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265 results on '"Kharicha, Abdellah"'

44. Discussion on Modeling Capability for Macrosegregation

Author

Wu Menghuai, Kharicha Abdellah, and Ludwig Andreas

Subjects
macrosegregation, solidification, crystal growth, heat and mass transfer, porosity, diffusion kinetics, Technology, Chemical technology, TP1-1185, Chemicals: Manufacture, use, etc., TP200-248
Abstract

Macrosegregation originates from the solute partitioning at the liquid-solid interface and the relative motion between liquid and solid phases during solidification of metal alloys. A suitable macrosegregation model should incorporate solidification thermodynamics, crystal growth kinetics, multiphase computational fluid dynamics, and even thermal-structural mechanics. No current model includes all those phenomena, hence leading to assumptions having to be made. This paper discusses some modeling assumptions regarding the treatment of (1) diffusion kinetics of crystal growth, (2) crystal dendritic morphology and (3) solidification shrinkage. Theoretical analyses based on test calculations were made. We find that some previous models, which over-simplified some of the aspects mentioned above for the purpose of computational efficiency, can only be applied to study macrosegregation qualitatively. They lead to significant error estimations of macrosegregation. When the quantitative accuracy for macrosegregation is of primary importance, the multiphase-based models with an appropriate treatment of these aspects, despite the sophisticated computational requirements, are recommended.

Published
2017
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46. Impact of Submerged Entry Nozzle (SEN) Immersion Depth on Meniscus Flow in Continuous Casting Mold under Electromagnetic Brake (EMBr)

Author

Vakhrushev, Alexander, Karimi-Sibaki, Ebrahim, Boháček, Jan, Wu, Menghuai, Ludwig, Andreas, Tang, Yong, Hackl, Gernot, Nitzl, Gerald, Watzinger, Josef, Kharicha, Abdellah, Vakhrushev, Alexander, Karimi-Sibaki, Ebrahim, Boháček, Jan, Wu, Menghuai, Ludwig, Andreas, Tang, Yong, Hackl, Gernot, Nitzl, Gerald, Watzinger, Josef, and Kharicha, Abdellah

Abstract

Complex multi-phase phenomena, including turbulent flow, solidification, and magnetohydrodynamics (MHD) forces, occur during the continuous casting (CC) under the applied electromagnetic brake (EMBr). The results of the small-scale experiment of the liquid metal model for continuous casting (mini-LIMMCAST) at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), investigating MHD flow with a deep immersion depth of 100 mm, are supplemented by newly presented numerical studies with the shallow position of the submerged entry nozzle (SEN) at 50 mm below the meniscus. Herein, the focus is on the MHD effects at the meniscus level considering (i) a fully insulating domain boundary, (ii) a perfectly conductive mold, or (iii) the presence of the solid shell. The volume-of-fluid (VOF) approach is utilized to model a Galinstan flow, including free surface behavior. A multiphase solver is developed using conservative MHD formulations in the framework of the open-source computational fluid dynamics (CFD) package OpenFOAM®. The wall-adapting local eddy-viscosity (WALE) subgrid-scale (SGS) model is employed to model the turbulent effects on the free surface flow. We found that, for the deep immersion depth, the meniscus remains calm under the EMBr for the conductive and semi-conductive domain. For the insulated mold disregarding the SEN position, the self-inducing MHD vortices, aligned with the magnetic field, cause strong waving of the meniscus and air bubble entrapment for shallow immersion depth. Secondary MHD structures can form close to the meniscus under specific conditions. The influence of the EMBr and immersion depth on the flow energy characteristics is analyzed using power spectral density (PSD).

Published
2023

47. Transient Simulation of Diffusion-Limited Electrodeposition Using Volume of Fluid (VOF) Method

Author

Karimi-Sibaki, Ebrahim, Vakhrushev, Alexander, Wu, Menghuai, Ludwig, Andreas, Boháček, Jan, Kharicha, Abdellah, Karimi-Sibaki, Ebrahim, Vakhrushev, Alexander, Wu, Menghuai, Ludwig, Andreas, Boháček, Jan, and Kharicha, Abdellah

Abstract

A numerical model utilizing the volume of fluid (VOF) method is proposed to simulate the transient shape changes of the deposit front, considering the diffusion-limited electrodeposition process. Modeling equations are proposed to accurately handle transport phenomena in both electrolyte (fluid) and deposit (solid). Transient evolutions of field structures, including flow, concentration, electric current density, and electric potential, are computed considering electrodeposited copper bumps. Two cases, including single cavity and multiple cavities, are studied. Based on the modeling results, the maximum height of the hump and the thickness of the deposited layer in each consecutive cavity decreases going from upstream to downstream. Conversely, the location of the maximum height of the hump remains unchanged in all cavities. Results are validated against available experiments.

Published
2023

48. Experimental and Numerical Investigations into Heat Transfer Using a Jet Cooler in High-Pressure Die Casting

Author

Boháček, Jan, Mráz, Kryštof, Krutiš, Vladimír, Kaňa, Václav, Vakhrushev, Alexander, Karimi-Sibaki, Ebrahim, Kharicha, Abdellah, Boháček, Jan, Mráz, Kryštof, Krutiš, Vladimír, Kaňa, Václav, Vakhrushev, Alexander, Karimi-Sibaki, Ebrahim, and Kharicha, Abdellah

Abstract

During high-pressure die casting, a significant amount of heat is dissipated via the liquid-cooled channels in the die. The jet cooler, also known as the die insert or bubbler, is one of the most commonly used cooling methods. Nowadays, foundries casting engineered products rely on numerical simulations using commercial software to determine cooling efficiency, which requires precise input data. However, the literature lacks sufficient investigations to describe the spatial distribution of the heat transfer coefficient in the jet cooler. In this study, we propose a solver using the open-source CFD package OpenFOAM and free library for nonlinear optimization NLopt for the inverse heat conduction problem that returns the desired distribution of the heat transfer coefficient. The experimental temperature measurements using multiple thermocouples are considered the input data. The robustness, efficiency, and accuracy of the model are rigorously tested and confirmed. Additionally, temperature measurements of the real jet cooler are presented.

Published
2023

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