Numerical study of the role of mush permeability in the solidifying mushy zone under forced convection

Zhang, Haijie; Wu, Menghuai; Zheng, Yufeng; Ludwig, Andreas; Kharicha, Abdellah

doi:10.1016/j.mtcomm.2019.100842

Cited by 6 publications

(4 citation statements)

References 38 publications

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“…Moreover, in the model used, the permeability of the porous medium in the mushy zone depends on such numerical parameters as DAS taken from the literature. And more detailed studies of the effect of permeability on the interaction of the two velocities considered are needed [46].…”

Section: Flow Into the Mushy Zonementioning

confidence: 99%

Numerical simulation of the EM forced flow during Sn-Pb alloy directional horizontal solidification

Shvydkiy¹,

Smolyanov²,

Baake³

2022

Preprint

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This article presents a study of the influence of electromagnetically (EM) forced convection on segregation formation. As a reference case the solidification of Sn-5 wt pct Pb alloy from the Hebditch and Hunt experiment is taken. Applied forcing of convective flow is determined by the dimensionless electromagnetic forcing parameter F . The study was carried out in the range −3.5 × 10 6 < F < 3.5 × 10 6 . Velocity profiles and flow patterns in the liquid phase are obtained for different applied EM forcing conditions. As a result of parametric analysis, the dependence of the Reynolds number on the electromagnetic forcing parameter was obtained. Electromagnetic forces can significantly affect the flow in the liquid bulk, increasing and slowing down the velocity, as well as changing the circulating flow direction. Solute concentration distribution analysis has shown that EM-forced convection does not affect global solute segregation formation. For the two cases, segregation channels were obtained. However, the analysis of the global segregation index showed that an increase in the Reynolds number provokes a slight decrease in this parameter. The main mechanism of segregation formation is transport of solute rich liquid into the mushy zone. In considered numerical experiment configuration, the penetration into the mushy zone is not large, and even a change in the direction of convection in the liquid bulk does not significantly affect the mushy zone flow. The calculations were made by means of open source code in OpenFOAM and Elmer.

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Section: Flow Into the Mushy Zonementioning

confidence: 99%

Numerical simulation of the EM forced flow during Sn-Pb alloy directional horizontal solidification

Shvydkiy¹,

Smolyanov²,

Baake³

2022

Preprint

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“…The flow pattern in the mushy zone is similar to that in the bulk liquid, although the fluid flow is suppressed by the dendrites to a low magnitude. [5] As demonstrated by the iso-surface in Figure 5(a), the solute-enriched interdendritic liquid is swept to the centre of the sample, leading to the formation of a central macrosegregation channel with some sidearms. The shape of the central segregation is sometimes referred to as ''Christmas tree''.…”

Section: Flow Pattern and Solidificationmentioning

confidence: 99%

“…[4] The resulting microstructural features in the mushy zone can in turn affect the fluid flow by changing the flow intensity and flow pattern. [5] A recent experimental study has demonstrated the importance of the above flow-solidification interaction in the formation of the microstructure, i.e., the flow can adapt the coarsening law. [2,6] Classically, the coarsening law is described by the correlation between the secondary dendrite arm spacing (k 2 ) and the local solidification time (t f ) [7,8] :…”

Section: Introductionmentioning

confidence: 99%

“…In most numerical models k 2 was usually assumed to be a constant value for calculating the mushy permeability, and it was taken from the as-solidified structure. [5,11] This assumption may reduce the credibility of the numerical model, as k 2 is known to change with time due to coarsening/ripening. Recently, a general coarsening equation that accounts for the effects of growth, curvature-driven coarsening, and interface coalescence was proposed by Neumann-Heyme et al [12] The interfacial area density (S v ) was described as a function of the local liquid volume fraction and time.…”

Section: Introductionmentioning

confidence: 99%

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Directional Solidification of AlSi7Fe1 Alloy Under Forced Flow Conditions: Effect of Intermetallic Phase Precipitation and Dendrite Coarsening

