Sven Eckert

Helmholtz-Zentrum Dresden-Rossendorf | HZDR · Institute of Fluid Dynamics

The size and shape of the primary dendrite tips determine the principal length scale of the microstructure evolving during solidification of alloys. In-situ X-ray measurements of the tip shape in metals have been unsuccessful so far due to insufficient spatial resolution or high image noise. To overcome these limitations, high-resolution synchrotro...

This paper demonstrates particle tracking velocimetry performed for a model system wherein particle-laden liquid metal flow around a cylindrical obstacle was studied. We present the image processing methodology developed for particle detection in images with disparate and often low signal- and contrast-to-noise ratios, and the application of our MH...

Flow control of liquid metals based on the actual flow condition is important in many metallurgical applications. For instance, the liquid steel flow in the mould of a continuous caster strongly influences the product quality. The flow can be modified by an electromagnetic brake (EMBr). However, due to the lack of appropriate flow measurement techn...

Liquid metal convection plays an important role in natural and technical processes. In experimental studies, an instrumentation with a sub-millimeter spatial resolution is required in an opaque fluid to resolve the flow field near the boundary layer. Using ultrasound methods, the trade-off between the frequency and imaging depth of typical laborato...

The large-scale flow structure and the turbulent transfer of heat and momentum are directly measured in highly turbulent liquid metal convection experiments for Rayleigh numbers varied between 4×10^{5} and ≤5×10^{9} and Prandtl numbers of 0.025≤Pr≤0.033. Our measurements are performed in two cylindrical samples of aspect ratios Γ=diameter/height=0....

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...

More than 96% of steel in the world is produced via the method of continuous casting. The flow condition in the mould, where the initial solidification occurs, has a significant impact on the quality of steel products. It is important to have timely, and perhaps automated, control of the flow during casting. This work presents a new concept of usin...

An efficient and versatile implementation of offline multiple hypothesis tracking with Algorithm X for optimal association search was developed using Python. The code is intended for scientific applications that do not require online processing. Directed graph framework is used and multiple scans with progressively increasing time window width are...

The interdependence between structural mechanics and microstructure solidification has been widely observed experimentally as a factor leading to undesirable macroscopic properties and casting defects. Despite this, numerical modelling of microstructure solidification often neglects this interaction and is therefore unable to predict key mechanisms...

Using complementary experiments and direct numerical simulations, we study turbulent thermal convection of a liquid metal (Prandtl number $\textit {Pr}\approx 0.03$ ) in a box-shaped container, where two opposite square sidewalls are heated/cooled. The global response characteristics like the Nusselt number ${\textit {Nu}}$ and the Reynolds number...

We study the topology and the temporal dynamics of turbulent Rayleigh–Bénard convection in a liquid metal with a Prandtl number of 0.03 located inside a box with a square base area and an aspect ratio of $\varGamma = 5$ . Experiments and numerical simulations are focused on the Rayleigh number range $6.7 \times 10^{4} \leqslant Ra \leqslant 3.5 \ti...

The size and shape of the primary dendrite tips determine the principal length scale of the microstructure evolving during solidification of alloys. In-situ X-ray measurements of the tip shape in metals have been unsuccessful so far due to insufficient spatial resolution or high image noise. To overcome these limitations, high-resolution synchrotro...

The large-scale flow structure and the turbulent transfer of heat and momentum are directly measured in highly turbulent liquid metal convection experiments for Rayleigh numbers varied between $4 \times 10^5$ and $\leq 5 \times 10^9$ and Prandtl numbers of $0.025~\leq~Pr~\leq ~0.033$. Our measurements are performed in two cylindrical samples of asp...

We study the topology and the temporal dynamics of turbulent Rayleigh-Benard convection in a liquid metal with a Prandtl number of 0.03 located inside a box with a square base area and an aspect ratio of five. Experiments and numerical simulations are focused on the moderate Rayleigh number range, where a new cellular flow regime has been reported...

