Magnetic Alignments of Ba-Ferrite Particles in Suspension

2007 ◽  
Vol 336-338 ◽  
pp. 1042-1045
Author(s):  
Jing Long Li ◽  
Saburo Sano ◽  
Jiang Tao Xiong ◽  
Fu Sheng Zhang ◽  
Zhong Ping Wang
Keyword(s):  
Magnetic Field ◽  
Transverse Magnetic Field ◽  
Transverse Magnetic ◽  
Distilled Water ◽  
Magnetic Orientation ◽  
Water Drainage ◽  
Slip Cast ◽  
High Degree ◽  
The Magnetic Field ◽  
Long Chains

Ba-ferrite particles were dispersed into distilled water to make stable slurry, which was then slip cast in transverse magnetic field. The water drainage from the slurry was performed by vacuum evacuation to solidify the slurry into a cake – like sample. To obtain high degree of alignments, the slurries were slip cast in static – / pulsed – magnetic field and by using two separate steps of magnetic orientation and drainage. The particles turned their faces to the magnetic field and formed long chains stacked immediately while the magnetic field was applied, of which high induction density led to high degree of alignments. It is necessary to correspond with the drainage, gravity and magnetism so as to suppress the tendency of distortion or cracking of the sample as the aligned long chains of the particles tend to break into pieces and cave in randomly, which eventually destroys the particle alignments.

Comparison of the Effects of Bias Voltage and Transverse Magnetic Field on the Macro-Particles Distribution on the Surface of TiN Films Prepared by Arc Ion Plating

2011 ◽  
Vol 337 ◽  
pp. 300-306
Author(s):  
Wen Chang Lang
Keyword(s):  
Magnetic Field ◽  
Transverse Magnetic Field ◽  
Field Intensity ◽  
Magnetic Field Intensity ◽  
Transverse Magnetic ◽  
Key Factor ◽  
Influence Parameter ◽  
Two Parameters ◽  
Influence Degree ◽  
The Magnetic Field

The object of this article is to make research on the influence of transverse magnetic field and pulse bias on macro-particles on the surface of film, find the systematic law and analyze the influence law and reasons of the two parameters (transverse magnetic field and pulse bias), according to the mechanism of arc spot movement and the interaction between macro-particles and plasma. Moreover, this article aims at seeking the most important influence parameter and comparing the effect of the two parameters. Research in this paper indicates that: the key factor is the magnetic field controlled arc spot movement, because the influence of magnetic field on reducing macro-particles is much larger than bias, and the influence degree of bias on macro-particles varies with the magnetic field intensity; action of bias is obvious under the condition of low magnetic field intensity, but as the magnetic field intensity increases, its action becomes weaker and weaker; besides, purification effect of bias on particles in larger size is better than on particles in smaller size.

Article

1998 ◽  
Vol 76 (7) ◽  
pp. 507-513
Author(s):  
O Bolina ◽  
J R Parreira
Keyword(s):  
Magnetic Field ◽  
Transverse Magnetic Field ◽  
Ground State ◽  
Linear Chain ◽  
Critical Value ◽  
Transverse Magnetic ◽  
The State ◽  
Xy Model ◽  
The Magnetic Field

We show that the ground state of the xy model (ferromagnetic orantiferromagnetic) in a transverse magnetic field h --- for any spin value, in any dimension --- is the state with all spins aligned antiparallel to the field when h is greater than some critical value hc. In particular, for the spin-1/2 linear chain, we study the behavior of correlations as functions of the magnetic field. PACS Nos.: 75.10Jm and 64.60.Cm

scholarly journals Further investigation of the velocity of propagation of light in vacuo in a transverse magnetic field

1940 ◽  
Vol 175 (960) ◽  
pp. 1-25 ◽  
Keyword(s):  
Magnetic Field ◽  
Transverse Magnetic Field ◽  
Transverse Magnetic ◽  
The Other ◽  
Velocity Of Light ◽  
Propagation Of Light ◽  
Leakage Field ◽  
Velocity Of Propagation ◽  
Set Up ◽  
The Magnetic Field

In a previous paper (1932) an attempt to measure the effect, if any, of a transverse magnetic field on the velocity of light in vacuo was described. No change greater than 1 part in 2 x 10 7 was found in a field of 18,000 oersted. As the Jamin interferometer used had certain drawbacks for an experiment of this kind, it was decided to set up a Michelson type of interferometer, the use of which might be expected to avoid some of these difficulties and increase the sensitivity. In particular, one of the interfering rays could be made to pass twice through the magnetic field, or, by means of auxiliary mirrors, a multiple of this, while the other interfering ray, being at right angles to the first, was well away from the vicinity of the main leakage field, which would have a compensating effect as far as any change in velocity was concerned.

