Uniform Magnetic Induction Research Articles

Film flow boiling of a magnetic fluid over a vertical plate exposed to a magnetic field under reduced gravity conditions

In this article, the film flow boiling over a vertical flat plate was studied numerically. The saturated liquid upward flow over a vertical flat plate with a uniform free stream velocity was considered. The Volume of Fluid (VOF) model was used for capturing the liquid-vapor interface. The effects of the wall superheat, the free stream velocity of hydrodynamics, and the heat transfer of the flow film boiling were studied in the absence and presence of a magnetic induction (MI). The results showed increased free stream velocity enhances the heat transfer coefficient (HTC). In addition, applying uniform MI results in a normal force at the liquid-vapor interface. This normal force enhances the local heat transfer coefficient (HTC) during film flow boiling on the heated vertical plate. Also, the percentage of HTC enhancement is higher when the magnetic field strength increases. Moreover, the heat transfer enhancement diminishes as the free stream velocity increases. Furthermore, an increase in the magnetic permeability ratios of the phases contributes to improving the HTC and increases the wall shear stress. The effect of the variation of the acceleration of gravity is also studied, revealing that a decrease in gravity’s acceleration actually slightly enhances HTC.

Magnetic field induced the assembling of Photothermal evaporator for efficient solar‐driven desalination

AbstractSolar‐driven interfacial evaporation is a sustainable and economical technology for freshwater generation. Structural design of photothermal material is an effective strategy to improve the evaporation performance but is usually bothered by complicated processes and non‐adjustability. Herein, magnetic nanoparticles assembled photothermal evaporator was developed, which showed an adjustable spinal array surface under uniform magnetic field induction. By regulating position in the magnetic field, the desirable surface structures could be uniform at relatively low load density of magnetic nanoparticles to improve light absorption via multiple reflections. Magnetic field induced evaporator could accelerate evaporation to over 1.39 kg m−2 h−1 under 1‐sun illumination, which was 2.8 times that of natural evaporation. After coated by carbon layer, magnetic nanoparticles could overcome the oxidation to realize stable evaporation in long‐term desalination. The facile strategy to optimize the surface structure via magnetic field is appropriate for various fields with special requirements on surface structure.image

Design and Simulation of a Magnetization Drive Coil Based on the Helmholtz Principle and an Experimental Study.

In order to realize the magnetization of hydrogel mixed with NdFeB powder, a magnetization drive coil based on a Helmholtz coil is designed in this paper. The 3D model of the magnetic field system is drawn by the Maxwell software 3D module, and the influence of different factors on the magnetic induction intensity is analyzed to obtain the optimized structure of the magnetization drive coil; then, the central magnetic induction intensity and magnetic induction line distribution density of the magnetization drive coil and Helmholtz coil are compared to verify the reliability of the structure optimization. The results show that the central magnetic induction intensity is the highest when the distance between the auxiliary coils is 70 mm, the central magnetic induction intensity of the magnetized drive coil is significantly higher than that of the Helmholtz coil when the number of turns is the same, and the central magnetic induction intensity of the optimized magnetized drive coil can reach 1.37 T with a more uniform and dense magnetic induction line distribution. After building the magnetization drive coil, the magnetic induction intensity of the center of the magnetization drive coil can reach 1.34 T by a handheld digital Gauss meter test, and the error is no more than 2% with the simulation result. This design approach provides a reference for the structural design and operating characteristics analysis of magnetized drive coils and shortens the design cost and development cycle of magnetized drive coils.

Several cracks in an orthotropic hollow cylinder coated by an MEE layer under torsion

This paper performs such fracture analysis for an orthotropic hollow cylinder coated by a magneto-electro-elastic (MEE) layer under torsion. The orthotropic hollow cylinder contains several arbitrarily shaped cracks. A uniform electric displacement and magnetic induction are applied on the outer boundary of the MEE coating. At first, the displacement and stress components of the coated hollow cylinder weakened by a Volterra-type screw dislocation are found as a function of the dislocation density through Fourier transform. Next, distributed dislocation technique (DDT) is used to simplify the stress components corresponding to the screw dislocation to a set of Cauchy singular integral equations. The singular integral equations are subsequently solved through a numerical procedure to obtain the unknown dislocation density. Next, the stress intensity factors (SIFs) and the torsional rigidity in the cracked hollow cylinder with its MEE coating are found in terms of the dislocation density function. Several numerical results of the SIFs and torsional rigidity are provided to reveal the effects of the geometrical and physical parameters on fracture behavior. It is concluded that the SIFs can be minimized using suitable values of the electric displacement and magnetic induction.