This paper demonstrates particle tracking velocimetry performed for a model system wherein particle-laden liquid metal flow about a cylindrical obstacle was studied. We present the image processing methodology developed for particle detection in images with disparate and often low signal- and contrast-to-noise ratios, and the application of our MHT...

Abstract of the presentation for the upcoming STEELSIM-conference in october 2021.

Detailed description of the animated supplementary results for the paper: Vakhrushev, A., Kharicha, A., Karimi-Sibaki, E. et al. Generation of Reverse Meniscus Flow by Applying An Electromagnetic Brake. Metall Mater Trans B (2021). https://doi.org/10.1007/s11663-021-02247-x

Simulation results of the turbulent flow under the applied EMBr of 156 mT showing the distribution of the induced electric current, velocity field and the turbulent structures (defined by the iso-surface Qcrit=100). The flow alternation is significant: turbulence is mostly damped; corresponding redistribution of the linear momentum causes accelerat...

Simulation results of the turbulent flow under the applied EMBr of 441 mT showing the distribution of the induced electric current, velocity field and the turbulent structures (defined by the iso-surface Qcrit=100). The opposite vortex dominates and occupies the upper part of the mold. It is accompanied by strong reverse flow zones above and below...

Simulation results of the turbulent flow under the applied EMBr of 366 mT showing the distribution of the induced electric current, velocity field and the turbulent structures (defined by the iso-surface Qcrit=100). The flow pattern is dramatically changed: the meniscus is deaccelerated; two reverse flow zones are formed above and below the jets; a...

Simulation results of the turbulent flow under the applied EMBr of 39 mT showing the distribution of the induced electric current, velocity field and the turbulent structures (defined by the iso-surface Qcrit=100). The flow is slightly rearranged under the magnetic field; however, no significant change is observed.

A numerical study is presented that deals with the flow in the mold of a continuous slab caster under the influence of a DC magnetic field (electromagnetic brakes (EMBrs)). The arrangement and geometry investigated here is based on a series of previous experimental studies carried out at the mini-LIMMCAST facility at the Helmholtz-Zentrum Dresden-R...

The present study deals with high-speed ultrasonic tomography (UT) as a powerful tool to characterize the behavior of multiphase flows. A major goal of the work is to improve the temporal resolution for the detection of transit flow structures and time-dependent phenomena such as the incidence of rising gas bubbles. A special transducer with a wide...

In metallurgy, gas-liquid two-phase flows are relevant for mixing, degassing and refinement. The reliable prediction of the hydrodynamic performance in gas-stirred ladles is of utmost relevance for optimization and process control. A new experimental facility has been designed and constructed for systematic investigations of gas bubbles rising insi...

The Eddy Current Flow Meter is a reliable and robust inductive sensor for the measurement of flowrates in liquid metal flows. This kind of sensor is usually being used in pipe flows where the flow is mostly parallel to the sensor axis. When this sensor is used as part of the safety instrumentation above the subassemblies in liquid metal cooled fast...

In this study we consider the effect of a horizontal magnetic field on the Rayleigh-Bénard convection in a finite liquid metal layer contained in a cuboid vessel (200×200×40mm3) of aspect ratio Γ=5 . Laboratory experiments are performed for measuring temperature and flow field in the low melting point alloy GaInSn at Prandtl number Pr≈0.03 and in a...

An efficient and versatile implementation of offline multiple hypothesis tracking with Algorithm X for optimal association search was developed using Python. The code is intended for scientific applications that do not require online processing. Directed graph framework is used and multiple scans with progressively increasing time window width are...

In geo- and astrophysics, low Prandtl number convective flows often interact with magnetic fields. Although a static magnetic field acts as a stabilizing force on such flow fields, we find that self-organized convective flow structures reach an optimal state where the heat transport significantly increases and convective velocities reach the theore...

In this study we consider the effect of a horizontal magnetic field on the Rayleigh-B\'enard convection in a finite liquid metal layer contained in a cuboid vessel (200 \times 200 \times 40 mm^3). Laboratory experiments are performed for measuring temperature and flow field in the alloy GaInSn at Prandtl number Pr = 0.03 and in a Rayleigh number ra...