Possible Use of Magnetic Fields in Determining Pore Geometry of Porous Media

1971 ◽  
Vol 11 (03) ◽  
pp. 223-228 ◽  
Author(s):  
C.I. Pierce ◽  
L.C. Headley ◽  
W.K. Sawyer
Keyword(s):  
Magnetic Field ◽  
Porous Media ◽  
Magnetic Fields ◽  
Transverse Magnetic Field ◽  
Field Intensity ◽  
Flow Rate ◽  
Transverse Magnetic ◽  
Conducting Fluid ◽  
Petroleum Reservoir ◽  
The Magnetic Field

Abstract Simplified models, consisting of single, circular channels and channels of different length and diameter in series and parallel combinations, are used in conjunction with the equations of Poiseuille and Hartmann to demonstrate the dependence of the rate of flow of mercury in the models on channel dimensions when the models are subjected to transverse magnetic fields. Experimental tests conducted on mercury-saturated, glass-bead packs and a natural rock sample show that a magnetic field applied transversely to the direction of flow retards flow rate. The magnitude of the magnetic effect increased with increasing bead size and field intensity. Results of this work suggest that magnetic fields have potential in the study of the internal geometry of flow channels in porous media. Introduction The purpose of this work is to determine qualitatively by theoretical and experimental considerations whether or not a magnetic method has potential in the study of the basic properties of rock. The nature of the solid surface and the geometry of the pore network in petroleum-bearing rock plays an important role in the flow behavior of fluids in a petroleum reservoir. Hence, any technique of study that would provide new and additional information on the rock matrix would contribute to a better understanding of petroleum reservoir performance. One such technique appearing to offer performance. One such technique appearing to offer promise is in the area of magnetohydrodynamics. promise is in the area of magnetohydrodynamics. While much research, both theoretical and experimental, has been devoted to the problems concerned with the flow of conducting fluids in transverse magnetic fields in single channels, very little information has been published regarding the behavior of conducting liquids in porous media under the influence of a transverse magnetic field. Perhaps this dearth of information can be attributed Perhaps this dearth of information can be attributed to two main causes:the pores and pore connections are generally so small that intense magnetic fields are required to produce Hartmann numbers of sufficient magnitude to exert appreciable influence on flow rate, andthe extreme complexity of the channel systems in porous media render them intractable to theoretical analysis unless numerous assumptions are made to simplify network geometry. When a conducting fluid moves in a channel in a transverse magnetic field, a force is exerted on the fluid which retards its flow. The magnitude of flow-rate retardation increases with increasing field intensity, channel dimensions and channel-wall conductivity. These magnetohydrodynamic phenomena and theory have been described and developed by various investigators. Since a petroleum reservoir rock is an interconnected network of pores and channels within a rock framework, one would anticipate that the geometry of the network would exert some influence on the magnitude of the effect of a transverse magnetic field on the rate of flow of a conducting fluid therein. The purpose of this work is to demonstrate through the use of simple models and experimental data that the magnetic field effect on flow rate has potential for use in determining size and size potential for use in determining size and size distribution of pores in porous materials. THEORY Electromagnetic induction in liquids is not completely defined, and the complexities involved in many cases appear to defy true analytical expression. However, by applying some simplifying assumptions, these cases may be made tractable to solution to provide qualitative indication of system behavior. The following analysis was conducted in conjunction with laboratory tests to determine if magnet ohydrodynamics has possible potential as a tool for studying the internal geometry of porous systems. When a conducting liquid moves in a channel in a transverse magnetic field, an emf is developed in the channel normal to both the channel axis and the magnetic field. This emf causes circulating currents to flow in the liquid as shown in Fig. 1. SPEJ P. 223

Control of Vortex Shedding From a Bluff Body Using Imposed Magnetic Field

2006 ◽  
Vol 129 (5) ◽  
pp. 517-523 ◽  
Author(s):  
Sintu Singha ◽  
K. P. Sinhamahapatra ◽  
S. K. Mukherjea
Keyword(s):  
Magnetic Field ◽  
Reynolds Number ◽  
Steady Flow ◽  
Transverse Magnetic Field ◽  
Vortex Shedding ◽  
Bluff Body ◽  
Reynolds Numbers ◽  
Transverse Magnetic ◽  
Staggered Grid ◽  
The Magnetic Field