Conduction-Cooled Superconducting Magnet for Active-Target TPC Experiments at RAON

A compact superconducting magnet was constructed for low-energy nuclear physics experiments at the RAON heavy-ion accelerator facility. Conduction-cooled Helmholtz coils with a radius of 40 cm generate a uniform magnetic field of up to 1.51 Tat a current of 71 A. The magnet has two crossing beam windows that allows the beam to pass either parallel (solenoid mode) or perpendicular (dipole mode) to the field direction. The magnet operates at a ramping rate of 0.01 A/s without quenching and generates a highly uniform magnetic induction within 0.1% of the central value of 1.51 T over the volume of 10 × 10 × 10 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> corresponding to the size of an active target time projection chamber. Herein, we report our first excitation test and field mapping results.

Effects of uniform magnetic induction on heat transfer performance of aqueous hybrid ferrofluid in a rectangular cavity

Utilization of hybrid nanoparticles to formulate nanofluids is one of the ways to improve nanofluids’ thermal and fluid properties. This work attempted to study the free convection heat transfer performance of aqueous Fe2O3-Al2O3 (75:25) nanofluids in a rectangular cavity under magnetic induction. The thermal properties of the aqueous hybrid ferrofluids (AHFs) were measured for volume concentrations of 0.05–0.3 vol% and temperatures of 20–40 °C. Also, the stability and morphology of AHFs were examined. On charging the AHF and base fluid samples into the cavity, the two opposite vertical walls were subjected to temperature gradients ranging from 20 to 35 °C to create buoyancy. Parameters such as Nuav, hav, Ra and Qav were determined for each AHF sample and the base fluid. The AHF with the highest heat transfer performance was exposed to magnetic induction to investigate its convective heat transfer. With Ra range of 1.65 × 108–3.80 × 108, the Nuav was observed to intensify with increasing Ra. Without the magnetic induction, the improvements in hav, Nuav, and Q̇av were observed for 0.05–0.2 vol% AHFs in comparison with the base fluid. Optimum heat transfer enhancement of 10.79% was achieved for 0.10 vol% HF at ΔT = 35 °C. By inducing magnetic field (118.4 G) vertically on the side wall of the cavity, a maximum enhancement of Nuav (4.91%) was achieved compared to the case without magnetic induction. Additionally, increasing the magnetic field strength (48.9–219.5 G) was noticed to further enhance heat transfer of 0.10 vol% AHF. Correlations were proposed for predicting viscosity, thermal conductivity and Nuav of AHF in a rectangular cavity. The use of hybrid nanofluid was revealed to have better heat transfer performance than mono-particle nanofluids. Conclusively, the heat transfer performance was observed to depend on φ, ΔT, AHF deployment, magnetic induction, strength and direction.

Magnetoelastic stresses in a three-phase composite cylinder subject to a uniform magnetic induction

A solution of magnetoelastic stresses on a three-phase composite cylinder subjected to a remote uniform magnetic induction is derived in this study. Based upon the complex variable theory and the method of analytical continuation together with alternating technique, the general expressions of both the magnetic and the magnetoelastic field quantities can be obtained. The variations of the magnetoelastic stress on various parameters are displayed in graphic form. Comparisons between the results of this work and the existing solutions in literature under special cases reveal that the present solution is correct and general.

Explicit solutions of magnetoelastic fields in a soft ferromagnetic solid with curvilinear cracks

The problem of curvilinear cracks lying on a soft ferromagnetic solid subjected to a remote uniform magnetic induction is considered. With the complex variable technique, the general solutions of both the magnetic field quantities and the magnetoelastic stresses can be obtained. In order to illustrate the effect of magnetic induction, the solutions for the problem with one arc crack and two arc cracks are presented in a closed form. The stress intensity factors in the vicinity of crack tip and the crack opening condition are also derived. Considering the magnetic stress induced by an oblique magnetic field on the crack surface, one can find that the stress intensity factors of mode-I and mode-II are related to the incident angle of magnetic induction, the crack half angle and the magnetic susceptibility as displayed with figures. It is noticed that the present work is available even for a ferromagnetic material with low susceptibility. For the limiting case of the crack half angle in the one arc crack problem approaching to zero, the stress intensity factors are also provided and analytically compared with the existing ones of the straight crack problem.

The Magnetoelastic Problem for a Soft Ferromatnetic Elastic Half-Plane with a Crack and a Constant Magneic Induction

AbstractThe stress state of a magnetized elastic half-plane with a uniformly pressurized crack parallel to the free surface subjected to a uniform magnetic induction Bo is considered. The linear theory for a soft ferromagnetic elastic solid with muti-domain structure, which has been developed by Pao and Yeh [1] is adopted to investigate this problem. A numerical method is developed to determine the magnetoelastic stress intensity factor. The effect of the magnetic field and the boundary conditions on the magnetoelasitc stress intensity factor are shown graphically and numerically.

