Effect Of Magnetic Field Orientation Research Articles

Magnetic field impact on ferronanofluid laminar flow

A comprehensive understanding of the magnetic field interaction with the flow of ferronanofluids is essential to determine the heat transfer effect and the potential for use in industrial applications. The purpose of this work is to determine the effects of magnetic field orientation and intensity, as well as inertia forces, on heat transfer in the laminar flow of a ferronanofluid. The experiment involved the use of five permanent magnets positioned both below and above the flowing magnetite-based ferronanofluid. The analysis of the effect on heat transfer is carried out using the similarity numbers, Reynolds number (ratio of inertia and viscous forces), magnetic number (ratio of magnetic and inertia forces) and product of the two (ratio of magnetic and viscous forces).The findings indicate that the orientation of the magnetic field relative to temperature gradient-induced secondary motions plays a crucial role in either enhancing or inhibiting heat transfer. The magnet positioned below the flow leads to improved heat transfer, while placement above hinders it. To determine the magnetic field effect on heat transfer, the ratio of magnetic to viscous force introduced as MnRe is used. Taking the 5 % Nusselt number change as the threshold, the critical value for the orientation of magnet above the tube is MnRe = 24,000, while for the configuration with the magnet below, MnRe = 32,000 for Re = 109 and MnRe = 88,000 for Re = 150 and 163. The magnetic field effect is local and diminishes as the fluid flows, ultimately causing the heat transfer parameters to revert to their reference state. However, an increase in the ratio of inertia and viscosity forces enables the magnetic field interaction effect to propagate over a longer distance.

Constraint-based analysis of heat transport and irreversibility in magnetic nanofluidic thermal systems

Purpose This paper aims to investigate the thermal performance of equivalent square and circular thermal systems and compare the heat transport and irreversibility of magnetohydrodynamic (MHD) nanofluid flow within these systems. Design/methodology/approach The research uses a constraint-based approach to analyze the impact of geometric shapes on heat transfer and irreversibility. Two equivalent systems, a square cavity and a circular cavity, are examined, considering identical heating/cooling lengths and fluid flow volume. The analysis includes parameters such as magnetic field strength, nanoparticle concentration and accompanying irreversibility. Findings This study reveals that circular geometry outperforms square geometry in terms of heat flow, fluid flow and heat transfer. The equivalent circular thermal system is more efficient, with heat transfer enhancements of approximately 17.7%. The corresponding irreversibility production rate is also higher, which is up to 17.6%. The total irreversibility production increases with Ra and decreases with a rise in Ha. However, the effect of magnetic field orientation (γ) on total EG is minor. Research limitations/implications Further research can explore additional geometric shapes, orientations and boundary conditions to expand the understanding of thermal performance in different configurations. Experimental validation can also complement the numerical analysis presented in this study. Originality/value This research introduces a constraint-based approach for evaluating heat transport and irreversibility in MHD nanofluid flow within square and circular thermal systems. The comparison of equivalent geometries and the consideration of constraint-based analysis contribute to the originality and value of this work. The findings provide insights for designing optimal thermal systems and advancing MHD nanofluid flow control mechanisms, offering potential for improved efficiency in various applications. Graphical Abstract

Enhancement of thermal conductivity of BN-Ni/epoxy resin composites through the orientation of BN-Ni fillers by magnetic field and hot-pressing

The construction of high thermal conductivity polymer composites by the orientation of fillers is of great significance in electronic devices. Herein, a novel strategy to prepare boron nitride-Ni nanoparticles/epoxy resin composites (hmBN-Ni/EP) through the synergistic effect of magnetic field and hot-pressing on the orientation of BN-Ni fillers has been reported. hmBN-Ni/EP composites have better BN orientation in the in-plane direction than other BN-based/EP composites obtained by hot-pressing or magnetic field orientation only. The thermal conductivity of hmBN-Ni/EP reached 2.42 W m−1 K−1 at 30 wt% BN-Ni loading, which was 1145% higher than pure EP. The enhancement of thermal conductivity of hmBN-Ni/EP was attributed to the high in-plane orientation of BN-Ni through the synergistic effect of magnetic field orientation and hot-pressing. Meanwhile, the as-prepared hmBN-Ni/EP composites showed good insulation and mechanical properties which were facilitated to its industrial application in electronic packaging. This work provided a new strategy for better orientation of BN-Based fillers in polymer matrix by combining the magnetic field orientation and hot-pressing.

