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Article
Publication date: 11 January 2011

Sintu Singha and K.P. Sinhamahapatra

The purpose of this paper is to simulate the flow of a conducting fluid past a circular cylinder placed centrally in a channel subjected to an imposed transverse magnetic

Abstract

Purpose

The purpose of this paper is to simulate the flow of a conducting fluid past a circular cylinder placed centrally in a channel subjected to an imposed transverse magnetic field to study the effect of a magnetic field on vortex shedding at different Reynolds numbers varying from 50 to 250.

Design/methodology/approach

The two‐dimensional incompressible laminar viscous flow equations are solved using a second‐order implicit unstructured collocated grid finite volume method.

Findings

An imposed transverse magnetic field markedly reduces the unsteady lift amplitude indicating a reduction in the strength of the shed vortices. It is observed that the periodic vortex shedding at the higher Reynolds numbers can be completely suppressed if a sufficiently strong magnetic field is imposed. The required magnetic field strength to suppress shedding increases with Reynolds number. The simulation shows that the separated zone behind the cylinder in a steady flow is reduced as the magnetic field strength is increased.

Originality/value

In this paper, due attention is given to resolve and study the unsteady cylinder wake and its interaction with the shear‐layer on the channel wall in the presence of a magnetic field. A critical value of the Hartmann number for complete suppression of the shedding at a given Reynolds number is found.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 21 no. 1
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 10 April 2009

Cong‐qian Cheng, Jie Zhao, Yang Xu, Fu‐Min Xu and Ming‐liang Huang

The aim of this paper is to investigate the growth behaviours of intermetallic compound (IMC) layers in solid‐liquid interfacial reactions of Sn1.5Cu/Cu in various…

Abstract

Purpose

The aim of this paper is to investigate the growth behaviours of intermetallic compound (IMC) layers in solid‐liquid interfacial reactions of Sn1.5Cu/Cu in various intensities of high‐magnetic field.

Design/methodology/approach

Sn1.5Cu solder was prepared and melted in a vacuum furnace at 873 K and cast into solder bars. Samples were mounted using resin and etched after being carefully polished. Then the IMC layers were observed by using scanning electron microscopy.

Findings

The results show that the growth of IMC layers has been accelerated by high‐magnetic field through the comparison of growth kinetics of IMC layers among 0‐2.5 T magnetic filed. IMC grains in high‐magnetic field are much bigger than that in 0 T. By the analyzing of X‐ray diffractometer patterns of IMC layers, it can be found that the orientations of IMC have been changed by magnetic field.

Originality/value

This paper investigates the growth behaviour of IMC layers during the solid‐liquid interfacial reactions of Sn1.5Cu/Cu in a high magnetic field.

Details

Soldering & Surface Mount Technology, vol. 21 no. 2
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 21 August 2018

Jacek Horiszny

The paper presents the analysis of magnetic field that surrounds the power transformer after it has been switched off. The purpose of this paper is to determine the…

Abstract

Purpose

The paper presents the analysis of magnetic field that surrounds the power transformer after it has been switched off. The purpose of this paper is to determine the possibility of defining the residual fluxes in the legs of the transformer based on the measurement of this field. It was also intended to determine the type and the location of magnetic sensors.

Design/methodology/approach

Numerical analysis of the magnetic field was performed. A three-dimensional model of the transformer’s magnetic core was created in the Flux 3D simulation program. The analysis was concerned with an oil-filled transformer and a dry transformer. The magnetic field of Earth was taken into account.

Findings

The research has shown that magnetic induction of the leakage field produced by residual magnetization of the core is comparable to the magnetic induction of the Earth’s field. It was also found that the measurement of the magnetic induction should be performed as close as possible to the core. The interior of the tank turned out to be a convenient space for the placement of the sensors.

Research limitations/implications

The influence of external ferromagnetic objects, and devices generating magnetic field, on the measurement was not considered. It should be taken into account in the future work.

Originality/value

On the basis of the analysis, it was proposed to measure the magnetic induction vector of the leakage field at three points. The sensors should be placed in front of the columns at a position that is half of their height. The measurement can be performed with satisfactory accuracy by sensors located on the surface of the windings.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 37 no. 5
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 16 March 2010

Xiaoya He and Yi Lin

The purpose of this paper is to establish the relevant quantitative methods for the investigation of the eddy and meridian fields of the general systemic yoyo model.

Abstract

Purpose

The purpose of this paper is to establish the relevant quantitative methods for the investigation of the eddy and meridian fields of the general systemic yoyo model.

Design/methodology/approach

On the basis of established systemic yoyo models for electrons and positrons, flows of negative yoyo charges are naturally identified with electric currents so that use of the well‐developed quantitative methods can be made in electromagnetic theory to investigate the relationship between eddy and meridian fields of the general systemic yoyo model.

Findings

A general method is established on how to compute the intensity of the magnetic yoyo fields accompanying a moving yoyo charge or a canal of yoyo flow. A quantitative representation for magnetic yoyo fields is provided. And, the well‐known Ampere's law of electricity is generalized to the case of general yoyo flows.

