Influence Of Non-uniform Magnetic Field Research Articles

Effect of non-uniform magnetic field on combustion products of aluminum nanopowder in mixture with titanium and zirconium dioxides

The morphology and phase composition of the combustion products in air of Al nanopowder mixed with diamagnetic TiO2 and ZrO2 was studied. The influence of non-uniform magnetic field on the combustion process of the oxide-metal powdery mixtures led to the stabilization of TiN and ZrN in the final products. The two-level whiskers of AlN formed at the combustion of Al-TiO2 mixture, while the agglomerated structures covering the large particles of ZrN formed at the combustion of Al-ZrO2 mixture. During combustion of oxide-metal mixtures in non-uniform magnetic field, diamagnetic metal dioxides are reduced to metals or their suboxides and then interact with atmospheric nitrogen.

Influence of non-uniform magnetic field on spatial orientation of Heisenberg dimers with spin [formula omitted

The paper presents exact results for the Heisenberg dimer with spin S=1 placed in a non-uniform magnetic field. It was assumed that the dimer has a degree of freedom of movement enabling the spatial arrangement of the dimer axis parallel or perpendicular to the field gradient. Based on the calculations of the Gibbs magnetic energy, the occurrence of magneto-spatial phase transitions of the 1st kind was found, in which the dimer changing its magnetization state simultaneously changes the spatial orientation relative to the field gradient. Ground state phase diagrams and temperature diagrams are presented, as well as calculations of the Gibbs energy, magnetization, entropy and dimer quadrupolar moment. These calculations form an internally consistent thermodynamic description and are presented in figures. The discussed model illustrates the possibility of a magnetic contribution to the self-assembly of dimers on the surface.

Influence of non-uniform magnetic field on the thermal efficiency hydrodynamic characteristics of nanofluid in double pipe heat exchanger

Enhancement of the heat transfer rate inside the double pipe heat exchangers is significant for industrial applications. In present work, the usage of non-uniform magnetic field on the heat transfer rate of the nanofluid flow streamed inside double pipe heat exchangers are comprehensively studied. Computational technique of CFD is used for the visualization of the nanofluid hydrodynamic in existence of the magnetic source. Influences of the magnetic intensity and nanofluid velocity on the heat transfer are also presented. Simple algorithm is used for the modeling of the incompressible nanofluid flow with addition of magnetic source. Presented results show that magnetic source intensifies the formation of the circulation in the gap of the inner tube and consequently, heat transfer is enhanced in our domain. Comparison of different geometries of tube reveals that the triangle tube is more efficient for improvement of the heat transfer of nanofluid flow. Our results indicate that heat transfer in the tube with triangular shape is more than other configurations and its performance is 15% more than smooth tube.

Thermal performance of Fe3O4/water nanofluid flow in a newly designed dimpled tube under the influence of non-uniform magnetic field

The effects of alternating and constant magnetic fields on heat transfer characteristics of nanofluid flow in a dimpled tube have not been investigated either numerically or experimentally. In this context, the hydrothermal performance of Fe3O4/water (1.0 vol%) ferronanofluid flow in the dimpled tube (P/d = 3.75 and 11.25) has been examined under laminar flow regime (1131 ≤ Re≤2102) in this experimental study. While the magnitudes of magnetic fields are 0.16 T, the alternating magnetic field is utilized with square wave type at frequencies of 1, 2, 5 Hz. It is concluded that the dimpled tube causes up to 78.4% increase in Nusselt number compared to the smooth tube, while up to 118.9% increase in Darcy friction factor. The constant magnetic field enhances the Nusselt number up to 4.04% compared to the absence of a magnetic field using ferronanofluid as a working fluid. Higher frequencies of the alternating magnetic field results in higher thermal performance. Alternating magnetic field effect with f = 5 Hz offers 37.3% Nusselt number enhancement compared to the constant magnetic field effect in all tube geometries. It was also seen that P/d = 11.25 gives the highest Performance Evaluation Criteria while the magnetic field effect decreases it in all tube geometries.

