Nonhomogeneous Magnetic Field Research Articles

Simulation of magnetohydrodynamic flows of liquid metals with heat transfer or magnetic stirring

AbstractWe discuss the effects of nonhomogeneous magnetic fields in liquid metal flows in two different configurations. In the first configuration, we briefly report the impact of fringing magnetic fields in a turbulent Rayleigh–Bénard convection setup, where it was shown that the global heat transport decreases with an increase of fringe‐width. The convective motion in regions of strong magnetic fields is confined near the sidewalls. In the second configuration, we numerically study the effects of an oscillating magnetic obstacle with different frequencies of oscillation on liquid metal flow in a duct. The Reynolds number is low such that the wake of the stationary magnetic obstacle is steady. The transverse oscillation of the magnet creates a sinusoidal time‐dependent wake reminiscent of the vortex shedding behind solid obstacles. We examine the behavior of the streamwise and spanwise components of the Lorentz forces as well as the work done by the magnets on the fluid. The frequency of the oscillation of the streamwise component of Lorentz force is twice that of the spanwise component as in the case of lift and drag on solid cylindrical obstacles. The total drag force and the energy transferred from the magnets to the fluid show a nonmonotonic dependence on the frequency of oscillation of the magnetic obstacle indicative of a resonant excitation of the sinusoidal vortex shedding.

A Framework for Simulation of Magnetic Soft Robots Using the Material Point Method

Simulation represents a key aspect in the development of robot systems. The ability to simulate behavior of real-world robots provides an environment where robot designs can be developed and control systems optimized. Due to the use of external magnetic fields for actuation, magnetic soft robots can be wirelessly controlled and are easily miniaturized. However, the relationship between magnetic soft materials and external sources of magnetic fields present significant complexities in modelling due to the relationship between material elasticity and magnetic wrench (forces and torques). In this work, we present a simulation framework for magnetic soft robots using the Material Point Method (MPM) which integrates hyper-elastic material models with the magnetic wrench induced under external fields. Compared to existing Finite Element Methods (FEM), the presented MPM based framework inherently models self-collision between areas of the model and can capture the effect of forces in non-homogeneous magnetic fields. We demonstrate the ability of the MPM framework to model the influence of magnetic wrench on magnetic soft robots, capture dynamic behavior of robots under time-varying magnetic fields, and provide an accurate representation of deformation when colliding with obstacles. We show the versatility of MPM framework by comparing simulations to a range of real-world magnetic soft robot designs previously presented in the literature.

Dynamics of multiphase magnetic fluid systems in microchannels of different shapes in a nonhomogeneous magnetic field

We presented the results of a study of the dynamics of gas bubbles injected into a ferrofluid under the influence of an inhomogeneous magnetic field in microchannels of five configurations. The dependences of bubble sizes on the configuration of the magnetic field and the physical properties of the magnetic fluid are obtained. The results obtained can be used in gas meters and dispensers in microfluidics.

Dynamics of Multiphase Magnetic Fluid Systems in Microchannels of Different Shapes inside a Nonhomogeneous Magnetic Field

Dynamics of Multiphase Magnetic Fluid Systems in Microchannels of Different Shapes inside a Nonhomogeneous Magnetic Field

Magnetic force impact on melting behavior of dilatant non-Newtonian phase change materials using a numerical approach

This work proposes to explore how heat is transferred during melting dilatant non-Newtonian behaviour phase change materials (PCM) containing magnetic and ferro-hydrodynamic components in a differentially heated cavity. A dilatant non-Newtonian nano-encapsule phase change material (NEPCM) is used to fill the cavity, and a non-homogeneous magnetic field is placed around the heated wall. With the finite element method, equations are converted to a non-dimensional form in which solutions are found. A meshing deformation technique is used to trace the interface between the solid and liquid portions of the model. The findings of the grid research were compared to different studies in the literature and found to be in excellent accord. This study is dedicated to analyzing the phase change heat transfer and melting front effects of the power-law index (n = 1.1–1.5) and changeable parameters such as Rayleigh number (Ra = 103–106), Hartmann number (Ha = 0–200), and magnetic parameter (Mnf = 0–9000). The results demonstrate that increasing the Hartmann number decreases the melting process and increasing the magnetic parameter increases the melting process and the melting front becomes very non-linear as it gets to the cold wall. In addition, in research, it has been found that shear thickening fluids exhibit greater cooling capability. Finally, the average Nusselt number decreases with an increase in the non-Newtonian's index n and Hartmann number but increases with an increase in the magnetic parameter.