The effect of magnetic field orientation on the magnetoimpedance of electroplated NiFeCo/Cu wire

The effect of magnetic field orientation on the magnetoimpedance of electroplated NiFeCo/Cu wire

Effect of magnetic field orientation on suppressing porosity in steady-magnetic-field-assisted aluminum alloy deep-penetration laser welding

The steady magnetic fields were utilized to decrease the porosity of aluminum alloy laser welded joints, and the effect is related to the magnetic field orientation. The influence of the magnetic field orientation on the suppression of porosity was investigated by establishing a three-dimensional heat flow model coupled with magnetohydrodynamics (MHD) and free surface of a keyhole. The Lorentz force decreased the backflow velocity toward the keyhole wall when the magnetic fields were horizontally parallel to the welding direction (magnetic field X-axis, MFX) and perpendicular to the welding direction (magnetic field Y-axis, MFY), thereby clearly improving the keyhole stability. Additionally, the melt flows in the rear region of the molten pool were suppressed downward and forward under the MFX and MFY, respectively, leading to additional heat accumulation in the rear periphery of the molten pool. As a result, a long molten pool in the longitudinal section and a small penetration depth were observed under the MFX and MFY. Therefore, the porosity defects decreased from 9.4% to 3.5% and 3.2% under the MFX and MFY, respectively. However, many pores were observed when the magnetic field orientation was vertical (magnetic field Z-axis, MFZ), owing to the high penetration depth and poor keyhole stability. This study provides a deeper understanding of the effect of magnetic fields on the laser welding of aluminum alloys and potentially lays a foundation for the adjustment of suitable magnetic field parameters toward obtaining the desired effect.

Magnetohydrodynamic simulations of binary neutron star mergers in general relativity: Effects of magnetic field orientation on jet launching.

Binary neutron star mergers can be sources of gravitational waves coincident with electromagnetic counterpart emission across the spectrum. To solidify their role as multimessenger sources, we present fully 3D, general relativistic, magnetohydrodynamic simulations of highly spinning binary neutrons stars initially on quasicircular orbits that merge and undergo delayed collapse to a black hole. The binaries consist of two identical stars modeled as Γ = 2 polytropes with spin χ NS = 0.36 aligned along the direction of the total orbital angular momentum L. Each star is initially threaded by a dynamical unimportant interior dipole magnetic field. The field is extended into the exterior where a nearly force-free magnetosphere resembles that of a pulsar. The magnetic dipole moment μ is either aligned or perpendicular to L and has the same initial magnitude for each orientation. For comparison, we also impose symmetry across the orbital plane in one case where μ in both stars is aligned along L. We find that the lifetime of the transient hypermassive neutron star remnant, the jet launching time, and the ejecta (which can give rise to a detectable kilonova) are very sensitive to the magnetic field orientation. By contrast, the physical properties of the black hole + disk remnant, such as the mass and spin of the black hole, the accretion rate, and the electromagnetic (Poynting) luminosity, are roughly independent of the initial magnetic field orientation. In addition, we find imposing symmetry across the orbital plane does not play a significant role in the final outcome of the mergers. Our results suggest that, as in the black hole-neutron star merger scenario, an incipient jet emerges only when the seed magnetic field has a sufficiently large-scale poloidal component aligned to the initial orbital angular momentum. The lifetime [Δt ≳ 140(M NS/1.625 M ⊙) ms] and Poynting luminosities [L EM ≃ 1052 erg/s] of the jet, when it forms, are consistent with typical short gamma-ray bursts, as well as with the Blandford-Znajek mechanism for launching jets.