Thermal Performance of Fe3o4/Water Nanofluid Flow in a Newly Designed Dimpled Tube Under the Influence of Non-Uniform Magnetic Field

Thermal Performance of Fe3o4/Water Nanofluid Flow in a Newly Designed Dimpled Tube Under the Influence of Non-Uniform Magnetic Field

Influence of non-uniform magnetic field on magnetic susceptibility, heat capacity, electronic and optical properties of a charged particle

Influence of non-uniform magnetic field on magnetic susceptibility, heat capacity, electronic and optical properties of a charged particle

Magnetic bubbles dynamics and heat transfer characteristics under influence of non-uniform magnetic fields

The computational study of transient immiscible and incompressible two-phase flows is one of the most common and desirable way for investigation of engineering phenomena and physics science. In the previous studies, generally bubbles current have been used as an active method for increasing heat transfer, however, due to existence of hydraulic boundary layers, the bubbles were not able to cross over this layer to thinning the thermal boundary layer and consequently the efficiency of this method was not very considerable. In this study, by considering potential of magnetic field, the effect of co-applying of external non uniform magnetic field and magnetic bubbles in enhancing the heat transfer efficiency in a 3-D tube has been investigated. The computational model consisted of the Navier–Stokes equation for liquid phase and VOF model for interface tracking are carried out by OpenFOAM. The external magnetic field has been considered non-uniform and time dependent. The results predicted that magnetic bubbles and external magnetic field due to their effect on thermal boundary layer increased significantly heat transfer and Nusselt number. Furthermore, results indicated magnetic bubbles can act as an active torbulators in the flow field and can be applied for increasing recirculation and secondary flow in the flow field. The average temperature and magnetic field over times for different cases have been discussed in the results.

A quantum hydrodynamical model of skyrmions with electrical dipole moments and novel magneto-electric skyrmion Hall effect

Abstract To introduce novel ways of manipulating the skyrmion dynamics we need to develop new fundamental models. Many-particle quantum hydrodynamics allows us to study inter-skyrmion interactions in the approximation of point-particle skyrmions, which were discovered in multiferroic insulators, where the spiral magnetic structure is accompanied by a finite electric dipole moment. We propose a new model of many-particle quantum hydrodynamics for dipolar skyrmions with dipole–dipole interaction, in the presence of electric and magnetic field gradients. Based on the developed model we find a new way to control the positions of skyrmions, using the crossed gradients of magnetic and electric fields or a novel magneto-electric Hall effect. We have shown that the influence of non-uniform magnetic field provides circular motion of the dipolar skyrmion in the plane with the frequency determined by the derivative of the external magnetic field and the amplitude of the dipole moment. We study the wave processes in the system of skyrmions. We investigate hydrodynamic waves in a skyrmion gas in crossed non-uniform electric and magnetic fields, and predict the generation of a new type of hydrodynamic waves and instabilities. Also, we predict a new type of polarization waves in a rigid skyrmion gas with the dipole–dipole interaction.

Influence of Nonuniform Magnetic Field on the Helicon Discharge Excited by Various Antennas

The influence of a nonuniform magnetic field, which increases with the distance from an inductive antenna, on a helicon discharge has been studied. The discharge was excited in the azimuthally symmetric mode of helicon waves, m = 0, making use of antennas of two different types. It is shown that if the discharge is produced by a loop antenna, which supplies the RF energy through the side boundary of plasma and perpendicularly to the external magnetic field, then the ionization is concentrated at the discharge periphery. Under those conditions, the imposing of a nonuniform magnetic field reduces the loss of ionizing electrons at the wall and enhances the plasma generation. If the discharge is excited with a planar antenna along the magnetic field, then the main ionization occurs in the inner plasma region around the axis. In this case, an increase in the plasma density, if any, may be a result of the plasma contraction in the magnetic field with force lines convergent to the axis.