Zhang

Rodrigues

et al. 2021

Metall Mater Trans A

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A forced flow was experimentally shown to influence the solidification microstructure of metal alloys by modifying the coarsening/ripening law. In some technical alloys (AlSi7Fe1), this flow effect can also be significantly suppressed due to the formation of intermetallic precipitates (β-Al5FeSi) that can block the flow in the mushy region. The forced flow was induced by a rotating magnetic field (RMF). Herein, a three-phase volume-average-based solidification model is introduced to reproduce the above experiment. The three phases are the melt, the primary solid phase of columnar dendrites, and the second solid phase of intermetallic precipitates. The dynamic precipitation of the intermetallic phase is modelled, and its blocking effect on the flow is considered by a modified permeability. Dendrite coarsening, which influences the permeability, is also considered. The RMF induces a strong azimuthal flow and a relatively weak meridional flow (Ekman effect) at the front of the mushy zone during unidirectional solidification. This forced flow reduces the mushy zone thickness, induces the central segregation channel, affects the distribution of the intermetallic precipitates, and influences dendrite coarsening, which in turn modifies the interdendritic flow. Both interdendritic flow and the microstructure formation are strongly coupled. The modelling results support the explanation of Steinbach and Ratke—the formed intermetallic precipitates (β-Al5FeSi) can block the interdendritic flow, and hence influence the coarsening law. The distribution of β-Al5FeSi is dominantly influenced by the flow-induced macrosegregation. The simulation results of the Si and Fe distribution across the sample section are compared with the experimental results, showing good simulation–experiment agreement. Graphic Abstract During alloy solidifications the flow can influence the mushy zone by inducing macrosegregation, modifying the solidification microstructure, and influencing the formation of intermetallic precipitates. The resulting microstructural features can in turn affect the melt flow by changing the flow intensity and flow pattern. A three-phase volume-average-based solidification model is introduced to study the flow-solidification interaction, and hence to improve the knowledge on the formation mechanism of intermetallics and their effect on solidification. (a) Schematic for the flow pattern and formation of different phases; (b) experiment–simulation comparison of macrosegregation (Fe) across the diameter of as-solidified sample.

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Experimental Evaluation of MHD Modeling of EMS During Continuous Casting

Zhang

et al. 2022

Metall Mater Trans B

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Electromagnetic stirring (EMS) has been recognized as a mature technique in steel industry to control the as-cast structure of steel continuous casting (CC), and computational magnetohydrodynamic (MHD) methods have been applied to study the EMS efficiency. Most MHD methods de-coupled the calculations of electromagnetic and flow fields or simplifications were made for the flow–electromagnetic interactions. However, the experimental validations of the MHD modeling have been rarely reported or very limited. In this study, we present a benchmark, i.e., a series of laboratory experiments, to evaluate the MHD methods, which have been typically applied for steel CC process. Specifically, a rotating magnetic field (RMF) with variable intensity and frequency is considered. First experiment is performed to measure the distribution of magnetic field without any loaded sample (casting); the second experiment is conducted to measure the RMF-induced torque on a cylindrical sample (different metals/alloys in solid state); the third experiment is (based on a special device) to measure the RMF-induced rotational velocity of the liquid metal (Ga75In25), which is enclosed in a cylindrical crucible. The MHD calculation is performed by coupling ANSYS Maxwell and ANSYS Fluent. The Lorentz force, as calculated by analytical equations, ANSYS Fluent addon MHD module, and external electromagnetic solver, is added as the source term in Navier–Stokes equation. By comparing the simulation results with the benchmark experiments, the calculation accuracy with different coupling methods and modification strategies is evaluated. Based on this, a necessary simplification strategy of the MHD method for CC is established, and application of the simplified MHD method to a CC process is demonstrated.

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Numerical study of the role of mush permeability in the solidifying mushy zone under forced convection

Cited by 6 publications

References 38 publications

Numerical simulation of the EM forced flow during Sn-Pb alloy directional horizontal solidification

Numerical simulation of the EM forced flow during Sn-Pb alloy directional horizontal solidification

Directional Solidification of AlSi7Fe1 Alloy Under Forced Flow Conditions: Effect of Intermetallic Phase Precipitation and Dendrite Coarsening

Experimental Evaluation of MHD Modeling of EMS During Continuous Casting

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