EFFECT OF MAGNETIC FIELD ORIENTATION ON NANOFLUID FREE CONVECTION IN A POROUS CAVITY: A HEAT VISUALIZATION STUDY

Effect of magnetic field orientation on free convection of several water–based nanofluids in a square porous cavity is analyzed in this study. To this aim, the heatline visualization technique is implemented for the first time. Moreover, streamlines and isotherms are employed to present fluid flow and temperature distribution. The governing equations are transformed into a dimensionless form and then solved using the finite–volume method. Computations are undertaken for different orientations and magnitudes of the imposed magnetic field in circumstances with distinct Rayleigh numbers and the nanoparticles types and volume fractions. The corresponding results are presented in terms of dimensionless distributions of streamlines, isotherms, and heatlines as well as numerical values of the flow strength and the average Nusselt number. Inspection of the results demonstrates that increase in the magnetic field strength deteriorates the heat transfer rate. This effect, however, diminishes with rise in the magnetic field inclination angle.

Magnetohydrodynamic effects in a shock-accelerated gas cylinder

We numerically study the effect of magnetic field orientation and strength on a shock-accelerated gas cylinder susceptible to the Richtmyer-Meshkov instability. We find regimes where fluid mixing increases with field strength and a preferential field orientation for damping the instability.

Effect of magnetic-field orientation on dual-peak phenomenon of magnetoelectric coupling in Ni/PZT/Terfenol-D composites

Magnetoelectric (ME) effect in a Ni/PZT/Terfenol-D composite cantilever was tested under three different magnetic loading modes. The frequency-dependent ME effect and dual-peak phenomenon were observed in the experiment. The influence of orientations of magnetic fields on the dual-peak phenomenon of ME coupling was investigated. Magnetic field distribution inside the ME composite structure was simulated, which agrees well with experimental data. The experiment results indicate that ME coefficient versus bias magnetic field curve presents a novel dual-peak phenomenon near the resonant frequency, and the ME coefficient which depends upon the amplitude and orientation of magnetic field presents a nonlinear shift whether at the resonant frequency or not. In addition, the optimal angle corresponding to the largest ME coefficient for different bias fields were obtained. The proposed ME composites-based sensors can be used for detecting or harvesting magnetic signals of uncertain orientations and amplitudes in complex environments.

The effect of magnetic field orientation on the open-circuit voltage of Ni–Mn–Ga based power harvesters

Ni–Mn–Ga is a ferromagnetic alloy that can exhibit the shape memory effect or superelasticity in the presence of a magnetic field. The behavior of the material is largely due to its microstructure, which is thought to be made of tetragonal martensite variants, each exhibiting an innate magnetization aligned approximately with the short side of the unit cell. Because the reorientation strain can be induced and recovered by either magnetic field or mechanical stress, it can be induced at frequencies larger than 1 kHz, which makes the material suitable for high-frequency actuation, sensing, or power harvesting applications. This paper investigates the power harvesting capability of Ni–Mn–Ga wrapped with a pick-up coil under a bi-axial magnetic field. In this work, both experimental tests and numerical simulations are used to identify the optimal direction of the externally applied magnetic field in order to achieve maximum open-circuit voltage output from a particular Ni–Mn–Ga based power harvester. Results suggest that significantly more power can be achieved with the bias field applied at an angle of 10°–20° off the perpendicular to the coil axis and the compressive stress. We believe that this increased power output is due to the saturation of domain walls due to a small component of the magnetic field along the direction of the coil.

Effects of magnetic field orientation and strength on the treatment planning of nonsmall cell lung cancer.