Originality/value

By establishing an adequate quantitative method for the general systemic yoyo model, it should be possible to know more about the yoyo model and gain additional potential to successfully employ this model in various areas of learning, as proposed by Lin.

Details

Kybernetes, vol. 39 no. 2
Type: Research Article
ISSN: 0368-492X

Keywords

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Article
Publication date: 1 February 1982

I. MAYERGOYZ

New iteration methods for the calculation of steady magnetic fields in saturable media are presented. These methods converge for any choice of initial approximation, that…

Abstract

New iteration methods for the calculation of steady magnetic fields in saturable media are presented. These methods converge for any choice of initial approximation, that is they possess global convergence. The convergence conditions and the estimates of convergence rate of these methods are expressed in terms of the physical properties of ferromagnetic media. Each of the proposed methods is deliberately adapted to specific but typical saturation conditions. All these methods together cover the broad area of diverse saturation conditions encountered in practice. The construction and justification of these iteration methods are based on the physical concept of secondary sources and on some mathematical ideas and results arising in the overlapping area of mathematical physics and functional analysis.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 1 no. 2
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 6 November 2017

Xiaojun Zhao, Fanhui Meng, Zhiguang Cheng, Lanrong Liu, Junjie Zhang and Chao Fan

This paper aims to investigate an efficient approach to model the electromagnetic behaviors and predict stray-field loss inside the magnetic steel plate under 3D harmonic…

Abstract

Purpose

This paper aims to investigate an efficient approach to model the electromagnetic behaviors and predict stray-field loss inside the magnetic steel plate under 3D harmonic magnetization conditions so as to effectively prevent the structural components from local overheating and insulation damage in electromagnetic devices.

Design/methodology/approach

An experimental setup is applied to measure all the magnetic properties of magnetic steel plate under harmonic excitations with different frequencies and phase angles. The measurement and numerical simulation are carried out based on the updated TEAM Problem 21 Model B+ (P210-B+), under the 3D harmonic magnetization conditions. An improved method to evaluate the stray-field loss is proposed, and harmonic flux distribution in the structural components is analyzed.

Findings

The influence of the harmonic order and phase angle on the stray-field loss in magnetic steel components are noteworthy. Based on the engineering-oriented benchmark models, the variations of stray-field losses and magnetic field distribution inside the magnetic components under harmonic magnetization conditions are presented and analyzed in detail.

Research limitations/implications

The capacity of the multi-function harmonic source, used in this work, was not large enough, which limits the magnetization level. Up to now, further improvements to increase the harmonic source capacity and investigations of the electromagnetic behaviors of magnetic steel components under multi-harmonic and DC-AC hybrid excitations are in progress.

Originality/value

To accurately predict the stray-field loss in magnetic steel plate, the improved method based on the combination of magnetic measurement and numerical simulation is proposed. The effects of the frequency and phase angle on the stray-field loss are analyzed.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 36 no. 6
Type: Research Article
ISSN: 0332-1649

Keywords

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Article
Publication date: 16 March 2010

Xiaoya He and Yi Lin

The purpose of this paper is to investigate yoyo potential difference and induction of electric yoyo flows by using the general systemic yoyo model and available…

Abstract

Purpose

The purpose of this paper is to investigate yoyo potential difference and induction of electric yoyo flows by using the general systemic yoyo model and available quantitative tools.

Design/methodology/approach

Empirical laws and well‐known laboratory experiments of physics are revisited in light of the spinning yoyo method and thinking logic. When appropriate, relevant quantitative methods are established.

Findings

By generalizing the concept of electromotive force, the paper introduces that of meridian motive forces (MMF). By considering two possible cases when electric yoyo flows can be induced within a return circuit, the paper uses specific examples to compute yoyo potential differences, the forces needed to pull a conductive wire in a magnetic yoyo field, and the total flux of magnetic yoyo field passing through a return circuit. When the paper tries to address the questions of how an electric yoyo current in a circuit is produced and what force could get around the resistance of metals to make electric yoyo charges move around inside return circuits, the paper successfully establishes a theoretical explanation for why Lenz's law about the direction of induced electric currents holds true. At the end, the paper develops a quantitative formula for practically calculating desired MMF.

Originality/value

This paper provides the first ever theoretical explanation for why Lenz's law could be true. It is expected that this explanation would be equally applicable in the study of social systems.

Details

Kybernetes, vol. 39 no. 2
Type: Research Article
ISSN: 0368-492X

Keywords

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Article
Publication date: 24 July 2019

Mustafa Kadıoğlu and Ertuğrul Durak

The purpose of this study was to examine the effect of the magnetic field to the friction coefficient in the rolling element bearings which exists in electric motors.

Abstract

Purpose

The purpose of this study was to examine the effect of the magnetic field to the friction coefficient in the rolling element bearings which exists in electric motors.

Design/methodology/approach

To achieve this, the test rig was modified to adjust the density of the magnetic flux applied to the rolling ball element bearing. Experiments were carried out in the magnetic field from 0 to 7.5 mTesla at magnetic flux density range from 15, 40 and 65 N constant loads. Also, its rotary speed selected as 100, 200, 400, 800 to 1200 rpm, respectively.

