scholarly journals Analysis of the Effect of a Vertical Magnetic Field on Melt Convection and Oxygen Transport During Directional Solidification of Multi-Crystalline Silicon by Numerical Simulation

Crystals ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 8
Author(s):  
Botao Song ◽  
Yufeng Luo ◽  
Senlin Rao ◽  
Fayun Zhang ◽  
Yun Hu
Keyword(s):  
Magnetic Field ◽  
Numerical Simulation ◽  
Directional Solidification ◽  
Oxygen Concentration ◽  
Crystalline Silicon ◽  
Vertical Magnetic Field ◽  
Silicon Melt ◽  
Average Oxygen Concentration ◽  
Melt Convection ◽  
The Magnetic Field

Melt convection during the directional solidification process of multi-crystalline silicon plays a critical role in the transport of impurities. The utilization of a static magnetic field is an effective way to control the melt convection pattern. Studying the effect of the Lorentz force induced by the vertical magnetic field (VMF) on the melt convection of silicon in detail is beneficial to optimize the magnetic field parameters in the production process. Based on the numerical simulation method of multi-physics coupling, this paper explores the effects of different VMF intensities on the convection of silicon melt and the transport of oxygen in the melt during the directional solidification of polycrystalline silicon. The results show that in the first 125 minutes of the crystallization stage, the melt convection velocity is affected significantly by the magnetic field intensities. When different convection circulations are present in the silicon melt, the upper circulation easily transports oxygen to the furnace atmosphere, and the subjacent circulation easily lead to the retention and accumulation of oxygen. Enhancing the VMF intensity to a certain extent can reduce the size of the oxygen retention region in the silicon melt, and the time of the first disappearance of the subjacent circulation near the sidewall of the crucible is shortened. Then the average oxygen concentration in the silicon melt can be reduced. However, a larger vertical magnetic field intensity can result in greater average oxygen concentration in the oxygen retention region.

HEXAGON-STRIPE TRANSITION AT THE MAGNETIC FIELD INDUCED PHASE TRANSFORMATIONS OF THE MAGNETORHEOLOGICAL SUSPENSIONS

2002 ◽  
Vol 16 (17n18) ◽  
pp. 2345-2351 ◽  
Author(s):  
A. CEBERS
Keyword(s):  
Magnetic Field ◽  
Numerical Simulation ◽  
Physical Parameters ◽  
Phase Boundaries ◽  
Modulated Phases ◽  
Magnetorheological Suspensions ◽  
Perturbed State ◽  
Magnetorheological Suspension ◽  
The Magnetic Field ◽  
Hele Shaw Cell

The phase diagram of the magnetorheological suspension allowing for the modulated phases in the Hele-Shaw cell under the action of the normal field is calculated. The phase boundaries between the stripe, the hexagonal and the unmodulated phases in dependence on the layer thickness and the magnetic field strength are found. The existence of the transitions between the stripe and the hexagonal phases at the corresponding variation of the physical parameters is illustrated by the numerical simulation of the concentration dynamics in the Hele-Shaw cell. It is remarked that those transitions in the case of the magnetorheological suspensions can be caused by the compression or the expansion of the layer. Among the features noticed at the numerical simulation of the concentration dynamics in the Hele-Shaw cell are: the stripe patterns formed from the preexisting hexagonal structures are more ordered than arising from the initial randomly perturbed state; at the slightly perturbed boundary between the concentrated and diluted phases the hexagonal and the inverted hexagonal phases are formed and others.

Effect of magnetic field on parametrically driven surface waves

2006 ◽  
Vol 463 (2079) ◽  
pp. 711-722 ◽  
Author(s):  
Supriyo Paul ◽  
Krishna Kumar
Keyword(s):  
Magnetic Field ◽  
Surface Waves ◽  
Liquid Metals ◽  
Tricritical Point ◽  
Thin Layers ◽  
Vertical Magnetic Field ◽  
Harmonic Solution ◽  
Chandrasekhar Number ◽  
The Magnetic Field ◽  
Primary Instability

Stability analysis of parametrically driven surface waves in liquid metals in the presence of a uniform vertical magnetic field is presented. Floquet analysis gives various subharmonic and harmonic instability zones. The magnetic field stabilizes the onset of parametrically excited surface waves. The minima of all the instability zones are raised by a different amount as the Chandrasekhar number is raised. The increase in the magnetic field leads to a series of bicritical points at a primary instability in thin layers of a liquid metal. The bicritical points involve one subharmonic and another harmonic solution of different wavenumbers. A tricritical point may also be triggered as a primary instability by tuning the magnetic field.

