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Introduction
Publications
Publications (296)
In this paper, we present numerical and experimental results on helicity oscillations in a liquid-metal Rayleigh–Bénard convection cell with an aspect ratio of 0.5. While the numerical simulations use the finite volume library OpenFOAM, the experimental results are obtained by means of contactless inductive flow tomography. We find that helicity os...
This paper presents the analysis of particle-laden liquid metal flow around a cylindrical obstacle at different obstacle Reynolds numbers. Particles in liquid metal are imaged using dynamic neutron radiography. We present the results of particle tracking velocimetry of the obstacle wake flow and demonstrate the capabilities to assess both temporal...
Convection of liquid metals drives large natural processes and is important in technical processes. Model experiments are conducted for research purposes where simulations are expensive and the clarification of open questions requires novel flow mapping methods with an increased spatial resolution. In this work, the method of Ultrasound Localizatio...
Electrolysis stands as a pivotal method for environmentally sustainable hydrogen production. However, the formation of gas bubbles during the electrolysis process poses significant challenges by impeding the electrochemical reactions, diminishing cell efficiency, and dramatically increasing energy consumption. Furthermore, the inherent difficulty i...
Electrolysis stands as a pivotal method for environmentally sustainable hydrogen production. However, the formation of gas bubbles during the electrolysis process poses significant challenges by impeding the electrochemical reactions, diminishing cell efficiency, and dramatically increasing energy consumption. Furthermore, the inherent difficulty i...
In Rayleigh–Bénard convection, the size of a flow domain and its aspect ratio $\varGamma$ (a ratio between the spatial length and height of the domain) affect the shape of the large-scale circulation. For some aspect ratios, the flow dynamics includes a three-dimensional oscillatory mode known as a jump rope vortex (JRV); however, the effects of va...
The formation and behavior of gas bubbles is experimentally investigated in a liquid metal downward pipe flow, a configuration that largely corresponds to the situation in a submerged entry nozzle (SEN) in the continuous casting process in steel making. The experimental mockup is operated at room temperature using the ternary alloy GaInSn as model...
In recent years there is an attempt to control the gas stirring intensity in metal-making ladles with the aid of vibration measurements. Understanding better the induced vibrations in two-phase flows can substantially improve the existing models for gas stirring control. In this work, highly sensitive accelerometers were used for the vibration meas...
In this paper we report on an experimental study focusing on the manifestation and dynamics of the large-scale circulation (LSC) in turbulent liquid metal convection. The experiments are performed inside a cylinder of aspect ratio $\varGamma = 0.5$ filled with the ternary alloy GaInSn, which has a Prandtl number of $Pr = 0.03$ . The large-scale flo...
The capabilities of Fiber Bragg Grating (FBG) sensors to measure temperature variations in the bulk of liquid flows were considered. In the first step of our research project, reported in this paper, we investigated to what extent the use of thin glass fibers without encapsulation, which only minimally disturb a flow, can fulfill the requirements f...
DOI:https://doi.org/10.1103/PhysRevLett.131.159901
A novel concept of a measurement technology for the localization and determination of the size of gas bubbles is presented, which is intended to contribute to a further understanding of the dynamics of efficiency-reducing gas bubbles in electrolyzers. A simplified proof-of-concept (POC) model is used to numerically simulate the electric current flo...
We present an image processing algorithm developed for quantitative analysis of directional solidification of metal alloys in thin cells using x-ray imaging. Our methodology allows to identify the fluid volume, fluid channels and cavities, and to separate them from the solidified structures. It also allows morphological analysis within the solid fr...
A novel concept of a measurement technology for the localization and determination of the size of gas bubbles is presented, which is intended to contribute to a further understanding of the dynamics of efficiency-reducing gas bubbles in electrolyzers. A simplified proof-of-concept (POC) model is used to numerically simulate the electric current flo...
Electrolysis is crucial for eco-friendly hydrogen production, but gas bubbles generated during the process hinder reactions, reduce cell efficiency, and increase energy consumption. Additionally, these gas bubbles cause changes in the conductivity inside the cell, resulting in corresponding variations in the induced magnetic field around the cell....
