Numerical Simulation of Electromagnetic Phenomena and Solidification under a Pulsed Magnetic Field

2019 ◽  
Vol 944 ◽  
pp. 52-58
Author(s):  
Qi Peng Chen ◽  
Hidetaka Oguma ◽  
Hou Fa Shen
Keyword(s):  
Magnetic Field ◽  
Temperature Field ◽  
Lorentz Force ◽  
Periodic Oscillation ◽  
Side Surface ◽  
Pulsed Magnetic Field ◽  
Magnetic Flux Density ◽  
Meridian Plane ◽  
Cu Alloy ◽  
Transient Electromagnetic

The transient electromagnetic phenomena and solidification of Al-Cu alloy under a typical pulsed magnetic field (PMF) are numerically studied by a two-dimensional (2D) axisymmetric model. The results show that the magnetic flux density, eddy current density, Lorentz force and Joule heat all inherit the instantaneous and intermittent feature of the PMF, and their amplitudes and phases decrease with the increasing distance to the side surface of the ingot. The Lorentz force appears alternatively as pressure force and pull force mainly in the radial direction. Forced convection is induced in the liquid metal, and the flow field is composed of a clockwise vortex and a counter-clockwise vortex in the meridian plane of the ingot. The melt velocity is accompanied with a dramatic periodic oscillation. The temperature field in the ingot with the PMF tends uniform due to the mixing effect of the melt flow. However, the convection is damped soon after the solidification starts due to the increasing penetration resistance, and the temperature field gradually approximates that in the case without the PMF.

scholarly journals Ablation in Externally Applied Electric and Magnetic Fields

Nanomaterials ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 182
Author(s):  
Jovan Maksimovic ◽  
Soon-Hock Ng ◽  
Tomas Katkus ◽  
Nguyen Hoai An Le ◽  
James W.M. Chon ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Laser Ablation ◽  
Lorentz Force ◽  
Negative Electrode ◽  
Magnetic Flux Density ◽  
Ripple Formation ◽  
Electric And Magnetic Fields ◽  
Potential Applications ◽  
Application Potential ◽  
X Ray Absorption

To harness light-matter interactions at the nano-/micro-scale, better tools for control must be developed. Here, it is shown that by applying an external electric and/or magnetic field, ablation of Si and glass under ultra-short (sub-1 ps) laser pulse irradiation can be controlled via the Lorentz force F = e E + e [ v × B ] , where v is velocity of charge e, E is the applied electrical bias and B is the magnetic flux density. The external electric E-field was applied during laser ablation using suspended micro-electrodes above a glass substrate with an air gap for the incident laser beam. The counter-facing Al-electrodes on Si surface were used to study debris formation patterns on Si. Debris was deposited preferentially towards the negative electrode in the case of glass and Si ablation. Also, an external magnetic field was applied during laser ablation of Si in different geometries and is shown to affect ripple formation. Chemical analysis of ablated areas with and without a magnetic field showed strong chemical differences, revealed by synchrotron near-edge X-ray absorption fine structure (NEXAFS) measurements. Harnessing the vectorial nature of the Lorentz force widens application potential of surface modifications and debris formation in external E-/B-fields, with potential applications in mass and charge spectroscopes.

PDMS Membrane Microactuator for Focal Tunable Microlens

2006 ◽  
Author(s):  
Seok Woo Lee ◽  
Seung S. Lee
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Flux Density ◽  
Lorentz Force ◽  
Spin Coating ◽  
Large Displacement ◽  
Pdms Membrane ◽  
Magnetic Flux Density ◽  
Optical Performance ◽  
Electrical Components

In this paper, PDMS membrane for a large displacement is fabricated by new fabrication process which can be integrated with electrical components on substrates fabricated by conventional microfabrication processes and the performance of the membrane using electromagnetism was evaluated. Rectangular PDMS membranes are designed as 2mm and 3mm in width, respectively and are actuated by Lorentz force induced by current paths spread on the membrane. The PDMS membrane is fabricated by reducing a viscosity of uncured PDMS with dilution and spin coating on the substrate on which electric components generating Lorentz force. Finally, PDMS membrane including electric components is opened by a bulk micromachining. The device is tested in magnetic field induced by Nd-Fe-B magnet whose magnetic flux density is 90G. When applied currents are 20, 25, and 30mA, the maximum deflections of membranes are 1.21, 3.07, and 20.2μm for 1.5mm width membrane and 3.34, 31.0, and 50.9μm for width 3mm membrane, respectively. The large displacement PDMS membrane actuator has potentially various applications such as fluidics, optics, acoustics, and electronics. Currently, we are planning to measure the optical performance of the actuator as a focal tunable liquid lens.

