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Frosin, C., Glaser, B., Rangavittal, B. V., Vynnycky, M. & et al., . (2024). Exploring the potential of muon radiography for blast furnace assessments: advancements in non-invasive imaging and structural analysis. Journal of Instrumentation, 19(2), Article ID C02041.
Open this publication in new window or tab >>Exploring the potential of muon radiography for blast furnace assessments: advancements in non-invasive imaging and structural analysis
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2024 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 19, no 2, article id C02041Article in journal (Refereed) Published
Abstract [en]

The BLEMAB European project (BLast furnace stack density Estimation through online Muon ABsorption measurements), the evolution of the previous Mu-Blast European project, is designed to investigate in detail the capability of muon radiography techniques applied to the imaging of the inner zone of a blast furnace. In particular, the goal of this collaboration is to characterize the internal region (so-called cohesive zone) where the slowly downward-moving material begins to soften and melt, which plays an important role in the performance of the blast furnace itself. In this contribution, we describe the state-of-the-art of the muon tracking system which is currently being developed and installed at a blast furnace on the ArcelorMittal site in Bremen (Germany). Moreover, we will present the GEANT4 simulation framework devised for this application together with the simulation results. Finally, we will show the possible contribution of multiple scattering effects to such peculiar applications.

Place, publisher, year, edition, pages
IOP Publishing, 2024
Keywords
Detector design and construction technologies and materials, Particle tracking detectors (Solid-state detectors), Scintillators and scintillating fibres and light guides, Simulation methods and programs
National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:kth:diva-344183 (URN)10.1088/1748-0221/19/02/C02041 (DOI)2-s2.0-85186143709 (Scopus ID)
Note

QC 20240307

Available from: 2024-03-06 Created: 2024-03-06 Last updated: 2024-03-07Bibliographically approved
Vynnycky, M., Rangavittal, B. V. & Glaser, B. (2023). An asymptotic model for gas-solid flow in a countercurrent moving bed reactor. SIAM Journal on Applied Mathematics, 83(2), 882-908
Open this publication in new window or tab >>An asymptotic model for gas-solid flow in a countercurrent moving bed reactor
2023 (English)In: SIAM Journal on Applied Mathematics, ISSN 0036-1399, E-ISSN 1095-712X, Vol. 83, no 2, p. 882-908Article in journal (Refereed) Published
Abstract [en]

Asymptotic methods are employed to analyze earlier two-phase steady-state Euler-Euler models that were originally intended as simplified representations for gas-solid flow in an ironmaking blast furnace; more generally, however, they can be thought of as models for two-phase flow in countercurrent moving bed reactors. A scaling analysis, based around the fact that the solid velocity is typically several orders of magnitude smaller than the gas velocity, indicates that the effects of viscosity and inertia are basically negligible compared with those of gravity and interphase momentum transfer. The resulting reduced model yields quasi-analytical expressions for the solid fraction and the gas velocity, with the former being directly related to the shapes of the reactor and any stagnant zone that may form as a consequence of solids or granular materials being able to withstand substantial amounts of shear; in ironmaking blast furnaces, this occurs near the bottom of the reactor, and the zone is commonly known as the deadman. On the other hand, the solid velocity can be found via a numerical solution of Laplace’s equation; nevertheless, the solution is different to that obtained from earlier potential flow models in blast furnace modeling. Most significantly, the current model would form the basis of a computationally efficient approach for modeling transient heat and mass transfer with chemical reactions in a countercurrent moving bed reactor.

Place, publisher, year, edition, pages
Society for Industrial & Applied Mathematics (SIAM), 2023
Keywords
asymptotics, Euler-Euler model, two-phase flow
National Category
Energy Engineering Other Mathematics
Identifiers
urn:nbn:se:kth:diva-331554 (URN)10.1137/22M1496293 (DOI)001019546500009 ()2-s2.0-85159765956 (Scopus ID)
Note

QC 20230711

Available from: 2023-07-11 Created: 2023-07-11 Last updated: 2023-07-22Bibliographically approved
Vynnycky, M., Safavi Nick, A. & Assuncao, M. (2022). Fast computation of the Lorentz force induced by longitudinal electromagnetic stirring. Journal of Computational and Applied Mathematics, 416, Article ID 114565.
Open this publication in new window or tab >>Fast computation of the Lorentz force induced by longitudinal electromagnetic stirring
2022 (English)In: Journal of Computational and Applied Mathematics, ISSN 0377-0427, E-ISSN 1879-1778, Vol. 416, article id 114565Article in journal (Refereed) Published
Abstract [en]

In this work, we revisit a recent transient three-dimensional (3D) model for longitudinal electromagnetic stirring in the continuous casting of rectangular steel blooms. Whereas the earlier work was able to demonstrate accurate approximations to the solutions in two asymptotic limits, both of which gave economical alternatives to time-consuming 3D computations, here we show that the original governing equations can be manipulated to a form that allows for rapid computation even outside of these asymptotic limits. The resulting formulation requires the numerical solution of two steady-state complex Helmholtz-like equations in two dimensions that are coupled via a non-standard internal interface condition that is reminiscent of that occurring in the study of Marangoni convection; these equations are then solved numerically using the finite-element software Comsol Multiphysics. With this formulation, it is possible to compute the time-averaged Lorentz force components in a way that requires around four orders of magnitude less computational time than the fully 3D approach.