An unsteady flow of magnetic nanoparticles as drug carrier suspended in micropolar fluid through a porous tapered arterial stenosis under non-uniform magnetic field and periodic body acceleration

A mathematical model has been developed for pulsatile flow of blood through a tapered arterial stenosis in a porous medium under the influence of non-uniform magnetic field and periodic body acceleration treating blood as micropolar fluid carrying iron oxide nanoparticles. The governing equations of the system are solved numerically using finite difference schemes. The effects of stenotic height, taper angle, micropolar parameters, magnetic field, porosity, pulsatility, and magnetic nanoparticles on the flow of blood are analysed, and the results are represented graphically. It is significant to note that the flow parameters such as wall shear stress and flow resistance increase with increase in stenotic height, tapering parameter, magnetic field, pulsatile Reynolds number, time period, particle concentration, and particle mass parameters. Wall shear stress decreases with the increasing values of coupling number and it shows opposite behaviour in the case of flow resistance. Also increase in Darcy number leads to decrease in wall shear stress and flow resistance. The significance of treating blood as micropolar fluid is that the rotation of particles is taken into account. Cardiovascular diseases occur mainly due to abnormal blood flow in the arteries. To normalize the blood flow in the arteries, analysis of parameters involved in the study is essential. Hence, the present study has various applications in biomedical sciences. The effects of nanoparticles on blood flow analysed in the study have significant applications in delivery of drugs for treating cancer.

The influence of non-uniform magnetic field on heat transfer intensification of ferrofluid inside a T-junction

In this research, the effects of non-uniform magnetic field on the heat transfer of ferrofluid inside a T-junction are investigated. The finite volume method with the SIMPLEC algorithm is applied to simulate the effects of non-uniform magnetic field on the thermal and friction factor of ferrofluid. The ferrofluid inside T-junction is assumed single phase and laminar and constant heat flux is applied on the wall while three wires are chosen as a source of non-uniform magnetic field. This study focused on main effects of magnetic field on the flow feature and temperature distribution in the vicinity of magnetic source. Comprehensive parametric studies are performed to investigate the influence of various factors such as intensity of magnetic field and Reynolds number on the heat transfer. Obtained results show that average heat transfer of ferrofluid rises more than 64% when magnetic field is applied. In addition, the local heat transfer increases more than 200% in vicinity of the first magnetic field.

Heat transfer of Fe3O4–water nanofluid in a permeable medium with thermal radiation in existence of constant heat flux

Influence of non-uniform magnetic field on Fe3O4–water ferrofluid flow in a porous cavity is simulated. Shape factor effect on nanofluid properties is taken into consideration. Vorticity stream function formulation is reported. The solutions of final equations are obtained using CVFEM. Figures are depicted for different values of radiation parameter (Rd), Darcy number (Da), Fe3O4–water volume fraction (ϕ), Rayleigh (Ra) and Hartmann (Ha) numbers. Results show that augmenting in Hartmann number leads to decrease in velocity of nanofluid and heat transfer rate. Utilizing Platelet shaped nanoparticles results the highest Nusselt number.

Numerical investigation of non-uniform magnetic field effects on the blood velocity and magnetic nanoparticles concentration inside the vessel

Among other applications, Magnetic nanoparticles (MNPs) are used as drug carriers for guided drug delivery purposes. The aim of the current study is to numerically investigate the effect of non-uniform magnetic field on the blood flow and MNPs concentration inside a vessel. The coupled governing equations under the influence of non-uniform magnetic field are utilized and non-dimensionalized. Two dimensionless parameters, Magnetic force number (MFN) and Magnetic drift number (MDN), are introduced and their effects on the blood flow velocity and the MNPs concentration are studied. The results show for the same magnetic force number, the MNPs concentration on the vessel wall increases as the magnetic drift number increases. While under the same magnetic drift number, magnetic nanoparticles decreases as magnetic force number increases. This implies that the MNPs concentration at the entrance is low while MNPs radius is large. In addition, the greater the magnetic force and the magnetic drift numbers is the higher the deformation of streamlines becomes.