Electrolysis is crucial for eco-friendly hydrogen production, but gas bubbles generated during the process hinder reactions, reduce cell efficiency, and increase energy consumption. Additionally, these gas bubbles cause changes in the conductivity inside the cell, resulting in corresponding variations in the induced magnetic field around the cell....
Vibration measurements were carried out using highly sensitive accelerometers in an experimental ladle integrated into the LIMMCAST ( Li quid M etal M odel for Steel Cast ing) facility at HZDR. The model is operated with liquid Sn–40 wt pctBi alloy at 200 °C, whose physical properties are close to those of molten steel. Three accelerometers were at...
Following several previous European projects (EFR, CP-ESFR and ESFR-SMART), a new project ESFR-SIMPLE has been proposed in response to the HORIZON-EURATOM call on
“Safety of advanced and innovative nuclear designs and fuels”. The new project aims at challenging the Generation IV ESFR (European Sodium Fast Reactor) designed in the ESFR-SMART project...
In Rayleigh-B\'enard convection (RBC), the size of a flow domain and its aspect ratio $\varGamma$ (a ratio between the spatial length and height of the domain) affect the shape of the large-scale circulation (LSC). For some aspect ratios, the flow dynamics include a three-dimensional oscillatory mode known as a jump-rope vortex (JRV), however, the...
We present measurement results for the flow rate of liquid sodium at temperatures up to 700°C that were obtained with a high temperature prototype of an immersed Eddy Current Flow Meter. The experimental campaign was conducted at the SOLTEC-2 sodium loop at KIT. The main objective of the experiments is the high temperature qualification of the Eddy...
Kurzfassung
Mit der kontaktlosen induktiven Strömungstomografie (CIFT) lassen sich Geschwindigkeitsfelder in elektrisch leitfähigen Flüssigkeiten global bestimmen. Kenntnisse über den Strömungszustand in Metallschmelzen sind für industrielle Prozesse, wie das Stranggießen von Stahl, von immenser Bedeutung und können auch in der Grundlagenforschung...
In mineral processing, froth flotation is based on recovering valuable mineral particles by means of the overflowing froth. Industrial-scale froth flotation cells are typically equipped with optical measurement systems, which monitor the bubble sizes and flow velocities at the froth surface. However, the velocity profile of the overflowing froth un...
Heavy-liquid metals (HLMs), such as lead and lead–bismuth eutectic (LBE), are proposed as primary coolants in accelerator driven systems and next-generation fast reactors. In Europe, the reference systems using HLMs are MYRRHA (LBE) and ALFRED (lead). Extensive R&D programs have been established for supporting their detailed design and safety asses...
We present results on the synchronization of the helicity in a liquid-metal Rayleigh–Bénard experiment under the influence of a tide-like electromagnetic forcing with azimuthal wavenumber m = 2. We show that for a critical forcing strength the typical large-scale circulation in the cylindrical vessel of aspect ratio unity is entrained by the period...
We present an image processing algorithm developed for quantitative analysis of directional solidification of metal alloys in thin cells using X-ray imaging. Our methodology allows to identify the fluid volume, fluid channels and cavities, and to separate them from the solidified structures. It also allows morphological analysis within the solid fr...
We present results on the synchronization of the helicity in a liquid-metal Rayleigh-B\'enard (RB) experiment under the influence of a tide-like electromagnetic forcing with azimuthal wavenumber m=2. We show that for a critical forcing strength the typical Large Scale Circulation (LSC) in the cylindrical vessel of aspect ratio unity is entrained by...
This paper presents the analysis of the particle-laden liquid metal wake flow around a cylindrical obstacle at different obstacle Reynolds numbers. Particles in liquid metal are visualized using dynamic neutron radiography. We present the results of particle tracking velocimetry of the obstacle wake flow using an improved version of our image proce...
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...
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 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...
Lack of appropriate flow measurement techniques for liquid steel during continuous casting limits the application of control strategies that could improve the quality of the end product. Contactless Inductive Flow Tomography (CIFT) is a promising measurement technique that can provide information about the flow structure in the mould to a real time...
Contactless inductive flow tomography (CIFT) can reconstruct the complex 3-dimensional flow structure of the large-scale circulation in liquid metal filled Rayleigh-Bénard (RB) convection cells. The method relies on the precise measurement of weak magnetic fields induced by currents in the conducting liquid arising from the fluid motion in combinat...
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...