Magnetoelastic stresses in a soft ferromagnetic solid with a hole of arbitrary shape subject to uniform magnetic induction

An analytical solution for the magnetoelastic problem of an infinite soft ferromagnetic material with a hole of arbitrary shape is provided in this paper. Using the method of complex variable, such as conformal mapping technique and the analytic continuation, both the magnetic fields and magnetoelastic stresses can be obtained. Explicit solutions of several examples are also provided. Comparison with the degenerate case, such as a crack of which the analytic solutions were provided in the literature, is made to assure that the solution of the present work is general and exact. Numerical results for the tangential magnetoelastic stresses on the surface of an elliptic hole or a hypotrochoidal hole are displayed in graphic form to elucidate the effect of geometry parameters. Moreover, the stress intensity factors with r−1/2 singularity on the crack tip are also derived.

Evolution of free‐boundaries conduction into a superconductor sphere in magnetic variable field

PurposePresents a study of a bulk superconductor sphere placed in a uniform magnetic induction field b0(t).Design/methodology/approachAdapts some macroscopic laws for the numerical simulation of its evolution. This evolution is determinated by the front tracking method (FTM).FindingsThe deduction of some consequences concerning hysteresis losses, and comparison to a direct method are done.Originality/valueHelps to solve some complex three‐dimensional eddy current problems in industrial devices.

Growth and structure of CdZnTe crystal from Te solution with THM technique under static magnetic field

CdZnTe single crystal has been grown on CdTe substrate from Te solution with a traveling heater method under uniform static magnetic induction of 3 T. The growth experiments were carried out with growth rate of 4–10 mm/day and with temperature of 700– 800 ∘ C . The experimental results indicated that applying 3 T obviously improved the morphology of the growth interface in the crystal because of damping effect of the Lorentz force in Te solution, and that improvement of growth interface was beneficial to improve crystal micro-structure of CdZnTe .

Solutions for curvilinear cracks in bonded dissimilar materials subject to uniform magnetic induction

The magnetoelastic problem of curvilinear cracks lying along the interface between two dissimilar ferromagnetic materials under remote uniform magnetic induction is considered. On the basis of the Hilbert formulation and a special technique of analytical continuation, the solutions of the magnetic and the magnetoelastic stress fields either in the matrix or in the inclusion are expressed in a general form. Just like the pure elastic problem of curved cracks or the magnetoelastic problem of straight cracks in bonded dissimilar media, the trig-log character for the singularity of magnetoelastic stresses is found in this paper. Both the explicit solutions and the numerical results for the illustrating case of a single circular-arc crack in bi-material plate with typical ferromagnetic materials are given to elucidate the use of the present study. It is noted that the stress intensity factors are obtained and verified by comparison with the existing ones under special cases. The validity of the crack opening condition is also discussed.

Analytical solutions to magneto-electro-elastic beams

By means of the two-dimensional basic equations of transversely isotropic magneto-electro-elastic media and the strict differential operator theorem, the general solution in the case of distinct eigenvalues is derived, in which all mechanical, electric and magnetic quantities are expressed in four harmonic displacement functions. Based on this general solution in the case of distinct eigenvalues, a series of problems is solved by the trial-and-error method, including magneto-electro-elastic rectangular beam under uniform tension, electric displacement and magnetic induction, pure shearing and pure bending, cantilever beam with point force, point charge or point current at free end, and cantilever beam subjected to uniformly distributed loads. Analytical solutions to various problems are obtained.

Magnetoelastic stresses in a circular shell subject to a point magnetic source

The magnetoelastic problem of a circular shell subjected to the magnetic loadings is considered. In this paper the magnetic loadings include a point magnetic source in the domain outside or inside the circular shell or a uniform magnetic induction applied at infinity. Based upon the complex variable theory and the method of analytical continuation, the solutions of magnetic field quantities and the tangential magnetoelastic stresses in the shell and its outer and inner regions are obtained. The tangential magnetoelastic stresses for a thin shell in air under different magnetic loadings are also provided and compared with some special case of which the solution can be found in the literature, which reveals that the present solution is exact and general.

On a bounded elliptic elastic inclusion in plane magnetoelasticity

The problem of an elliptic inclusion embedded in an infinite matrix subjected to a uniform magnetic induction is considered in this paper. Basing upon the two-dimensional magnetoelastic formulation, the technique of conformal mapping, and the method of analytical continuation, a general solution of magnetic field quantities and the magnetoelastic stresses are obtained for both the matrix and the inclusion. Comparison is made with several special cases of which the analytical solutions can be found in the literature, which shows that the solutions presented here are general and exact. Moreover, the magnetoelastic stresses at the interface between the inclusion and the matrix are presented with figures.