Magnetic resonance image-guided radiotherapy (MRgRT) has the potential to increase the accuracy of radiation treatment delivery. Several research groups have developed hybrid MRgRT devices differing by radiation source used and magnetic field orientation and strength. In this work, we investigate the impact of different magnetic field orientations and strengths on the treatment planning of nonsmall cell lung cancer patients (NSCLC). A framework using the in-house developed treatment planning system matRad and the EGSnrc Monte Carlo code system was introduced to perform Monte Carlo-based treatment planning in the presence of a magnetic field. A specialized spectrum-based source model for the beam qualities of 6 MV and cobalt-60 was applied. Optimized plans for stereotactic body radiation therapy (SBRT) and intensity-modulated radiation therapy (IMRT) were generated for four NSCLC patients in the presence of different magnetic field orientations and strengths which are applied in hybrid MRgRT devices currently under development or in clinical use. SBRT and IMRT treatment planning could be performed with consistent plan quality for all magnetic field setups. Only minor effects on the treatment planning outcome were found in the case of magnetic fields orientated perpendicular to the beam direction. Compared to the perpendicular magnetic field orientation, the inline orientation showed the capability to reduce the dose to lung while maintaining equal target coverage. Particularly for tumors with a central position in lung, a distinct dose reduction was obtained which led to a maximum reduction of mean lung dose by 18.5% (0.5 Gy), when applying a 1 T inline magnetic field. All plans generated in this work obtained dose metrics within clinical constraints according to RTOG guidelines. When considering conventional dose metrics, no detrimental effects due to the magnetic fields were observed on the dose to the tumor or to organs at risk. An evaluation of the effects on skin dose was not ascertainable due to the simplified specification of the source model used. By accounting for the magnetic field during treatment planning, a dose reduction in lung could be achieved for inline-oriented magnetic fields. An inline orientation of the magnetic field therefore showed a potential benefit when treating NSCLC with MRgRT.

Ionospheric Langmuir Probe Electron Temperature Asymmetry and Magnetic Field Connectivity

Simulation results are presented, which demonstrate the effect of magnetic field orientation on electron temperature inferred from a planar Langmuir probe (PLP) near a physical object. PLP characteristics are calculated with two orientations of the magnetic field corresponding to: 1) magnetic field lines intersecting the PLP, also intersecting a physical object, and 2) field lines intersecting the PLP not intersecting any other physical object. In the first case, the PLP is referred to as being “magnetically connected” to another object, while in the second case it is “magnetically disconnected”. Characteristics computed for the PLP in these two cases are used to infer the electron temperature obtained using otherwise identical plasma parameters (electron and ion density and temperature, plasma flow velocity). Applying the same equation to fit the characteristics as derived by Rother et al. for the CHAMP PLP, the fitted electron temperature is found to be significantly lower when the magnetic field is oriented so as to magnetically connect both the probe and a physical object. This in turn is consistent qualitatively with the reported asymmetry in the electron temperature inferred from CHAMP’s PLP between the northbound and southbound legs of the orbit at midlatitudes [1] .

Effect of magnetic field orientation and disorder on Majorana polarization in wires with topological superconductivity

Majorana polarization, previously introduced by Sticlet et al. [Phys. Rev. Lett. 108, 096802 (2012)], is studied for wires in a topological superconductive state with varying orientation of the magnetic field. Numerical calculations show that in the case of a canted field, this polarization can differ in sign, as well as absolute magnitude, at the opposite ends of a wire. Since the Majorana polarization changes sign at one end when the orientation of the magnetic field is changed from perpendicular to longitudinal, there is always a range of angles for which this quantity is significantly suppressed or equals zero. Thus, the Majorana polarization does not always appear as a local order parameter for an arbitrary angle of the magnetic field in the plane perpendicular to the effective Rashba spin-orbital interaction field. It is shown that the introduction of disorder does not lead to qualitatively new effects. At the same time, additional regions with weak Majorana polarization do show up in high magnetic ...

Magnetic stabilization of fluidized beds: Effect of magnetic field orientation

Fluidized beds of granular materials can be stabilized by interparticle attractive forces which confer the expanded bed an elastic modulus that stabilizes it against flow perturbations. Stabilization in a structure of enduring contacts is seen to occur naturally due to the universal van der Waals forces for ∼50μm particle size beds albeit in a quite reduced interval of gas velocities over the minimum fluidization velocity vmf. As shown in this work, a magnetic field may induce attractive forces between magnetizable particles thus extending the stable fluidization interval well beyond vmf. The structure of the magnetically stabilized bed is however markedly anisotropic since attractive magnetic forces are maximum along the direction of the externally imposed field which leads to the formation of chain particle aggregates. This paper shows experimental measurements on the magnetic yield stress, gas velocity at the transition to marginal stability and microstructure of magnetostabilized beds as affected by the direction of the magnetic field. Data shows that magnetic stabilization is optimized for co-flow fields as chain aggregates are preferentially orientated parallel to the magnetic field and along the direction of minimum drag. As the magnetic field is tilted, particle chains become tilted according to a balance between the magnetic attractive force between the particles and the vertical drag force, which reduces the magnetic yield stress and therefore shortens the interval of magnetic stabilization.