Place, publisher, year, edition, pages
Elsevier BV, 2022
Keywords
Electromagnetic stirring, Maxwell equations, Continuous casting
National Category
Computational Mathematics Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-316122 (URN)10.1016/j.cam.2022.114565 (DOI)000830982800003 ()2-s2.0-85134431252 (Scopus ID)
Note

QC 20220810

Available from: 2022-08-10 Created: 2022-08-10 Last updated: 2022-08-10Bibliographically approved
Vynnycky, M. (2022). On the local solute redistribution equation of macrosegregation, remelting and the formation of channel segregates. International Journal of Heat and Mass Transfer, 190, Article ID 122737.
Open this publication in new window or tab >>On the local solute redistribution equation of macrosegregation, remelting and the formation of channel segregates
2022 (English)In: International Journal of Heat and Mass Transfer, ISSN 0017-9310, E-ISSN 1879-2189, Vol. 190, article id 122737Article in journal (Refereed) Published
Abstract [en]

In this paper, we reassess the local solute redistribution equation (LSRE) of macrosegregation which, since it first appeared in 1960s, has served as a cornerstone for understanding the composition variations that occur in the solidification of alloys. We highlight some anomalies in earlier literature, in particular as regards the prediction of remelting as a precursor to the formation of channel segregates (freckles, A-segregates and V-segregates) in casting processes. Also, we suggest extensions to the LSRE for situations where solute diffusion in the solid phase is not negligible, as well as when the mode of solidification is unconsolidated equiaxed dendritic, rather than columnar/consolidated equiaxed dendritic. In addition, the significance of the equation for latter-day numerical computations of macrosegregation is also discussed.

Place, publisher, year, edition, pages
Elsevier BV, 2022
Keywords
Alloy solidification, Macrosegregation, Remelting, Channel segregates
National Category
Transport Systems and Logistics Environmental Sciences Philosophy
Identifiers
urn:nbn:se:kth:diva-313039 (URN)10.1016/j.ijheatmasstransfer.2022.122737 (DOI)000794042900006 ()2-s2.0-85126545197 (Scopus ID)
Note

QC 20220531

Available from: 2022-05-31 Created: 2022-05-31 Last updated: 2022-06-25Bibliographically approved
Safavi Nick, A., Vynnycky, M. & Jönsson, P. G. (2021). Analysis of a model for longitudinal electromagnetic stirring in the continuous casting of steel. International journal of applied electromagnetics and mechanics, 66(1), 35-61
Open this publication in new window or tab >>Analysis of a model for longitudinal electromagnetic stirring in the continuous casting of steel
2021 (English)In: International journal of applied electromagnetics and mechanics, ISSN 1383-5416, E-ISSN 1875-8800, Vol. 66, no 1, p. 35-61Article in journal (Refereed) Published
Abstract [en]

A recent three-dimensional (3D) model that revisited earlier theoretical work for longitudinal electromagnetic stirring in the continuous casting of steel blooms is analyzed further to explore how the bloom width interacts with the pole pitch of the stirrer to affect the magnetic flux density. Whereas the first work indicated the presence of a boundary layer in the steel near the interface with the stirrer, with all three components of the magnetic flux density vector being coupled to each other, in the analysis presented here we find that the component along the direction of the travelling wave decouples from those in the other two directions and can even be determined analytically in the form of a series solution. Moreover, it is found that the remaining two components can be found via a two-dimensional computation, but that it is not possible in general to determine these components without taking into account the surrounding air. The validity of the asymptotically reduced model solution is confirmed by comparing it with the results of 3D numerical computations. Moreover, the asymptotic approach provides a way to compute the time-averaged Lorentz force components that requires two orders of magnitude less computational time than the fully 3D approach.