Fundamental solutions for transversely isotropic magnetoelectro-elastic media and boundary integral formulation

To obtain the fundamental solutions for computation of magneto-electro-elastic media by the boundary element method, the general solutions in the case of distinct eigenvalues are derived and expressed in five harmonic functions from the governing equations and the strict differential operator theorem. On the basis of these general solutions, the fundamental solution of infinite magneto-electro-elastic solid are obtained with the method of trial-and-error. Finally, the boundary integral formulation is derived and the corresponding boundary element method program is implemented to perform two numerical calculations (a column under uni-axial tension, uniform electric displacement or uniform magnetic induction, an annular plate simply-supported on outer and inner surfaces under axial loads). The numerical results agree well with the analytical ones.

The magnetoelastic problem of cracks in bonded dissimilar materials

Abstract In this paper we consider the magnetoelastic problem of straight cracks lying along interface of two dissimilar soft ferromagnetic materials subjected to remote uniform magnetic induction. Based on the Hilbert problem formulation and the technique of analytical continuation, closed form solution for magnetic fields and both the magnetoelastic stresses and the Maxwell stresses are obtained. It is found that the singularity of magnetoelastic stresses has similar trig-log character as those obtained for pure elastic problems which were free from the discontinuous jumps of the magnetic properties and fields across the interface. For illustrating the use of present approach, the detailed results for a single crack case are provided and verified by comparison with the existing ones under special cases. The numerical examples of magnetoelastic stress distribution for different material properties are presented graphically. Expressions of the stress intensity factors in the vicinity of crack tip and crack opening condition are also derived. It is shown that the crack open assumption is valid except a limiting range of distance measured from the crack tip.

Spin echo three-axes spectrometers for improved energy and momentum resolution

Optimised Field Shape [1] spin precession coils can be made sufficiently short, so as to be added to existing Three-Axis Spectrometers (TAS) without increasing the neutron flight paths significantly. Furthermore, homogeneity corrections can be applied in such a way as to feature uniform magnetic induction line integrals even for very divergent beams. This way, intense TAS with Spin Echo combinations can be built, the loss of luminosity with respect to the normal polarised mode being negligible. Based on the experience with resistive TAS and Spin Echo spectrometers (TASSE) on PONTA (ISSP) and a superconducting version on IN20 (ILL) used mainly for high momentum transfer quasielastic scattering experiments (μeV–neV resolution), a variety of other applications will be made possible: inelastic scattering from excitations with μeV resolution and very high momentum transfer resolution (10 −3 Å −1), a domain until now reserved for synchrotron radiation. The fields of application will include the extension of the accessible momentum transfer region with respect to cold neutron Spin Echo, for example in the study of glass and liquid dynamics phase transitions and slow dynamics in general. The advantage of thermal neutrons as well as of the TAS background spectrometer with a well-defined transmission function will allow addressing new subjects such as excitation lifetimes across the entire Brillouin zone. Dispersive excitations can be ‘ focused’ by the use of gradient coils that allow restoring the echo polarisation blurred by the dispersion. Another application of these gradient coils is improved momentum resolution for elastic scattering that allows TASSE to compete with synchrotron radiation facilities.

A comparison of 60 Hz uniform magnetic and electric induction in the human body

High-resolution computations of induced fields are used to assess equivalent source levels for human exposure to uniform low-frequency electric and magnetic fields. These results pertain to 60 Hz foot-to-head electric excitation of the body in three positions with respect to a ground plane, and to magnetic excitation by three orthogonal source orientations. All computations are based on an anatomically derived human body model composed of 1736 873 cubic voxels with 3.6 mm edges. The data for magnetic excitation are computed using a scalar potential finite difference (SPFD) method, while those for electric excitation are computed using a hybrid method based on the SPFD method coupled with a quasistatic finite difference time domain code. The data are analysed in two ways, using an induced current density threshold of . Firstly, the various field strengths required to produce a whole-body average current density magnitude equal to the threshold are derived for each configuration, and the associated current density levels in various organs and tissues are presented. It is found that the average current density magnitude values in at least one tissue group can be up to 3 (5) times greater than the whole-body average under electric (magnetic) excitation, and that the associated maximum values can be up to 46 (28) times greater than the whole-body average under electric (magnetic) excitation, for at least one source/body configuration. Secondly, the data are analysed from the opposite point of view, in which the source levels required to induce average or maximum induced current density magnitudes at the threshold level in specific tissue groups are determined. Evaluations such as the present one should prove useful in the development of protection standards, and are also expected to aid in the understanding of results from various animal and tissue culture studies.