Galvanomagnetic and thermomagnetic phenomena

2004 ◽  
Author(s):  
Robert E. Newnham
Keyword(s):  
Magnetic Field ◽  
Heat Flow ◽  
Magnetic Fields ◽  
Hall Effect ◽  
Electric Current ◽  
Lorentz Force ◽  
Electrical Resistance ◽  
Magnetic Flux Density ◽  
Wide Range ◽  
The Magnetic Field

The Lorentz force that a magnetic field exerts on a moving charge carrier is perpendicular to the direction of motion and to the magnetic field. Since both electric and thermal currents are carried by mobile electrons and ions, a wide range of galvanomagnetic and thermomagnetic effects result. The effects that occur in an isotropic polycrystalline metal are illustrated in Fig. 20.1. As to be expected, many more cross-coupled effects occur in less symmetric solids. The galvanomagnetic experiments involve electric field, electric current, and magnetic field as variables. The Hall Effect, transverse magnetoresistance, and longitudinal magnetoresistance all describe the effects of magnetic fields on electrical resistance. Analogous experiments on thermal conductivity are referred to as thermomagnetic effects. In this case the variables are heat flow, temperature gradient, and magnetic field. The Righi–Leduc Effect is the thermal Hall Effect in which magnetic fields deflect heat flow rather than electric current. The transverse thermal magnetoresistance (the Maggi–Righi–Leduc Effect) and the longitudinal thermal magnetoresistance are analogous to the two galvanomagnetic magnetoresistance effects. Additional interaction phenomena related to the thermoelectric and piezoresistance effects will be discussed in the next two chapters. In tensor form Ohm’s Law is . . .Ei = ρijJj , . . . where Ei is electrical field, Jj electric current density, and ρij the electrical resistivity in Ωm. In describing the effect of magnetic field on electrical resistance, we expand the resistivity in a power series in magnetic flux density B. B is used rather than the magnetic field H because the Lorentz force acting on the charge carriers depends on B not H.

Investigation of Microcoils for High Magnetic Field Generation

1970 ◽  
Vol 109 (3) ◽  
pp. 63-66 ◽  
Author(s):  
A. Grainys ◽  
J. Novickij
Keyword(s):  
Magnetic Field ◽  
High Voltage ◽  
Capacitor Bank ◽  
Magnetic Flux Density ◽  
Magnetic Field Generation ◽  
High Voltage Power Supply ◽  
Field Generation ◽  
Transient Electromagnetic ◽  
In Series ◽  
Thermodynamic Processes

Microcoils design for high pulsed magnetic field generation is described. A possibility to generate micro and sub-microsecond magnetic field pulses in 1 - 10 T range is analyzed. Pulsed facilities consisting of high voltage power supply, low self-inductance capacitor bank and fast high voltage solid state switches connected in parallel and in series are able to generate high power 1 kA, 0,51,0 )µs pulses. Three different prototypes of single, dual and multiturn microcoils are investigated. Analytical and finite element methods are used for modelling of transient electromagnetic and thermodynamic processes. Computer simulation results of current density, thermal overloads and calculations of axial magnetic flux density are presented and recommendations for further experiments are offered. Ill. 7, bibl. 13 (in English; abstracts in English and Lithuanian).http://dx.doi.org/10.5755/j01.eee.109.3.172

scholarly journals STUDY OF ACOUSTIC SOURCE EXCITED BY PULSED MAGNETIC FIELD

2021 ◽  
pp. 2140008
Author(s):  
YANJU YANG ◽  
CHUNLEI CHENG ◽  
WENYAO YANG ◽  
JIE LI ◽  
ZHENGFU CHENG ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Numerical Simulation ◽  
Analytical Solution ◽  
Magnetic Flux ◽  
Flux Density ◽  
Magnetic Induction ◽  
Pulsed Magnetic Field ◽  
Magnetic Flux Density ◽  
Acoustic Source ◽  
Thermoacoustic Imaging

In magnetoacoustic tomography with magnetic induction and magnetically mediated thermoacoustic imaging, tissues are exposed to an alternating field, generating magnetoacoustic and thermoacoustic effects in the tissues. This study aimed to investigate the relationship between magnetoacoustic and thermoacoustic effects in a low-conductivity object put in a Gauss-pulsed alternating magnetic field. First, the derivations of the magnetic flux density and electric field strength induced by a Gauss-pulsed current flowing through the coil based on the theory of electromagnetic field were examined. Second, the analytical solution of the magnetic field was studied by simulation. To validate the accuracy of the analytical solution, the analytical solution and the numerical simulation of the magnetic flux density were compared. It shows that the analytical solution coincides with the numerical simulation well. Then, based on the theoretical analysis of the acoustic source generation, numerical studies were conducted to simulate pressures excited by magnetoacoustic and thermoacoustic effects in low-conductivity objects similar to tissues in the Gauss-pulsed magnetic field. The thermoacoustic effect played a leading role in low-conductivity objects placed in the Gauss-pulsed magnetic field, and the magnetoacoustic effect could be ignored. This study provided the theoretical basis for further research on magnetoacoustic tomography with magnetic induction and magnetically mediated thermoacoustic imaging for pathological tissues.

