NUMERICAL MODELLING OF MAGNETIC SHIELDING BY A CYLINDRICAL FERROFLUID LAYER

A coupled method of finite differences and boundary elements is applied to solve a nonlinear transmission problem of magnetostatics. The problem describes an interaction of a uniform magnetic field with a cylindrical ferrofluid layer. Ferrofluid magnetisations, based on expansions over the Langevin law, are considered to model ferrofluids with a different concentration of ferroparticles. The shielding effectiveness factor of the cylindrical thick-walled ferrofluid layer is calculated depending on intensities of the uniform magnetic field and on thickness of the ferrofluid layer.

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Studies on Magnetic Shielding Effectiveness by Finite Element Method

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.79-82.1233 ◽

2009 ◽

Vol 79-82 ◽

pp. 1233-1236

Author(s):

G.H. Wu ◽

Xiao Li Huang ◽

Mao Qiang Duan ◽

Qiang Zhang ◽

X. Chen

Keyword(s):

Magnetic Field ◽

Finite Element Method ◽

Finite Element ◽

Uniform Magnetic Field ◽

Double Layers ◽

Magnetic Shielding ◽

Shielding Effectiveness ◽

Magnetic Shield ◽

Iron Plate ◽

Circular Shape

Maxwell 2D software is introduced in this paper to calculate the magnetic shielding effectiveness (MSE) properties of iron plate. The three-dimensional magnetic shield is thought isotropic and simplified as two-dimensional model to study its MSE properties by the finite element method. In this method, a uniform magnetic field is generated by two huge magnets and the MSE properties of iron plate, which is in the centre of the uniform magnetic field, is then calculated by the ratio of magnetic field intensity after and before magnetic shielding. All the results indicate that shape of shield materials affects the MSE properties much and the MSE properties of shield with square and circular shape with 3mm in depth are 39.3 and 53.5 dB, respectively. That means the shield shape with fewer bending is favorable to the conductivity of magnetic energy. It also shows that the MSE value decreased linearly with the distance between the magnetic shield and the centre of the magnetic field. That is, the increase of side length of magnetic shield will lead to the decrease of MSE properties of iron plate, which is agreement with the theoretical prediction of Lu H.M. model. Furthermore, the MSE properties of double layers shielding (iron plate with 2mm in depth and 3mm iron plate with 81% porosity) are also studied in this paper. The effect of places of iron plate with 2mm in depth is presented to play important role in double layers shielding and the MSE value increases with the distance between the two magnetic shields. Compared to that of shield with circular shape, the MSE properties are similar to each other when the distance of the two shields is 8mm. In addition, it also indicates that the MSE value is higher when the iron plate with 2mm in depth is inside of the other than that when it is outside.

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Numerical modelling of rotating tangential layers (jets) in shells under strong uniform magnetic field

International Journal for Numerical Methods in Fluids ◽

10.1002/fld.2036 ◽

2009 ◽

pp. n/a-n/a

Author(s):

D. K. Fidaros ◽

L. Bühler ◽

A. P. Grecos ◽

N. S. Vlachos

Keyword(s):

Magnetic Field ◽

Numerical Modelling ◽

Uniform Magnetic Field

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ASYMPTOTIC SOLUTION FOR THE FLOW DUE TO AN INFINITE ROTATING DISK IN THE CASE OF LARGE MAGNETIC FIELD

Transactions of the Canadian Society for Mechanical Engineering ◽

10.1139/tcsme-2000-0038 ◽

2000 ◽

Vol 24 (3-4) ◽

pp. 515-523 ◽

Cited By ~ 1

Author(s):

Tarek M.A. El-Mistakawy ◽

Hazem A. Attia ◽

Adel A. Megahed

Keyword(s):

Magnetic Field ◽

Asymptotic Expansion ◽

Asymptotic Solution ◽

Finite Differences ◽

Uniform Magnetic Field ◽

Magnetic Interaction ◽

Rotating Disk ◽

Exact Numerical Solution ◽

Infinite Extent ◽

Expansion Coefficients

The flow due to a rotating disk of infinite extent is studied in the presence of an axial uniform magnetic field in the case of large magnetic interaction number ß. The solution is given in the form of an asymptotic expansion in powers of ß-2 whose coefficients are obtained in closed form in terms of a properly scaled von Karman’s similarity coordinate that is strained to remove a secular behavior. The process of finding the expansion coefficients is found to be systematic, which makes it possible to produce as many terms of the expansion as may be needed. A comparison between the asymptotic solution and the exact numerical solution which uses finite-differences and linearization is done to check the results of the asymptotic expansion and determine its range of validity.

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Validation of a measurement method for magnetic shielding effectiveness of a wire mesh enclosure with comparison to an analytical model

Advances in Radio Science ◽

10.5194/ars-11-189-2013 ◽

2013 ◽

Vol 11 ◽

pp. 189-195 ◽

Cited By ~ 2

Author(s):

M. Kühn ◽

W. John ◽

R. Weigel

Keyword(s):

Magnetic Field ◽

Analytical Model ◽

Helmholtz Coil ◽

Wire Mesh ◽

Magnetic Shielding ◽

Shielding Effectiveness ◽

Electro Magnetic Field ◽

Signal Amplifier ◽

Electro Magnetic ◽

The Magnetic Field

Abstract. This paper deals with the validation of a measurement method for determining the magnetic shielding effectiveness of a wire mesh enclosure in the frequency range from 10 kHz to 150 kHz. The comparison with an analytical model (parallel-plate-shield, see Kaden, 1959) for magnetic shielding effectiveness of wire mesh is also part of this contribution. To measure the shielding effectiveness of an enclosure in general, two steps are necessary: 1. Reference measurement of the incident electro-magnetic field. 2. Measurement of the incident electro-magnetic field in the enclosure by same conditions. This method presented in the contribution uses a Helmholtz coil as magnetic field source, controlled by a signal generator and an amplifier in voltage mode. At first, a field meter was used to measure the frequency dependent magnetic field in the center of the Helmholtz coil. The magnetic field strength was also analytically calculated and compared to the measurement results. The next step was to measure the induction voltage caused by the magnetic field with a magnetic field probe, which was later used for the measurements of the shielding effectiveness either. A signal amplifier was needed to raise the signal-to-noise-ratio (SNR). The gain of the signal amplifier was also determined and measured. Two positions of the enclosure in the Helmholtz coil were considered, horizontal and vertical. The vertical position of the enclosure approaches the analytical model of Kaden (1959) closely and the results show a good match with the analytical model.

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XXVI.—Magnetic Shielding in Hollow Iron Cylinders and Superposed Inductions in Iron

Transactions of the Royal Society of Edinburgh ◽

10.1017/s0080456800034748 ◽

1905 ◽

Vol 40 (3) ◽

pp. 631-681 ◽

Cited By ~ 1

Author(s):

James Russell

Keyword(s):

Magnetic Field ◽

Uniform Magnetic Field ◽

Shielding Effect ◽

Magnetic Shielding ◽

Du Bois ◽

The Subject ◽

Image Position

§ 1. The shielding effect which exists within hollow iron spheres and cylinders, when placed in a uniform magnetic field, has been previously investigated. Poisson, Stefan, Maxwell, and among others, and more recently, Professors Rücker and Du Bois, have contributed to the subject. Ifand the ratio of n to R be the order 1 to 100, it appears that the following expressions may be taken as sufficiently correct:

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