The two-dimensional incompressible laminar viscous flow of a conducting fluid past a square cylinder placed centrally in a channel subjected to an imposed transverse magnetic field has been simulated to study the effect of a magnetic field on vortex shedding from a bluff body at different Reynolds numbers varying from 50 to 250. The present staggered grid finite difference simulation shows that for a steady flow the separated zone behind the cylinder is reduced as the magnetic field strength is increased. For flows in the periodic vortex shedding and unsteady wake regime an imposed transverse magnetic field is found to have a considerable effect on the flow characteristics with marginal increase in Strouhal number and a marked drop in the unsteady lift amplitude indicating a reduction in the strength of the shed vortices. It has further been observed, that it is possible to completely eliminate the periodic vortex shedding at the higher Reynolds numbers and to establish a steady flow if a sufficiently strong magnetic field is imposed. The necessary strength of the magnetic field, however, depends on the flow Reynolds number and increases with the increase in Reynolds number. This paper describes the algorithm in detail and presents important results that show the effect of the magnetic field on the separated wake and on the periodic vortex shedding process.

Magnetohydrodynamic duct flow in a uniform transverse magnetic field of arbitrary orientation

1971 ◽  
Vol 48 (3) ◽  
pp. 429-461 ◽  
Author(s):  
C. J. N. Alty
Keyword(s):  
Magnetic Field ◽  
Pressure Gradient ◽  
Transverse Magnetic Field ◽  
Potential Distribution ◽  
Transverse Magnetic ◽  
Arbitrary Orientation ◽  
Axial Pressure Gradient ◽  
Viscous Shear ◽  
The Magnetic Field ◽  
Pressure Driven

The paper presents an approximate analysis for high Hartmann number of the flow of an electrically conducting, incompressible fluid in a duct of square crosssection, having one pair of opposite walls insulating, and the other pair perfectly conducting and inclined at arbitrary orientation to a uniform transverse magnetic field. The flow is considered to be either pressure-driven with the two perfectly conducting electrodes short-circuited together or electrically driven by a potential difference applied between these electrodes in the absence of axial pressure gradient. The paper describes experiments on the pressure-driven, short circuited case using mercury in copper ducts to investigate the variation of the streamwise pressure gradient and of the potential distribution along one insulating wall with orientation, magnetic field and flow rate.At general orientations the analysis suggests and the experiments confirm the existence of regions of stationary fluid in the corners of the duct, together with viscous shear layers parallel to the magnetic field. For the case in which the electrodes are parallel to the magnetic field the experimental results for the pressure gradient, but not those for the potential distribution, agree reasonably well with Hunt & Stewartson's (1965) asymptotic solution. Both pressure gradient and potential results agree closely with the analysis by Hunt (1965) of the case in which the electrodes are perpendicular to the magnetic field.

Numerical Investigation of the Transient Hydrothermal Behavior of a Ferrofluid Flowing Through a Helical Duct in the Presence of Nonuniform Magnetic Field

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Habib Aminfar ◽  
Mousa Mohammadpourfard ◽  
Sajjad Ahangar Zonouzi
Keyword(s):  
Magnetic Field ◽  
Transverse Magnetic Field ◽  
Magnetic Field Intensity ◽  
Control Volume ◽  
Transverse Magnetic ◽  
Uniform Heat Flux ◽  
Two Phase ◽  
Helical Channel ◽  
And Control ◽  
The Magnetic Field

This paper investigates numerically the time dependent hydrothermal behavior of a ferrofluid (water and 4 vol. % Fe3O4) flowing in a helical channel, which is exposed to a nonuniform transverse magnetic field and its walls are subjected to uniform heat flux. The two phase mixture model and control volume technique have been used to study the flow. The results show that applying the nonuniform transverse magnetic field considerably increases the velocity and flow rate in the vicinity of the channel walls while it significantly decreases the velocity at the center of the channel. Applying magnetic field also decreases considerably the temperature of the inner wall of the helical channel. Furthermore, the average Nusselt number is increased by applying the nonuniform transverse magnetic field and it is more enhanced by increasing the magnetic field intensity.