In order to precisely determine the magnesium level in a titanium reduction retort by inductive methods, many interfering influences have to be considered. By using a look-up-table method, the magnesium level can be reliably identified by taking into account the interfering effects of the titanium sponge rings forming at the walls with their unknow...

The effects of applying a 0.2-T transverse magnetic field on a solidifying Ga-25 wt%In alloy have been investigated through a joint experimental and numerical study. The magnetic field introduced significant changes to both the microstructure and the dynamics of escaping high-concentration Ga plumes. Plume migration across the interface was quantif...

Flow regimes of Rayleigh–Bénard convection in a vertical magnetic field - Volume 894 - Till Zürner, Felix Schindler, Tobias Vogt, Sven Eckert, Jörg Schumacher

In the present work, the dynamics of a downward gas injection into a liquid metal bath is studied using a numerical modeling approach, and validated with experimental data. As in a top-submerged-lance (TSL) smelter, gas is injected through the lance into the melt. By this means, the properties of the liquid are closer to the actual industrial proce...

We introduce a complex image processing scheme for the simultaneous application of liquid crystal thermometry (LCT), in addition to the previously established method in Anders et al. (Exp Fluids 60(4):68, 2019. 10.1007/s00348-019-2703-8) for particle tracking velocimetry and particle image velocimetry. This scheme was developed for an experimental...

The effects of a vertical static magnetic field on the flow structure and global transport properties of momentum and heat in liquid metal Rayleigh-B\'enard convection are investigated. Experiments are conducted in a cylindrical convection cell of unity aspect ratio, filled with the alloy GaInSn at a low Prandtl number of $\mathit{Pr}=0.029$. Chang...

In this work, we introduce a novel approach to measure the flow velocity of liquid foam by tracking custom-tailored 3D-printed tracers in X-ray radiography. In contrast to optical observations of foam flow in flat cells, the measurement depth equals 100 mm in the X-ray beam direction. Light-weight tracers of millimetric size and tetrapod-inspired s...

We investigate directional solidification of the melt with solid inclusions by means of a non-invasive imaging technique-neutron radiography. For the first time results have revealed particle trapping in the solidifying melt at macro scale. It is shown that particle solidification in volume can be achieved when liquid and solid phases form a mushy...

The local dynamics of dendritic side arms during the growth stage were studied by in-situ radiography observations at high spatial resolution of better than 1 μm. A flat sample of a Ga–In alloy was solidified top-down applying a vertical temperature gradient. The evolving dendritic microstructure was visualized using synchrotron X-ray imaging at th...

Ultrasonic tomography (UT) is a powerful tool for measuring two-phase flow phenomena because it can be applied to opaque fluids and is easy to use. However, its temporal resolution is not as high as those of other methods, such as capacitance or X-ray tomography. Improving the temporal resolution of UT is essential for evaluating time-dependent phe...

A workshop paper has served as preprint of this article and can be found here: http://publications.crs4.it/pubdocs/2019/MPAFMBFMTFECYGJKRZVBNM19. The current paper describes the Computational Fluid-Dynamics (CFD) modelling of Heavy Liquid Metal (HLM) flows in a pool configuration and in particular how this is approached within the Horizon 2020 SESA...

Flow measurements are performed in a slab model for continuous casting of steel under the influence of a ruler type Electromagnetic Brake (EMBr). The Mini-LIMMCAST facility utilizes the low melting GaInSn alloy for flow modeling. Two-dimensional velocity distributions in the center plane of the rectangular mold with a cross section of \(300 \times...

We present an experimental study on the formation and behavior of a liquid metal bubbly flow arising from a downward gas injection through a top submerged lance (TSL). A visualization of the bubble dynamics was achieved by the X-ray radiography combined with high-speed imaging. The experiments were carried out in a parallelepiped container (144 × 1...