Numerical Simulation of High-Aspect-Ratio Micro-Hole Electroforming with External Magnetic Field

2010 ◽  
Vol 42 ◽  
pp. 13-16
Author(s):  
Wei Li ◽  
Ping Mei Ming ◽  
Wu Ji Jiang ◽  
Yin Ding Lv
Keyword(s):  
Magnetic Field ◽  
Numerical Simulation ◽  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Flow State ◽  
Cathode Electrode ◽  
Micro Hole ◽  
Fluent Software ◽  
The Magnetic Field ◽  
Enhance Mass

In this paper, the influences of applied magnetic field on flow state during electroforming of the high-aspect-ratio (HAR) blind micro-hole were numerically analyzed using the Fluent software. The results showed that, when microelectroforming of nickel without external agitation, three vortexes could form due to the magnetohydrodynamic (MHD) effect within the HAR micro-hole with magnetic field in parallel to cathode-electrode surface, and the flow rate in the micro-hole increased with the increase of the magnetic field and current density. The MHD effect helped to enhance mass transfer during the microelectroforming of HAR microstructures.

scholarly journals Properties of the inner penumbral boundary and temporal evolution of a decaying sunspot

2018 ◽  
Vol 620 ◽  
pp. A191 ◽  
Author(s):  
M. Benko ◽  
S. J. González Manrique ◽  
H. Balthasar ◽  
P. Gömöry ◽  
C. Kuckein ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Temporal Evolution ◽  
Vertical Component ◽  
Field Vector ◽  
Linear Increase ◽  
Vertical Magnetic Field ◽  
Magnetic Diffusion ◽  
The Magnetic Field ◽  
Linear Decay

Context. It has been empirically determined that the umbra-penumbra boundaries of stable sunspots are characterized by a constant value of the vertical magnetic field. Aims. We analyzed the evolution of the photospheric magnetic field properties of a decaying sunspot belonging to NOAA 11277 between August 28–September 3, 2011. The observations were acquired with the spectropolarimeter on-board of the Hinode satellite. We aim to prove the validity of the constant vertical magnetic-field boundary between the umbra and penumbra in decaying sunspots. Methods. A spectral-line inversion technique was used to infer the magnetic field vector from the full-Stokes profiles. In total, eight maps were inverted and the variation of the magnetic properties in time were quantified using linear or quadratic fits. Results. We find a linear decay of the umbral vertical magnetic field, magnetic flux, and area. The penumbra showed a linear increase of the vertical magnetic field and a sharp decay of the magnetic flux. In addition, the penumbral area quadratically decayed. The vertical component of the magnetic field is weaker on the umbra-penumbra boundary of the studied decaying sunspot compared to stable sunspots. Its value seem to be steadily decreasing during the decay phase. Moreover, at any time of the sunspot decay shown, the inner penumbra boundary does not match with a constant value of the vertical magnetic field, contrary to what is seen in stable sunspots. Conclusions. During the decaying phase of the studied sunspot, the umbra does not have a sufficiently strong vertical component of the magnetic field and is thus unstable and prone to be disintegrated by convection or magnetic diffusion. No constant value of the vertical magnetic field is found for the inner penumbral boundary.

Instability and transition of a vertical ascension or fall of a free sphere affected by a vertical magnetic field

2018 ◽  
Vol 859 ◽  
pp. 33-48 ◽  
Author(s):  
Jun-Hua Pan ◽  
Nian-Mei Zhang ◽  
Ming-Jiu Ni
Keyword(s):  
Magnetic Field ◽  
Interaction Parameter ◽  
Scaling Law ◽  
Density Ratio ◽  
Vertical Magnetic Field ◽  
Streamwise Vorticity ◽  
Close Relationship ◽  
Wake Patterns ◽  
The Magnetic Field ◽  
Solid System

When the Galileo number is below the first bifurcation, the instability and transition of a vertical ascension or the fall of a free sphere affected by a vertical magnetic field are investigated numerically. A compact model is used to explain that the magnetic field can destabilize the fluid–solid system. When the interaction parameter exceeds a critical value, the sphere trajectory is transitioned from a steady vertical trajectory to a steady oblique one. Furthermore, the trajectory will remain vertical at a sufficiently large magnetic field because of a double effect of the magnetic field on the fluid–solid system. Under the influence of an external vertical magnetic field, four wake patterns at the rear of the sphere are found and the physical behaviour of the free sphere is independent of the density ratio. The wake or trajectory of the free sphere is only determined by the Galileo number $G$ and the interaction parameter $N$. A close relationship between the streamwise vorticity and the sphere motion is found. An interesting ‘agglomeration phenomenon’ is also found, which shows that the vertical velocities are agglomerated into a point for a certain magnetic field regardless of the Galileo number and satisfy a scaling law $V_{z}\sim N^{-1/4}$, when $N>1$. The principal results of the present work are summarized in a map of regimes in the $\{G,N\}$ plane.

scholarly journals Numerical simulation of induction heating thick-walled tubes

2018 ◽  
Vol 168 ◽  
pp. 02004
Author(s):  
Richard Lenhard ◽  
Milan Malcho ◽  
Katarína Kaduchová
Keyword(s):  
Magnetic Field ◽  
Numerical Simulation ◽  
Field Distribution ◽  
Induction Heating ◽  
Electromagnetic Induction ◽  
Magnetic Field Distribution ◽  
The Magnetic Field ◽  
Heated Material ◽  
Ansys Workbench

In the paper is shown the connection of two toolboxes in an Ansys Workbench solution for induction heating. In Ansys Workbench, Maxwell electromagnetism programs and Fluent have been linked. In Maxwell, a simulation of electromagnetic induction was performed, where data on the magnetic field distribution in the heated material was obtained and then transformed into the Fluent program in which the induction heating simulation was performed.

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