Effect Of Vertical Magnetic Field Research Articles

Effects of vertical magnetic field on natural convection of magnetic nanoscale fluid in a sinusoidal curved cavity partially filled with porous medium

In order to enhance heat dissipation effect of electronic components, this paper studied the cooling performance of a sinusoidal bending cavity partially filled with porous media under a vertical magnetic field, the main variables included nanofluids concentration (wt%=0.0, 0.1, 0.3, 0.5 %), magnetic strength (B=0.0, 0.01, 0.02, 0.03, 0.04 T), power (Q=10, 15, 20, 25 W), magnetic space layout (single-sided vertical, double sides vertical corresponding, bilateral vertical staggered), conclusion is that the double side vertical staggered magnetic field possesses better heat transfer, compared with deionized water, the Nu can be increased by 9.04 % at most under the double side vertical magnetic field, which provides some guidance for the heat transfer by convection in the heat exchange model of electronic equipment filled with some pore structure under the interference of external magnetic field.

Regulation of nanosecond pulse breakdown process by vertical magnetic field

Effects of vertical magnetic field on the breakdown process of the nanosecond pulse discharge in atmospheric air are studied via two-dimensional particle-in-cell/Monte Carlo collision simulations. The numerical model is chosen and defined reasonably, with reference to experimental situations and literature reports. It is shown that when the applied magnetic field is strong enough, the evolutionary characteristics of the ionization channel are greatly affected due to the Lorentz force on charged particles. The impact is manifested macroscopically by the slowing down of the ionization channel evolution speed, the ionization channel shift, and the improvement of the discharge uniformity. At the microscopic level, the impact is mainly reflected in the regulation of the highest-energy electrons and the regulation of the overall electron energy distribution. That is, the adoption of a strong vertical magnetic field is capable of suppressing the generation of energetic electrons. The authors' results explicitly demonstrate the regulation of vertical magnetic field on the breakdown process of the nanosecond pulse discharge, which provides more comprehensive knowledge for the atmospheric air gap nanosecond pulse discharge physics and the theoretical basis for application design.

Effect of Vertical Magnetic Field on the Electronic and Transport Properties of Armchair Silicene Nanoribbons

Effect of Vertical Magnetic Field on the Electronic and Transport Properties of Armchair Silicene Nanoribbons

An Analytical Study of Thermal Instability in a Nanofluid Layer with a Vertical Magnetic Field

The paper re-examines analytically the work of Yadav et al. ([43], [44]) (referred to as Y hereafter) wherein they have examined the combined effect of vertical magnetic field and the free-free, rigid-rigid and rigid-free boundaries on the onset of convection in an electrically conducting nanofluid layer heated from below. The key feature of the present paper is that it explains that the case M=0 ([43], [44]) is not justified either on physical or on mathematical grounds. Moreover, a number of sufficient conditions regarding the non-existence of oscillatory convection have been found.

Global Well-Posedness for the Three-Dimensional Full Compressible Viscous Non-resistive MHD System

In this paper, we consider the three-dimensional full compressible viscous non-resistive MHD system. Global well-posedness is proved for an initial-boundary value problem around a strong background magnetic field. It is also shown that the unique solution converges to the steady state at an almost exponential rate as time tends to infinity. The proof is based on the celebrated two-tier energy method, due to Guo and Tice [\emph{Arch. Ration. Mech. Anal.}, 207 (2013), pp. 459--531; \emph{Anal. PDE.}, 6 (2013), pp. 287--369], reformulated in Lagrangian coordinates. The obtained result may be viewed as an extension of Tan and Wang [\emph{SIAM J. Math. Anal.}, 50 (2018), pp. 1432--1470] to the context of heat-conductive fluids. This in particular verifies the stabilization effects of vertical magnetic field in the full compressible non-resistive fluids.

Numerical Modeling of Thermal and Flow Field in Directional Solidification Silicon under Vertical Magnetic Field

One of the key issues in the directional solidification (DS) process of multi-crystalline silicon (mc-Si) is to control the melt flow in order to achieve a higher quality of silicon ingot. A steady global model is developed to investigate the effects of vertical magnetic field (VMF) variation in industrial G5 DS furnace. The Solid/Liquid (S/L) interface, thermal and flow field during directional solidification of mc-Si have been simulated. The results show that, with B0 increases, the deflection of S/L interface decreases and melt flow rate is greatly inhibited. Through the analysis of the flow structure, it is found that two small vortexes in melt without B0 become a large vortex as B0 increases. The melt flow distribution is more uniform which is beneficial to obtain a homogeneous distribution of impurities. These results show the VMF can be adjusted to successfully obtain a more uniform flow distribution and a flatter S/L interface shape.