함정에서 발생하는 자계신호의 성분분리에 대한 검토

This paper investigated the separation of magnetic signal from a ferro-magnetic object. The magnetic signals were ILM(induced longitudinal magnetization) and IVM(induced vertical magnetization), which were induced by earth magnetic field and PLM(permanent longitudinal magnetization) and PVM(permanent vertical magnetization), which were due to a permanent magnetization of the object, respectively. Magnetic signal separation was based on the fact that magnetization vector could be analyzed according to longitudinal and vertical directions. Also the influence of non-uniform magnetic field from a rectangular coil on the separation was examined. A military vessel with a size close to rectangular coil has more errors on the magnetic signal separation.

Liquid cooling enhancement by means of magnetic fields

The goal of this work is to provide a preliminary evaluation of a new high-potential concept for liquid cooling: an electrically conductive fluid can flow through channels, while magnetic fields promote flow-wall impinging, causing an effect analogous to channel ribs (turbulence promoters), but in principle the effect is controllable. In order to evaluate the magneto-hydrodynamic effect, DNS has been used to investigate the influence of non-uniform magnetic fields on liquid metal flowing through a two-dimensional channel. The dimensionless numbers governing this flow field are the Reynolds (Re) and the Stuart (St) numbers. The latter provides the relative weight of the Lorentz forces with respect to the inertial forces. A liquid-lithium flow in laminar regime has been simulated both in absence of the magnetic field (Re = 2000, St = 0) and for increasing values of the Stuart number (Re = 2000, St equal to 750, 1000 and 2000), with the aim of putting into evidence the effects of magnetic forces on the magnitude of convective heat transfer. For a channel with a hydraulic diameter of 2 cm, such Stuart number range corresponds to magnetic field intensities varying between 1 and 2T, which are technically feasible by using either electromagnets or permanent magnets. Simulation results show that the local Nusselt number can be up to 2.8 times higher than that evaluated in the non-magnetic case.

Separation of bubbles from solid surfaces in magnetic fluids

Experimental investigation of air bubbles separation in magnetic fluid from the solid surfaces with the presence of uniform and non-uniform magnetic fields is presented in this work. The critical volumes of the bubbles and the dependences on magnetic field are ascertained. The strong influence of non-uniform magnetic field on bubble separation from the solid plate is observed.

Ballistic Quantum Transport: Effect of Geometrical Phases

We study the influence of nonuniform magnetic fields on the magneto conductance of mesoscopic microstructures. We show that the coupling of the electron spin to the inhomogenous field gives rise to effects of the Berry phase on ballistic quantum transport and discuss adiabaticity conditions required to observe such effects. We present numerical results for different ring geometries showing a splitting of Aharonov-Bohm conductance peaks for single rings and corresponding signatures of the geometrical phase in weak localization. The latter features can be qualitatively explained in a semiclassical approach to quantum transport.

Influence of nonuniform magnetic fields on orientation of plant seedlings in microgravity conditions.

Experiments on the spatial behavior of the flax (Linum usitatissimum, L.) seedlings in a nonuniform magnetic field were conducted on the orbital space stations "Salut" and "Mir". This field can displace sensory organelles (statoliths) inside receptor cells and such displacement should cause a physiological reaction of the plant-tropistic curvature. Experiments were conducted in the custom-built "Magnetogravistat" facility, where seeds were germinated and grown for 3-4 days in a magnetic field with the dynamic factor grad (H2/2) approximately equal to 10(7) Oe2/cm, then fixed on orbit and returned to Earth for analysis. It was found, that 93% of the seedlings were oriented in the field consistently with curvature in response to displacement of statoliths along the field gradient by ponderomotive magnetic forces, while control seedlings grew in the direction of the initial orientation of the seed. This suggests, that gravity receptors of plants recognized magnetic forces on statoliths as gravity, and that gravity stimulus can be substituted for plants by a force of a different physical nature.

Influence of nonuniform magnetic field on a ferrite junction circulator

We have analytically formulated the problem that a ferrite circulator junction is biased by a nonuniform magnetic field. Interport impedances of the junction can, therefore, be solved numerically. Nonuniform-bias field will reduce the transmission bandwidth, and the circulation condition is apt to be altered if the bias field shows nonuniformity near the center of the junction. Our calculation compares very well with measurements.