Highly Accurate Solutions of a Laminar Square Duct Flow in a Transverse Magnetic Field With Heat Transfer Using Spectral Method

2005 ◽  
Vol 128 (4) ◽  
pp. 413-417 ◽  
Author(s):  
Mohammed J. Al-Khawaja ◽  
Mohammed Selmi
Keyword(s):  
Magnetic Field ◽  
Velocity Profile ◽  
Spectral Method ◽  
Transverse Magnetic Field ◽  
Circular Tube ◽  
Transverse Magnetic ◽  
Duct Flow ◽  
Square Duct ◽  
Circular Pipe Flow ◽  
The Magnetic Field

A liquid metal forced-convection fully developed laminar flow inside a square duct, whose surfaces are electrically insulated and subjected to a constant temperature in a transverse magnetic field, is solved numerically using the spectral method. The axial momentum, induction, and nonlinear energy equations are solved by expanding the axial velocity, magnetic field, and temperature in double Chebyshev series and are collocated at Gauss points. The resulting system of equations is solved numerically by Gauss elimination for the expansion coefficients. The velocity and the magnetic field coefficients are directly solved for, while the temperature coefficients are solved for iteratively. Results show that the velocity profile is flattened in the direction of the magnetic field, but it is more round in the direction normal to it, in a similar fashion to the case of circular tube studied previously. The powerful spectral method resolves the sharp velocity gradient near the duct walls very well leading to accurate calculation of friction factor and Nusselt number. These parameters increase with the strength of the magnetic field due to the increasing flatness of the velocity profile. Comparison with the results for the circular tube shows that the effect of magnetic field on square duct flow is slightly lower from that one for circular pipe flow.

The annihilation of a two-dimensional jet by a transverse magnetic field

1967 ◽  
Vol 30 (1) ◽  
pp. 65-82 ◽  
Author(s):  
H. K. Moffatt ◽  
J. Toomre
Keyword(s):  
Magnetic Field ◽  
Reynolds Number ◽  
Transverse Magnetic Field ◽  
Magnetic Interaction ◽  
Transverse Magnetic ◽  
Magnetic Reynolds Number ◽  
Two Dimensional ◽  
Dimensionless Numbers ◽  
Order Unity ◽  
The Magnetic Field

The effect of an applied transverse magnetic field on the development of a two-dimensional jet of incompressible fluid is examined. The jet is prescribed in terms of its mass flux ρQ0 and its lateral scale d at an initial section x = 0. The three dimensionless numbers characterizing the problem are a Reynolds number R = Q0/ν, a magnetic Reynolds number Rm = μσQ0, and a magnetic interaction parameter N = σB20d2/ρQ0, where ρ represents density, σ conductivity, μ permeability and B0 applied field strength, and it is assumed that \[ R_m \ll 1,\quad R\gg 1,\quad N\ll 1. \] It is shown that when M2 = RN [Gt ] 1, an inviscid treatment is appropriate, and that the effect of the magnetic field is then to destroy the jet momentum within a distance of order N−1 in the downstream direction. A general solution for inviscid development is obtained, and it is shown that a large class of velocity profiles (though not all of them) are self-preserving.When M2 [Lt ] 1, it is shown that the viscous similarity solution obtained by Moreau (1963a, b) is relevant. This solution is re-derived and re-interpreted; it implies that the jet momentum is destroyed within a distance of order $R^{\frac{1}{4}}N^{-\frac{3}{4}}$ in the downstream direction.Some further aspects of the jet annihilation problem are qualitatively discussed in § 4, viz. the nature of the overall flow field, the effect of the presence of distant boundaries, the effect of increasing Rm to order unity and greater, and the effect of oblique injection. Finally the development of a jet of conducting fluid into a nonconducting environment is considered; in this case the jet is not stopped by the magnetic field unless a return path outside the fluid for the induced current is available.

Magneto-fluid-mechanic pipe flow in a transverse magnetic field Part 2. Heat transfer

1971 ◽  
Vol 48 (1) ◽  
pp. 129-141 ◽  
Author(s):  
R. A. Gardner ◽  
P. S. Lykoudis
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Transverse Magnetic Field ◽  
Pipe Flow ◽  
Transverse Magnetic ◽  
Uniform Heat Flux ◽  
Temperature Profiles ◽  
Velocity Fluctuations ◽  
Transfer Data ◽  
The Magnetic Field

The present paper, part 2, consists of an experimental investigation of the influence of a transverse magnetic field on the heat transfer of a conducting fluid (mercury) flowing in an electrically insulated pipe subjected to a uniform heat flux at the wall. Mean temperature profiles and heat transfer data are presented which demonstrate that the magnetic field inhibits the convective mechanism of heat transfer through its damping of the turbulent velocity fluctuations.

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