A Model of Water Treatment by Nanoparticles in a Channel with Adjustable Width under a Magnetic Field

The process of water treatment by nanoparticles is one of the most considerable subjects in the cross-field of hydrodynamics, chemistry, and mathematics. This paper is dedicated to the case of the flows that appear when squeezing and stretching a channel with mixing of water, nanoparticles, and contaminants. It is assumed that fluid is homogeneous at the starting moment, the parameters of the nanoparticles and contaminants are known, and there is a constant non-homogeneous magnetic field applied to the system. The flow starts moving when the walls of the channel shift to each other. Exact and numerical solutions of the system of ordinary differential equations are used to obtain the results. The article gives an answer to the question about stability of the flow and proposes the technique to evaluate the essential characteristics of the system to achieve the treatment process efficiency. The main result is that the considered system shows excellent properties concerning purification of water on the selected part of the squeezing stage. This effect does not appear without a magnetic field. The mentioned properties are: decreasing of nanoparticle concentration to zero inside of the unsteady layer under magnetic field close to 1 T and this effect stays until the channel become about 10% of initial width as a result of the squeezing.

Genetic-Algorithm-Based Optimization of a 3D Transmitting Coil Design with a Homogeneous Magnetic Field Distribution in a WPT System

In magnetically coupled resonant wireless power transfer (MCR-WPT) systems, the nonhomogeneous magnetic field of the transmitting coil can lead to frequency splitting phenomena and lower efficiency. In this paper, a 3D transmitting coil (TX) with a homogeneous magnetic field distribution is proposed. The proposed coil structure consists of two layers with different numbers of turns per layer, i.e., with different current distributions. To achieve a homogeneous magnetic field distribution with a high magnetic field value and a low profile of the 3D coil structure, the optimal layer placement and current distribution were optimized using a genetic algorithm (GA). The prototype of the optimized coil was fabricated, and its magnetic field distribution was measured. The measurement results agreed more than 95% with the simulation results. The measured homogeneous area was at least 12.5% larger than reported in the literature. By using a different current distribution, the profile of the 3D coil structure was successfully reduced by 29% and the average magnetic field value was increased by 25% compared to our previous work.

Kinetic theory of double layers driven by temperature anisotropy in a non-homogeneous magnetic field

A double layer (DL) is created in a plasma when the plasma is perturbed in the presence of a temperature anisotropy. We derive a new simple theory for the existence of an unstable, non-oscillatory electrostatic DL-like structure in the presence of a magnetic field gradient in a collisionless plasma with a temperature anisotropy in the direction perpendicular to the magnetic field. The DL is treated as a wave perturbation in the plasma using kinetic theory with a gyro-kinetic approximation to obtain a dispersion relation. The presence of an electron temperature anisotropy is the necessary condition to obtain an exponentially growing instability, and the corresponding growth rate is found to be the ratio of the electron kinetic energy and the electric field energy across the DL region. The theoretical predictions are then validated against a one-dimensional electrostatic particle simulation carried out in a traveling magnetic field thruster environment. An anisotropy ratio parameter was introduced, and the theoretical growth rates were found to be in good agreement with the simulation for different anisotropy ratios. An ion beam, associated with the DL dynamics, is observed within the simulation domain. A parametric study revealed that the DL-like structure loses its ambipolar shape for temperature ratios less than 10. It has been found that a stronger anisotropy is required to obtain the DL-like structure.