Place, publisher, year, edition, pages
IOS Press, 2021
Keywords
Asymptotic analysis, continuous casting, electromagnetic stirring
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-296452 (URN)10.3233/JAE-200010 (DOI)000648879900003 ()2-s2.0-85105750278 (Scopus ID)
Note

QC 20210608

Available from: 2021-06-08 Created: 2021-06-08 Last updated: 2022-06-25Bibliographically approved
Kohlstädt, S., Vynnycky, M., Goeke, S. & Gebauer-Teichmann, A. (2021). On determining the critical velocity in the shot sleeve of a high-pressure die casting machine using open source cfd. Fluids, 6(11), Article ID 386.
Open this publication in new window or tab >>On determining the critical velocity in the shot sleeve of a high-pressure die casting machine using open source cfd
2021 (English)In: Fluids, E-ISSN 2311-5521, Vol. 6, no 11, article id 386Article in journal (Refereed) Published
Abstract [en]

This paper investigates the critical plunger velocity in high-pressure die casting during the slow phase of the piston motion and how it can be determined with computational fluid dynamics (CFD) in open source software. The melt-air system is modelled via an Eulerian volume-of-fluid approach, treating the air as a compressible perfect gas. The turbulence is treated via a Reynolds-averaged Navier Stokes (RANS) approach that uses the Menter SST k-ω model. Two different strategies for mesh motion are presented and compared against each other. The solver is validated via analytical models and empirical data. A method is then presented to determine the optimal velocity using a two-dimensional (2D) mesh. As a second step, it is then discussed how the results are in line with those obtained for an actual, industrially relevant, three-dimensional (3D) geometry that also includes the ingate system of the die.

Place, publisher, year, edition, pages
MDPI AG, 2021
Keywords
Compressible two-phase flow, Critical velocity, High-pressure die casting, OpenFOAM, Shot sleeve
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-312843 (URN)10.3390/fluids6110386 (DOI)000913018000001 ()2-s2.0-85118128383 (Scopus ID)
Note

QC 20220524

Available from: 2022-05-24 Created: 2022-05-24 Last updated: 2023-09-21Bibliographically approved
Kohlstädt, S., Vynnycky, M. & Goeke, S. (2021). On the CFD Modelling of Slamming of the Metal Melt in High-Pressure Die Casting Involving Lost Cores. Metals, 11(1), Article ID 78.
Open this publication in new window or tab >>On the CFD Modelling of Slamming of the Metal Melt in High-Pressure Die Casting Involving Lost Cores
2021 (English)In: Metals, ISSN 2075-4701, Vol. 11, no 1, article id 78Article in journal (Refereed) Published
Abstract [en]

This paper uses computational fluid dynamics (CFD), in the form of the OpenFOAM software package, to investigate the forces on the salt core in high-pressure die casting (HPDC) when being exposed to the impact of the inflowing melt in the die filling stage, with particular respect to the moment of first impact-commonly known as slamming. The melt-air system is modelled via an Eulerian volume-of-fluid approach, treating the air as a compressible perfect gas. The turbulence is treated via a Reynolds-averaged Navier Stokes (RANS) approach. The RNG k-epsilon and the Menter SST k-omega models are both evaluated, with the use of the latter ultimately being adopted for batch computations. A study of the effect of the Courant number, with a view to establishing mesh independence, indicates that meshes which are finer, and time steps that are smaller, than those previously employed for HPDC simulations are required to capture the effect of slamming on the core properly, with respect to existing analytical models and empirical measurements. As a second step, it is then discussed what response should be expected when this force, with its spike-like morphology and small force-time integral, impacts the core. It is found that the displacement of the core due to the spike in the force is so small that, even though the force is high in value, the bending stress inside the core remains below the critical limit for fracture. It can therefore be concluded that, when assuming homogeneous crack-free material conditions, the spike in the force is not failure-critical.

Place, publisher, year, edition, pages
MDPI, 2021
Keywords
compressible two-phase flow, slamming, OpenFOAM, high-pressure die casting, lost salt cores, solid continuum mechanics
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-289898 (URN)10.3390/met11010078 (DOI)000610486300001 ()2-s2.0-85099051722 (Scopus ID)
Note

QC 20210212

Available from: 2021-02-12 Created: 2021-02-12 Last updated: 2022-06-25Bibliographically approved
Reddy, G. M., Seitenfuss, A. B., Medeiros, D. d., Meacci, L., Assuncao, M. & Vynnycky, M. (2020). A Compact FEM Implementation for Parabolic Integro-Differential Equations in 2D. Algorithms, 13(10), Article ID 242.
Open this publication in new window or tab >>A Compact FEM Implementation for Parabolic Integro-Differential Equations in 2D
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2020 (English)In: Algorithms, E-ISSN 1999-4893, Vol. 13, no 10, article id 242Article in journal (Refereed) Published
Abstract [en]