Analysis On the Inception of the Magnetohydrodynamic Flow Instability in the Annular Linear Induction Pump Channel

2021 ◽  
Author(s):  
Ruijie Zhao ◽  
Xiaohui Dou ◽  
Qiang Pan ◽  
ZHANG Desheng ◽  
Bart van Esch
Keyword(s):  
Magnetic Field ◽  
Pressure Gradient ◽  
Lorentz Force ◽  
Flow Rate ◽  
Flow Instability ◽  
Fluid Velocity ◽  
Magnetic Reynolds Number ◽  
Wave Number ◽  
Magnetic Flux Density ◽  
Linear Induction

Abstract Flow instability is the intricate phenomenon in the Annular Linear Induction Pump when the pump runs at off-design working condition. A 3D numerical model is built to simulate the flow in the pump channel. The pump heads at different flow rates are accurately predicted by comparing with experiment. The simulation results show the fluid velocity is circumferentially non-uniform in the pump channel even at the nominal flow rate. The flow in the middle sector continuously decelerates to nearly zero with the reducing flow rate. Reversed flow occurs in the azimuthal plane, followed by vortex flow. The reason for the heterogeneous velocity field is attributed to the mismatch between non-uniform Lorentz force and relatively even pressure gradient. It is seen that the flow in the region of small Lorentz force has to sacrifice its velocity to match with the pressure gradient. An analytic expression of the axial Lorentz force is then developed and it is clearly demonstrated the Lorentz force could be influenced by the profiles of velocity and radial magnetic flux density. The coupling between velocity and magnetic field is studied by analyzing the magnitudes of different terms in the dimensionless magnetic induction equation. It is found the dissipation term is determined not only by the magnetic Reynolds number but the square of wave number of the disturbance in each direction. The smaller disturbing wave number weakens the dissipating effect, resulting in the larger non-uniform magnetic field and axial Lorentz force.

Solidification Structure of 6063 Alloy under Pulsed Magnetic Field

2015 ◽  
Vol 817 ◽  
pp. 355-359
Author(s):  
Shi Chao Liu ◽  
Hang Chen ◽  
Jun Jia Zhang ◽  
Peng Fei Wang ◽  
Jin Chuan Jie ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Grain Size ◽  
Temperature Field ◽  
Pulse Frequency ◽  
Dendrite Growth ◽  
Pulsed Magnetic Field ◽  
Solidification Structure ◽  
Cold Wall ◽  
Average Grain Size ◽  
Equiaxed Grains

The influences of pulsed magnetic field (PMF) on solidification structure of 6063 alloy were studied in this article. The results show that solidification structure of 6063 alloy can be refined with the application of PMF. The dendrite growth restrained and the macrostructure changed from large dendrite grains to fine equiaxed grains. The grain size decreased when the voltage increased from 0V to 600V. However, when the pulse frequency increased from 5Hz to 15Hz, the average grain size decreased continuously until reached a limit, and then the grains coarsened with further increase of the pulse frequency. The vibration caused by PMF not only made the temperature field of the melt uniform ,but also brook off the initial solidified grains formed on the cold wall of the mold, and spurs the grains to move to the center of melt which can be acted as nuclei.

Effects of Low-Voltage Pulsed Magnetic Field and Pouring Temperature on Solidified Structure of Al-4.5%Cu Alloy

2011 ◽  
Vol 399-401 ◽  
pp. 2139-2143
Author(s):  
Quan Zhou ◽  
Le Ping Chen ◽  
Jian Yin
Keyword(s):  
Magnetic Field ◽  
Grain Size ◽  
Low Voltage ◽  
Structure Refinement ◽  
Primary Phase ◽  
Pulse Voltage ◽  
Pulsed Magnetic Field ◽  
Pouring Temperature ◽  
Cu Alloy ◽  
Spherical Crystals

The solidified structure refinement of Al-4.5%Cu under the action of low-voltage pulsed magnetic field (LVPMF) was investigated in the paper. The influences of different pulse voltage and pouring temperature on solidified structure of Al-4.5%Cu alloy were studied. The results show that solidified structure of Al-4.5%Cu alloy can be refined greatly by LVPMF processing. The dendrite growth is restrained and the microstructure is changed from larger dendrite grains to smaller nondendritic grains, and with certain parameters, the equiaxed, non-dendritic grains are gained in the alloy. With the increase of pulse voltage, grain size of the alloy decreases, and the primary phase degrades from developed dendrites into rose-like or spherical crystals. The decrease of pouring temperature enhances the refinement effect of LVPMF processing. With 150 V pulse magnetic field treatment, grain size of the alloy decreases, primary phase degrades and refines gradually with the decrease of pouring temperature.

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