Real time display with the ferrolens of homogeneous magnetic fields

In our previous published research we have studied the applications of the ferrolens for the observation and qualitative analysis of non-homogeneous magnetic fields. Latest developments over the last few years of the ferrolens increased multifold the sensitivity of this device allowing it to display magnetic fields as low as 10mT in strength and therefore it is possible now to observe also the homogeneous (i.e. straight parallel magnetic flux lines of uniform density in space) magnetic field existing inside air solenoids and between N-S poles of two attracting separated permanent magnets. We present and analyze herein these novel observations of homogeneous magnetic fields with the ferrolens and as a potential new application of this device. The ferrolens can now display the projected magnetic field on air from a distance without needing to be in physical contact with the field source. Experiments were carried out to demonstrate these new capabilities of the ferrolens as a nanomagnetic flux viewer, real-time physical device and scientific qualitative tool. We compare the geometry of magnetic fields of condensed matter ferromagnets with that of magnetic fields inside electrical air solenoids. Specifically, the homogeneous field between two N-S attracting magnets at a distance as well as inside air solenoids and Helmholtz coils and also the non-homogeneous total field of single dipole permanent magnets were observed using a latest generation very sensitive ferrolens. The unique feature of this magneto optic fluid thin film physical device is that it can display discrete magnetic flux lines of the macroscopic field. Also we show how the ferrolens can be used to detect qualitatively the symmetry center of a non ideal homogeneous magnetic field.

Influence of inhomogeneous magnetic field on the qutrit teleportation via XXZ Heisenberg chain under intrinsic decoherence

We study qutrit teleportation through a qutritxxzchain, in the presence of intrinsic decoherence and a non-homogeneous magnetic field. We study the effects of intrinsic phase change, magnetic field and entanglement of the initial state of the channel. It is observed that while the intrinsic phase change and the non-homogeneity of the magnetic field have adverse effects on the teleportation fidelity, the entanglement of the initial state of the channel enhances the latter. Moreover, the intrinsic decoherence may remove the ripples from the time curve that is delivered by the Schrödinger channel.

Multi-Point Orientation Control of Discretely-Magnetized Continuum Manipulators

In the past decade, remote actuation through magnetic fields has been used for position and orientation control of continuum manipulators (CMs) with a single magnet at the distal tip. By leveraging multiple points of actuation along the length of the CM it is possible to achieve increasingly complex shapes, which could be of interest in complex navigation tasks, for example, in minimally invasive surgery. In this study we present an approach for multi-point orientation control of discretely magnetized CMs. The approach is demonstrated with a manipulator that contains two permanent magnets, which are each actuated inside a non-homogeneous magnetic field. We formulate an accurate field model that conforms to Maxwell's equations and apply this to the available actuation system. Furthermore, Cosserat rod theory is used to model the manipulator deformation under external wrenches, and is utilized to numerically compute a Jacobian necessary to calculate the actuation inputs. During experiments, a stereo vision setup is used for manipulator shape feedback. Target orientations are manually provided as input to show independent orientation control of the two permanent magnets. Additionally, simulations with an extended virtual clone of the electromagnetic system are performed to show the capability of achieving more complex manipulator shapes. In both scenarios, it is observed that the algorithm is able to independently control the orientation of two interconnected magnets in a non-uniform magnetic field.

Direct numerical simulation of magneto-Archimedes separation of spherical particles

Abstract

Метод сбора нефти в ледовых условиях с использованием магнитного поля и тонкодисперсного магнетита

The oil spill response using skimmer systems in the glacial seas continues to be relevant in world practice. A complex approach based on the combination of oil slick dispersion by solid fine magnetic particles and skimmer cleaning, the operative parts of which are equipped with metallic magnetized bristles, has been proposed as a promising and innovative solution. Application of finely dispersed magnetite – ferromagnetic spherical particles (iron oxides) as fine solid particles to create stable Pickering emulsions with formation of oil-ferromagnetic units is considered. Mathematical modeling has been performed to estimate the possibility of extraction of such oil-ferromagnetic units from water-oil emulsion under the influence of nonhomogeneous magnetic field created by magnetized steel bristles of skimmer operative parts. The results obtained confirmed the possibility of a practical application of the solution proposed by the authors to improve the efficiency of mechanical cleaning of oil spills in glacial seas.