Although two-dimensional (2D) parabolic integro-differential equations (PIDEs) arise in many physical contexts, there is no generally available software that is able to solve them numerically. To remedy this situation, in this article, we provide a compact implementation for solving 2D PIDEs using the finite element method (FEM) on unstructured grids. Piecewise linear finite element spaces on triangles are used for the space discretization, whereas the time discretization is based on the backward-Euler and the Crank-Nicolson methods. The quadrature rules for discretizing the Volterra integral term are chosen so as to be consistent with the time-stepping schemes; a more efficient version of the implementation that uses a vectorization technique in the assembly process is also presented. The compactness of the approach is demonstrated using the software Matrix Laboratory (MATLAB). The efficiency is demonstrated via a numerical example on an L-shaped domain, for which a comparison is possible against the commercially available finite element software COMSOL Multiphysics. Moreover, further consideration indicates that COMSOL Multiphysics cannot be directly applied to 2D PIDEs containing more complex kernels in the Volterra integral term, whereas our method can. Consequently, the subroutines we present constitute a valuable open and validated resource for solving more general 2D PIDEs.

Place, publisher, year, edition, pages
MDPI, 2020
Keywords
parabolic integro-differential equations, backward-Euler, Crank-Nicolson, quadrature rules, Volterra integral term
National Category
Computational Mathematics
Identifiers
urn:nbn:se:kth:diva-286233 (URN)10.3390/a13100242 (DOI)000584199400001 ()2-s2.0-85092482803 (Scopus ID)
Note

QC 20201124

Available from: 2020-11-24 Created: 2020-11-24 Last updated: 2023-03-29Bibliographically approved
Devine, K. M., Vynnycky, M., Mitchell, S. L. & O'Brien, S. B. (2020). Analysis of a model for the formation of fold-type oscillation marks in the continuous casting of steel. IMA Journal of Applied Mathematics, 85(3), 385-420
Open this publication in new window or tab >>Analysis of a model for the formation of fold-type oscillation marks in the continuous casting of steel
2020 (English)In: IMA Journal of Applied Mathematics, ISSN 0272-4960, E-ISSN 1464-3634, Vol. 85, no 3, p. 385-420Article in journal (Refereed) Published
Abstract [en]

This paper investigates the different possible behaviours of a recent asymptotic model for oscillation-mark formation in the continuous casting of steel, with particular focus on how the results obtained vary when the heat transfer coefficient (R-mf), the thermal resistance (mu(f)) and the dependence of the viscosity of the flux powder as a function of temperature, are changed. It turns out that three different outcomes are possible: (I) the flux remains in molten state and no solid flux ever forms; (II) both molten and solid flux are present, and the profile of the oscillation mark is continuous with respect to the space variable in the casting direction; (III) both molten and solid flux are present, and the profile of the oscillation mark is discontinuous with respect to the space variable in the casting direction. Although (I) gave good agreement with experimental data, it suffered the drawback that solid flux is typically observed during actual continuous casting; this has been rectified in this work via alternative (II). On the other hand, alternative (III) can occur as a result of hysteresis-type phenomenon that is encountered in other flows that involve temperature-dependent viscosity; in the present case, this manifests itself via the possibility of multiple states for the oscillation-mark profile at the instants in time when solid flux begins to form and when it ceases to form.

Place, publisher, year, edition, pages
Oxford University Press (OUP), 2020
Keywords
continuous casting, oscillation marks, asymptotic analysis
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-276882 (URN)10.1093/imamat/hxaa010 (DOI)000537515600003 ()2-s2.0-85087440393 (Scopus ID)
Note

QC 20200623

Available from: 2020-06-23 Created: 2020-06-23 Last updated: 2022-06-26Bibliographically approved
Safavi Nick, A. & Vynnycky, M. (2020). On longitudinal electromagnetic stirringing the continuous casting of steel blooms. Journal of Engineering Mathematics
Open this publication in new window or tab >>On longitudinal electromagnetic stirringing the continuous casting of steel blooms
2020 (English)In: Journal of Engineering Mathematics, ISSN 0022-0833, E-ISSN 1573-2703Article in journal (Refereed) Published
Abstract [en]

Recent work highlighting an anomaly in the modelling of rotary electromagnetic stirring (EMS) in the continuous casting of round steel billets is extended to the case of longitudinal stirring for rectangular blooms. An earlier, still often-cited, model forms the basis of the current analysis, which uses asymptotic methods on the three-dimensional (3D) Maxwell equations and demonstrates how the earlier result for the components of the Lorentz force is but a particular case of a more general form. Time-dependent 3D computations using finite-element methods are also performed to verify the validity of the asymptotic analysis, and the relevance of the results to modulated EMS is noted.

National Category
Metallurgy and Metallic Materials Mathematical Analysis
Identifiers
urn:nbn:se:kth:diva-271220 (URN)10.1007/s10665-019-10035-5 (DOI)000510065900001 ()2-s2.0-85078777950 (Scopus ID)
Note

QC 20200609

Available from: 2020-03-20 Created: 2020-03-20 Last updated: 2022-06-26Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-8318-1251

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