Binary neutron star mergers and short gamma-ray bursts: Effects of magnetic field orientation, equation of state, and mass ratio

We present fully GRMHD simulations of the merger of binary neutron star (BNS) systems. We consider BNSs producing a hypermassive neutron star (HMNS) that collapses to a spinning black hole (BH) surrounded by a magnetized accretion disk in a few tens of ms. We investigate whether such systems may launch relativistic jets and power short gamma-ray bursts. We study the effects of different equations of state (EOSs), different mass ratios, and different magnetic field orientations. For all cases, we present a detailed investigation of the matter dynamics and of the magnetic field evolution, with particular attention to its global structure and possible emission of relativistic jets. The main result of this work is that we found the formation of an organized magnetic field structure. This happens independently of EOS, mass ratio, and initial magnetic field orientation. We also show that those models that produce a longer-lived HMNS lead to a stronger magnetic field before collapse to BH. Such larger fields make it possible, for at least one of our models, to resolve the MRI and hence further amplify the magnetic field. However, by the end of our simulations, we do not observe a magnetically dominated funnel and hence neither a relativistic outflow. With respect to the recent simulations of Ruiz et al 2016, we evolve models with lower and more realistic initial magnetic field strengths and, because of computational reasons, we do not evolve the accretion disk for the long timescales that seem to be required in order to see a relativistic outflow. Since all our models produce a similar ordered magnetic field structure, we expect that the results found in Ruiz et al 2016, where they only considered an equal-mass system with an ideal fluid EOS, should be general and, at least from a qualitative point of view, independent from mass-ratio, magnetic field orientation, and EOS.

Magnetic field-enhanced catalytic CO2 hydrogenation and selective conversion to light hydrocarbons over Fe/MCM-41 catalysts

Based on green and efficient utilization concepts, an external magnetic field is applied with an attempt to improve the catalytic performance in CO2 hydrogenation reaction. In this research, effects of magnetic field orientation and magnetic flux density on activity and selectivity of xFe/MCM-41 catalysts with ferro/ferrimagnetic property were investigated. With external magnetic field, especially in north-to-south (N-S) direction, CO2 conversions were significantly improved by 1.5–1.8 times; meanwhile, the activation energy was decreased by 1.12–1.15 times, compared to those of without magnetic field. Upon changing the magnetic flux density, CO2 conversion increased with increasing the magnetic flux density followed the order of 27.7mT>25.1mT>20.8mT. Furthermore, higher selectivities to C2-C3 hydrocarbons (2.5–5.3 times), and CH3OH (1.6 times) were observed at 180–200°C and 220°C, respectively. Among all the conditions with magnetic field, the highest CO2 conversion and selectivity to CH3OH and C2-C3 hydrocarbons were obtained at −27.7mT in N-S direction. These outstanding catalytic activities could be attributed to the fact that magnetic field help facilitate the reactant adsorption and surface reaction over the magnetized Fe catalysts, leading to the decrease of apparent activation energy, and also the increase of selectivities to hydrocarbons and CH3OH.

An experimental study on the effect of magnetic field orientations and electrolyte concentrations on ECDM milling performance of glass

In this work, effects of magnetic field orientation, machining voltage and electrolyte concentration on electrochemical discharge machining (ECDM) performance have been studied. The microchannels have been machined on the glass substrate; microchannel's depth and surface quality have been taken as indexes of machining characteristic. Experimental results show that the Lorenz force of magnetic field affects a direction of bubble's motion, consequently, changes the electrochemical discharge behavior of electrolyte. The presence of magnetic field causes magnetohydrodynamic (MHD) convection which, by its turn, accelerates the repulsion of the bubbles from the cathodic surface. However, it should mention that the direction of bubble movement depends on the magnetic field orientation. If the magnetic field orientation induces upward Lorenz force (downward Lorenz force), the gas bubbles will repel from (will attract to) inter-electrode area. The obtained results demonstrate that when the magnetic field applies, the machined surface will be smoother for the lower concentration values of electrolyte and higher machining voltages. Enhancements of both the machining voltage and electrolyte concentration increase the machining depth. For the same values of applied voltages, application of magnetic field will also increase the machining depth in a certain machining process duration; this will be intensified for the lower values of electrolyte concentration. The results of this study explain how the combination of the magnetic field orientation and the values of machining voltage and electrolyte concentration should be defined in order to increase both the channel depth and surface quality.

