considerably responsible for the flotation of non-metallic inclusions and the quality of steel. Because tests in liquid steel can hardly be performed, water model testing considering the geometric and dynamic similarity laws is often used. Here, quantitative investigations with time and cost expensive laser measurement techniques are possible. The digital particle image velocimetry (DPIV) can be seen as a completion and is an effective method to obtain reliable results. DPIV measurements on a 1:4 scaled model of a single strand tundish are carried out which lead to a good interpretation of the dynamic flow phenomena. The flow separates at the bottom of the tundish and a recirculating region develops. Simultaneously, the jet out of the shroud induces a contra-rotating double vortex and a short circuit flow along the side walls. Furthermore, a decreasing water level in the physical model is investigated to simulate the ladle change. The experimental results are used to validate numerical simulations on the basis of the Reynolds equations. In order to describe the turbulence, a two-equation model (realizable k-e model) is used. The results obtained with this model correspond well with the DPIV data. The basic intention of the present investigations is to transfer the numerical simulation of the water flow to the melt flow in the next step. Thus, a high accuracy of the theoretical results can be guaranteed.

A test facility has been constructed to realistically simulate the flow around a two dimensional car shaped body in a wind tunnel. A moving belt simulator has been employed to generate the relative motion between model and ground. In a first step, the aerodynamic coefficients c L and c D of the model are determined using static pressure and force measurements. LDA-measurements behind the model show the large vortex and turbulence structures of the near and far wake. In a second step, the ambient flow around the model is modified by way of an active flow control which uses the Coanda effect, whereby the base-pressure increases by nearly 50% and the total drag can be reduced by 10%. The recirculating region is completely eliminated. The current work reveals the fundamental physical phenomena of the new method by observing the pressure forces on the model surface as well as the time averaged velocities and turbulence distributions for the near and far wake. A theory resting on this empirical information is developed and provides information about the effectiveness of the blowing method. For this, momentum and energy equations were applied to the flow around the vehicle to enable a validation of the theoretical results using experimental values.