Theory of magnetotransport in shaped topological insulator nanowires

We show that shaped topological insulator (TI) nanowires, i.e. such that their cross-section radius varies along the wire length, can be tuned into a number of different transport regimes when immersed in a homogeneous coaxial magnetic field. This is in contrast with widely studied tubular nanowires with constant cross-section, and is due to magnetic confinement of Dirac surface carriers. In flat 2D systems such a confinement requires non-homogeneous magnetic fields, while for shaped nanowires of standard size homogeneous fields of the order of $B\sim\,1$T are sufficient. We put recent work [Kozlovsky et al., Phys. Rev. Lett. 124, 126804 (2020)] into broader context and extend it to deal with axially symmetric wire geometries with arbitrary radial profile. A dumbbell-shaped TI nanowire is used as a paradigmatic example for transport through a constriction and shown to be tunable into five different transport regimes: (i) conductance steps, (ii) resonant transmission, (iii) current suppression, (iv) Coulomb blockade, and (v) transport through a triple quantum dot. Switching between regimes is achieved by modulating the strength of a coaxial magnetic field and does not require strict axial symmetry of the wire cross-section. As such, it should be observable in TI nanowires fabricated with available experimental techniques.

Static and optical anapole magnetizabilities and polarizabilities.

The anapolar response of a molecule exposed to a nonhomogeneous magnetic field B with spatially uniform curl C = ∇ × B is rationalized via second-rank tensors, a nonsymmetric aαβ, and a symmetric bαβ, referred to as static anapole magnetizabilities, which can be evaluated by quantum-mechanical Rayleigh-Schrödinger perturbation theory or allowing for the definitions of electronic current densities JB(r) and JC(r) induced in the electron cloud. The isotropic part of bαβ is even under the fundamental symmetry operations of charge conjugation C, parity P, and time reversal T and does not vanish for all matter and antimatter. The isotropic part of aαβ is even under C and T, but odd under P, and is exhibited only by chiral compounds. In the presence of optical fields, represented for simplicity by a monochromatic plane wave of frequency ω, dynamic anapole magnetizabilities and various anapole polarizabilities are taken into account. Assuming, within the electric quadrupole approximation for the impinging wave, that the electric field at the origin of the coordinate system is E(0), with uniform gradient ∇E, and magnetic field is B, the anapolar response is interpreted by second-rank aαβ(ω), aαβ '(ω), fαβ(ω), fαβ '(ω) and third-rank gα,βγ(ω), gα,βγ '(ω) frequency-dependent tensors. The same basic definitions are arrived at introducing frequency-dependent electronic current densities JB(r, ω) and JC(r, ω). As the frequency-dependent anapole susceptibilities depend on the origin of the coordinate system, relationships connecting them for two different origins are reported.

Young bilateral supernova remnants evolving into a turbulent interstellar magnetic field

ABSTRACT We employ 3D magnetohydrodynamic simulations to study the morphology and synchrotron emission of young supernova remnants evolving in a turbulent interstellar magnetic field, seeking to shed new light on to the polarization structure of the emission and on the debate concerning the quasi-parallel and quasi-perpendicular acceleration mechanisms. In the simulations, we consider a non-homogeneous interstellar medium magnetic field by introducing small random perturbations in the direction and intensity of the field. In order to analyse the dependence of the radio morphology on the degree of magnetic field perturbation and the observer’s point of view, we compute synthetic maps of the polarized intensity, position-angle, polarization fraction, and the polar-reference angle. By comparing the distribution of this angle to the polarization intensity, we show that it is possible to identify what type of acceleration mechanism is taking place at the main shock front.