Findings

In the majority of the experiments, it was observed that the magnetic field affected the friction coefficient. This influence reduced the friction coefficient in some experimental conditions and increased in some of them.

Originality/value

In the literature, there are very few studies on the effect of magnetic flux density to the friction coefficient in these rolling element bearings. It has become clear that more studies have been conducted on the effects of the magnetic field and/or electrical current on bearing damages and failures. This aspect is a study with specificity.

Details

Industrial Lubrication and Tribology, vol. 71 no. 10
Type: Research Article
ISSN: 0036-8792

Keywords

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Article
Publication date: 24 August 2018

Piotr Jankowski and Miroslaw Woloszyn

The purpose of this paper is to present computer simulations of ship’s magnetic signatures using a new thin plate boundary condition implemented in the Opera 3D 18R2…

Abstract

Purpose

The purpose of this paper is to present computer simulations of ship’s magnetic signatures using a new thin plate boundary condition implemented in the Opera 3D 18R2 programme. This paper aims to check the magnetic signatures’ numerical calculations precision of objects using the thin plate boundary conditions and analysis of the magnetic signature of ship with a degaussing system and with and without inner devices.

Design/methodology/approach

The ferromagnetic sphere and cube with and without the thin plate boundary condition were compared. The computer results of the magnetic field of a sphere were compared with an analytical solution. A superstructure, decks, hull and bulkheads of a corvette were modeled. An analysis of ship’s magnetic field with consideration of inner ferromagnetic devices and with degaussing system was carried out.

Findings

The results of the analytical and numerical comparative analysis of magnetic field of cube and sphere have shown that the thin plate boundary condition is a good method for analysis of magnetic signatures of thin-walled objects. The computer simulations of the corvette model have shown that for relative magnetic permeability of a few hundred range the influence of inner ferromagnetic devices on the ship’s magnetic signature is negligible. The thin plate boundary condition is also good method for calculation of the ship magnetic signature with degaussing system and for optimization currents of coils.

Originality/value

The calculation time of ship’s magnetic field with the thin plate boundary condition bears resemblance to the ship model with layers of steel.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 37 no. 5
Type: Research Article
ISSN: 0332-1649

Keywords

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Article
Publication date: 18 May 2021

Mojtaba Sepehrnia, Hossein Khorasanizadeh and Mohammad Behshad Shafii

This paper aims to study the thermal and thermo-hydraulic performances of ferro-nanofluid flow in a three-dimensional trapezoidal microchannel heat sink (TMCHS) under…

Abstract

Purpose

This paper aims to study the thermal and thermo-hydraulic performances of ferro-nanofluid flow in a three-dimensional trapezoidal microchannel heat sink (TMCHS) under uniform heat flux and magnetic fields.

Design/methodology/approach

To investigate the effect of direction of Lorentz force the magnetic field has been applied: transversely in the x direction (Case I);transversely in the y direction (Case II); and parallel in the z direction (Case III). The three-dimensional governing equations with the associated boundary conditions for ferro-nanofluid flow and heat transfer have been solved by using an element-based finite volume method. The coupled algorithm has been used to solve the velocity and pressure fields. The convergence is reached when the accuracy of solutions attains 10–6 for the continuity and momentum equations and 10–9 for the energy equation.

Findings

According to thermal indicators the Case III has the best performance, but according to performance evaluation criterion (PEC) the Case II is the best. The simulation results show by increasing the Hartmann number from 0 to 12, there is an increase for PEC between 845.01% and 2997.39%, for thermal resistance between 155.91% and 262.35% and ratio of the maximum electronic chip temperature difference to heat flux between 155.16% and 289.59%. Also, the best thermo-hydraulic performance occurs at Hartmann number of 12, pressure drop of 10 kPa and volume fraction of 2%.

Research limitations/implications

The embedded electronic chip on the base plate generates heat flux of 60 kW/m2. Simulations have been performed for ferro-nanofluid with volume fractions of 1%, 2% and 3%, pressure drops of 10, 20 and 30 kPa and Hartmann numbers of 0, 3, 6, 9 and 12.

Practical implications

The authors obtained interesting results, which can be used as a design tool for magnetohydrodynamics micro pumps, microelectronic devices, micro heat exchanger and micro scale cooling systems.

Originality/value

Review of the literature indicated that there has been no study on the effects of magnetic field on thermal and thermo-hydraulic performances of ferro-nanofluid flow in a TMCHS, so far. In this three dimensional study, flow of ferro-nanofluid through a trapezoidal heat sink with five trapezoidal microchannels has been considered. In all of previous studies, in which the effect of magnetic field has been investigated, the magnetic field has been applied only in one direction. So as another innovation of the present research, the effect of applying magnetic field direction (transverse and parallel) on thermo-hydraulic behavior of TMCHS is investigated.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 31 no. 7
Type: Research Article
ISSN: 0961-5539

Keywords

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