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 Influence of Magnetic Field on the Peristaltic Flow of a Viscous Fluid through a Finite-Length Cylindrical Tube

2010 ◽  
Vol 7 (3) ◽  
pp. 169-176 ◽  
Author(s):  
S. K. Pandey ◽  
Dharmendra Tripathi
Keyword(s):  
Magnetic Field ◽  
Viscous Fluid ◽  
Transverse Magnetic Field ◽  
Finite Length ◽  
Flow Rate ◽  
Hartmann Number ◽  
Volume Flow Rate ◽  
Critical Value ◽  
Transverse Magnetic ◽  
Volume Flow

The paper presents an analytical investigation of the peristaltic transport of a viscous fluid under the influence of a magnetic field through a tube of finite length in a dimensionless form. The expressions of pressure gradient, volume flow rate, average volume flow rate and local wall shear stress have been obtained. The effects of the transverse magnetic field and electrical conductivity (i.e. the Hartmann number) on the mechanical efficiency of a peristaltic pump have also been studied. The reflux phenomenon is also investigated. It is concluded, on the basis of the pressure distribution along the tubular length and pumping efficiency, that if the transverse magnetic field and the electric conductivity increase, the pumping machinery exerts more pressure for pushing the fluid forward. There is a linear relation between the averaged flow rate and the pressure applied across one wavelength that can restrain the flow due to peristalsis. It is found that there is a particular value of the averaged flow rate corresponding to a particular pressure that does not depend on the Hartmann number. Naming these values ‘critical values’, it is concluded that the pressure required for checking the flow increases with the Hartmann number above the critical value and decreases with it below the critical value. It is also inferred that magneto-hydrodynamic parameters make the fluid more prone to flow reversal. The conclusion applied to oesophageal swallowing reveals that normal water is easier to swallow than saline water. The latter is more prone to flow reversal. A significant difference between the propagation of the integral and non-integral number of waves along the tube is that pressure peaks are identical in the former and different in the latter cases.

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.

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

ENTANGLEMENT MODULATION IN A SPIN CHAIN BY A LOCAL IMPURITY

2008 ◽  
Vol 06 (supp01) ◽  
pp. 567-573 ◽  
Author(s):  
TONY J. G. APOLLARO ◽  
ALESSANDRO CUCCOLI ◽  
ANDREA FUBINI ◽  
FRANCESCO PLASTINA ◽  
PAOLA VERRUCCHI
Keyword(s):  
Magnetic Field ◽  
Ground State ◽  
Spin Chain ◽  
Nearest Neighbor ◽  
Magnetic Impurity ◽  
Transverse Field ◽  
Transverse Magnetic ◽  
Spatial Modulation ◽  
Spin Pairs ◽  
The Magnetic Field

We study the ground-state entanglement properties of an XX spin 1/2 chain in transverse field, in its quasi-long-ranged ordered phase, with a magnetic impurity, represented in terms of an additional transverse magnetic field located at one precise site. For such a system, we show that a control of the ground state entanglement can be achieved by acting on the impurity field. To demonstrate this possibility, we evaluate exactly the nearest neighbor and next-nearest neighbor concurrence in the presence of the impurity. It turns out that either an enhancement or a quenching of entanglement between selected spin pairs can be obtained by acting on the intensity of the impurity. For specific values of the magnetic field a spatial modulation of concurrence along the chain is also obtained.

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.

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