Importance of Basset History Force for the Description of Magnetically Driven Motion of Magnetic Particles in Air

Abstract Lungs are used as an attractive possibility for administration of different therapeutic substances for a long time. An innovative method of such administration widely studied nowadays is the application of aerosolized magnetic particles as the carriers to the lungs in the external non-homogeneous magnetic field. For these reasons we have studied dynamics of such a system on a level of particle trajectory in air in the presence of magnetic force as a driving force exerted on micrometric magnetic particle. On two typical examples of magnetically driven systems—motion of magnetic particle in a gradient magnetic field and cyclotron-like motion of a charged particle in homogeneous magnetic field in microscale, where the external accelerating forces are very large and the relevant time scale is of the order from fraction of milliseconds to seconds, we have examined the importance of these forces. As has been shown, for particles with high initial acceleration, not only the commonly used Stokes force but also the Basset history force should be used for correct description of the motion.

Fabrication of calcium phosphate 3D scaffolds for bone repair using magnetic levitational assembly

The calcium phosphate particles can be used as building blocks for fabrication of 3D scaffolds intended for bone tissue engineering. This work presents for the first time a rapid creation of 3D scaffolds using magnetic levitation of calcium phosphate particles. Namely, tricalcium phosphate particles of equal size and certain porosity are used, which undergo the process of recrystallization after magnetic levitational assembly of the scaffold to ensure stitching of the scaffold. Label-free levitational assembly is achieved by using a custom-designed magnetic system in the presence of gadolinium salts, which allows the levitation of calcium phosphate particles. Chemical transformation of tricalcium- to octacalcium phosphate under the condition of magnetic levitation in non-homogeneous magnetic field is also demonstrated. This approach allows obtaining rapidly the octacalcium phosphate phase in the final 3D product, which is biocompatible.

Semi-active vibration control of MRF core PMC cantilever sandwich beams: Experimental study

The semi-active vibration control of sandwich beams made of chopped strand mat glass fiber reinforced polyester resin polymer matrix composite (PMC) and magnetorheological fluid (MRF) core were experimentally investigated in this study. Two-, four- and six-layered glass fiber reinforced polyester resin polymer matrix composites were prepared using the hand-layup technique. The magnetorheological fluid was prepared in-house with 30% volume of carbonyl iron powder and 70% volume of silicone oil. Nine cantilever sandwich beams of varying thicknesses of the top and bottom layers glass fiber reinforced polyester resin polymer matrix composite beams and middle magnetorheological fluid core were prepared. The magnetorheological fluid core was activated with a non-homogeneous magnetic field using permanent magnets. The first three modes, natural frequencies and damping ratios of the glass fiber reinforced polyester resin polymer matrix composite-magnetorheological fluid core sandwich beams were determined through free vibration analysis using DEWESoft modal analysis software. The amplitude frequency response of the glass fiber reinforced polyester resin polymer matrix composite-magnetorheological fluid core sandwich beams through forced vibration analysis was determined using LabVIEW. The effect of various parameters such as magnetic flux density, thickness of glass fiber reinforced polyester resin polymer matrix composite layers and magnetorheological fluid core layer on the natural frequencies, damping ratio and vibration amplitude suppressions of the glass fiber reinforced polyester resin polymer matrix composite-magnetorheological fluid core sandwich beams was investigated. Based on the results obtained, 2 mm thickness top and bottom layers glass fiber reinforced polyester resin polymer matrix composite and 5 mm thickness magnetorheological fluid core sample have achieved a high shift in increased natural frequency, damping ratio and vibration amplitude suppression under the influence of magnetic flux density.

GMR effect in nonhomogeneous magnetic field

Magnetic field sensors, based on giant magnetoresistance (GMR) effect, have a wide range of practical implementations. One of them is the use as a positioning device in different kind of actuators. Here we report on modelling of magnetoresistivity response of spin-valve (SV) based GMR structure in a various geometry of SV positioning with respect to a magnetic reference label. The model includes the magnetic label of a certain shape producing a nonhomogeneous magnetic field in 3D space and moving along a straight line in front of SV device. Different mutual label-SV positioning is considered. The reaction of micromagnetic configuration in the ferromagnetic layers and corresponding magnetoresistive effect of the SV is calculated and analyzed.