Combined measurements of velocity components and temperature in a turbulent Rayleigh–Bénard convection flow at a low Prandtl number of $Pr=0.029$ and Rayleigh numbers of $10^{6}\leqslant Ra\leqslant 6\times 10^{7}$ are conducted in a series of experiments with durations of more than a thousand free-fall time units. Multiple crossing ultrasound beam...

We present an experimental study on bubble chains ascending in the eutectic GaInSn alloy under the influence of a horizontal magnetic field. Argon gas bubbles are injected through a single nozzle positioned in the middle at the bottom of a flat Plexiglas vessel. Bubble size distribution, shape deformation, velocities, etc. are obtained by post-proc...

Combined measurements of velocity components and temperature in a turbulent Rayleigh-B\'enard convection flow at a low Prandtl number of $\mathit{Pr} = 0.029$ and Rayleigh numbers between $10^6 < \mathit{Ra} < 6 \times 10^7$ are conducted in a series of experiments with durations of more than a thousand free-fall time units. Multiple crossing ultra...

The movement of hydrophobic particles in a rising froth column is investigated. Gadolinium particles are hydrophobized and floated by means of small air bubbles. The generated froth is investigated by neutron imaging. Particles are identified by correlating the resulting radiographs with an artificial template of a typical particle and subsequent s...

Turbulent Rayleigh-Bénard convection was investigated within a liquid metal layer, Prandtl number Pr=0.03, in a square vessel having a moderate aspect ratio, Γ=5. Laboratory experiments were performed at moderate Rayleigh numbers, 7.9×103<Ra<3.5×105. Ultrasonic velocity profiling was used to visualize the spatiotemporal flow structure in two horizo...

A novel masking technique for particle image velocimetry (PIV)-analysis of multiphase flows is presented. With this new approach, the velocity-field of an unmasked particle fraction (e.g., PIV-tracers) can be determined without the influence of a second (masked) particle fraction (e.g., bubbles or solid particles). Starting from a series of segment...

This study focuses on an experimental investigation of the fluid flow in round bloom continuous casting using a 1:3 model of the industrial casting process. A swirling flow nozzle, represented by the specific design of the RHI Magnesita GYRONOZZLE, is used to produce a swirling motion in the cylindrical mold. The test section is integrated into the...

This article presents a novel coupling of numerical techniques that enable three-dimensional convection-driven microstructure simulations to be conducted on practical time scales appropriate for small-size components or experiments. On the microstructure side, the cellular automata method is efficient for relatively large-scale simulations, while t...

Rayleigh-Bénard (RB) convection plays an important role in geo- and astrophysics as well as in many metallurgical applications. At sufficiently high values of the Rayleigh number, a large scale circulation (LSC) is formed whose dynamics had turned out to be surprisingly rich. In this paper, the applicability of the contactless inductive flow tomogr...

Wrought aluminum alloys and in particular extruded products have a large economic importance worldwide. The opportunities to increase the quality or to reduce the production cost have great a strong finance and ecologic incentive. AC magnetic fields provide the possibility to influence the melt flow in a contactless way to influence the temperature...

Electromagnetic actuators are widely used in industry for contactless control of the steel flow in the continuous casting process. However, a real control of the flow structure by those actuators is a challenging task due to the lack of flow monitoring devices. Even a satisfying non real-time characterisation of the melt flow from plant measurement...

In continuous casting, the flow structure of the liquid steel in the mould and the two-phase distribution in the submerged entry nozzle (SEN) are crucial for the quality of the produced steel. In order to effectively control the flow in the mould by electromagnetic brakes (EMBrs) and the injection of gas into the SEN, even a rough knowledge of the...

Experimental results were obtained at the Mini-LIMMCAST facility [1], an experimental setup to model continuous casting of steel operated continuously as a loop with the cold liquid metal alloy GaInSn. The setup consists of a round mould with an inner diameter of 80 mm, representing a mould used in industrial bloom casting in a scale of 1:3. A moul...