Numerical investigation of magnetic field inclination angle on transient natural convection in an enclosure filled with nanofluid

Purpose – The objective of present research is to characterize the unsteady thermal behavior of a square enclosure filled with water-Al2O3 nanofluids in the presence of oriented magnetic fields. The purpose this paper is to study the effect of pertinent parameters on the transient natural convection in the enclosure. Design/methodology/approach – In this research, an in-house implicit finite volume code based on the SIMPLE algorithm is utilized for numerical calculations. To ensure the accuracy of results, comparisons are also made with previous works in literature. In this study, a constant strength magnetic field is concerned and for Rayleigh numbers of Ra=103, 104 and 105 the effect of magnetic field orientation with respect to the case of zero inclination on the thermal performance of cavity is investigated at Hartmann number range of Ha=15-90. In the present work, the nano-particle volume fractions range from φ=0-0.06. Findings – Results show that when Rayleigh number is Ra=103, the inclination angle, solid particles and Hartmann number has no effect on the transient behavior. It is shown that during the time advancement to steady condition, the heat transfer rate relative to zero inclination angle, may reach to a maximum value. This relative maximum heat transfer increases as the inclination angle increases and decreases as the solid volume fraction increases. The effect of increase in Hartmann number is to decrease this maximum value at Rayleigh number of Ra=104 and at Rayleigh number of Ra=105, depending on the Hartmann number, this value may increase or decrease. It is also found that an increase in Hartmann number leads to delay the appearance of the relative maximum value of heat transfer. Results show that this maximum value is of more significance at zero solid volume fraction when inclination angle is 90 degrees and Hartmann number is Ha=60. Originality/value – Limited works could be found in the literature regarding the idea of using nanofluids as the working fluid in an enclosure in the presence of magnetic field. In these works, the steady state thermal behavior of enclosures subjected to fixed magnetic fields is concerned. In the present work, the unsteady thermal behavior is concerned and the effect of magnetic field orientation angles on transient heat transfer performance of the enclosure at different Rayleigh and Hartmann numbers and solid volume fractions is explored.

Liquid crystalline epoxy resin based on biphenyl mesogen: Effect of magnetic field orientation during cure

A biphenyl based epoxy monomer, 4,4′-diglycidyloxybiphenyl (BP), was synthesized and cured with a tetra-functional amine, sulfanilamide (SAA), to obtain a liquid crystalline epoxy network. The curing behavior of BP with SAA was studied using differential scanning calorimetry, polarized optical microscopy, and parallel plate rheology. Macroscopic orientation of the liquid crystalline epoxy resins (LCERs) was achieved by curing in a high strength magnetic field, and quantified by an orientation parameter determined with wide angle X-ray diffraction. The effects of orientation on the glass transition temperature, coefficient of thermal expansion, and dynamic mechanical properties of the LCERs were investigated. The results reveal that the formation of the liquid crystalline phase has a dramatic influence on the curing reaction, leading to a decrease in viscosity of the reacting system. Oriented LCERs exhibit anisotropic thermal expansion behavior and significant improvements of thermomechanical properties.

Effect of magnetic field orientation on fluidized beds of magnetic particles: Theory and experiment

Geldart-A fluidized beds of fine particles experience a jamming transition between a fluid-like state and a solid-like state at a certain superficial gas velocity, that depends on the relative strength of interparticle attractive forces with respect to particle weight. Interparticle forces provide the bed with a certain tensile strength in the jammed state. In the work presented here we analyze the behavior of a fluidized bed of magnetic particles subjected to an externally applied magnetic field, which contributes to enhance interparticle forces. The importance of the magnetic contribution to interparticle forces is measured by the changes in the tensile strength and the superficial gas velocity at the jamming transition. The link of the field orientation with the microstructure of the bed is discussed.