Grain refinement and orientation alternation of 10 mm 316L welds prepared by magnetic field assisted narrow gap laser-MIG hybrid welding

The effect of vertical magnetic field on grain size and orientation of ferrite (δ) and austenite (γ) in welds of 10 mm 316L stainless steel were investigated during multilayer narrow gap laser-MIG hybrid welding. Results show that shapes of weld beads are changed by the ampere force from “T” to “V” and “▪”, which results from arc current and magnetic field. The optimized fusion boundary accelerates thermal diffusion and raises temperature gradient, which reduces duration of high temperature of δ-γ solid phase transition and heat affected zone (HAZ). As a result, δ-islands and reduction of HAZ are observed. At the meantime, the growth direction of γ grains are altered from preferred 〈100〉-crystal direction to maximum temperature gradient with the increase of temperature gradient. Moreover, vermicular, continuous and reticular δ dendrites are changed to be skeletal, deflected and seaweed-like in the interface and columnar zone under the effect of magnetic field. The occurrence of this phenomenon is associated with the joint effect of ampere force, viscous resistance and hot metal liquid. And the fragment of primary δ dendrites leads to the refinement of γ grains and increase of central zone.

Effects of vertical magnetic field on impact dynamics of ferrofluid droplet onto a rigid substrate

The impact dynamics of a ferrofluid droplet on a tempered glass surface in the presence of a vertical magnetic field has been investigated experimentally. The results show how precise control of the impact dynamics of a ferrofluid droplet can be obtained.

Effect of Vertical Magnetic Field on the Flow and Heat Transfer Characteristics of Conducting Gas in a Cylinder

Effect of Vertical Magnetic Field on the Flow and Heat Transfer Characteristics of Conducting Gas in a Cylinder

Effect of Vertical Magnetic Field on the Onset of Double Diffusive Convection in a Horizontal Porous Layer with Concentration Based Internal Heat Source

Effect of Vertical Magnetic Field on the Onset of Double Diffusive Convection in a Horizontal Porous Layer with Concentration Based Internal Heat Source

Magneto-convection of a binary micropolar fluid with suspended particles

The present paper investigates the effect of vertical magnetic field and dust particles on the stability of a micropolar fluid layer heated and soluted from below. The Lorentz force term is introdu...

Rayleigh-Bénard Convection of Nanofluids with Magnetic Field and Permeability Effects

Effect of vertical magnetic field on thermal convection of a porous nanofluid layer is considered using Darcy's law. System of nanofluid layer in which nanoparticle concentration on the top is higher than that at the bottom is considered. Normal mode technique and single term Galerkin method is employed to investigate the stability and derive the eigen value problem. Brownian motion and thermophoretic forces are introduced due to the presence of nanoparticles. The mode of instability is invariably through stationary convection. The oscillatory instability may be possible when nanoparticles concentrate near the bottom of the layer, so that two buoyancy forces act in opposite directions. The value of the critical Rayleigh number is decreased by a substantial amount due to the presence of nanoparticles. The critical Rayleigh numbers and the critical wave numbers for alumina-water nanofluid and copper-water nanofluid for different values of Chandrasekhar number and porosityare found. Alumina-water nanofluid is found to exhibit higher stability as compared to copper-water nanofluid in the presence/absence of magnetic field and/or porous medium. Effect of nanoparticle volume fraction and temperature difference on stability of the system is investigated taking permissible values of various parameters. Magnetic field, Brownian to thermal diffusivity ratio and temperature difference is found to stabilize the nanofluid layer, appreciably, whereas the effect of volume fraction of nanoparticles, density ratio and porosity is to destabilize the layer.

Effect of Vertical Magnetic Field on the Chemical Wave Propagation Speed in Belousov–Zhabotinsky Reaction

Abstract Effects of a vertical magnetic field (maximum field, 4 T and 93 T2 m−1) on chemical wave front propagation from the Belousov–Zhabotinsky reaction were studied. Applied magnetic fields strongly affected the downward propagation speed in a glass tube. The magnetic force acting on the inhomogeneous solution explains the results.

In Situ Observation of Laser-Induced Convection of Water in High Magnetic Fields Using a Photochromic Reaction

Abstract The effects of vertical magnetic fields on laser-induced convection of water were studied using a photochromic reaction of a water-soluble 1,2-diarylethene (WSD). A thin blue disk of its photoisomer (PI) solution was formed on the bottom surface; it moved upward when the WSD aqueous solution was irradiated using a 355 nm laser from the bottom of the vessel. The lift speeds of the PI solution were about 2.5 (11 T, +1200 T2 m−1), 1.2 (11 T, −1500 T2 m−1), and 1.6 mm min−1 (15 T, −100 T2 m−1). All results are described in terms of the magnetic force acting on the PI solution.

In situ observation of the solution convection induced by magnetic force using photoreaction

The effects of vertical magnetic fields ( ⩽ 1260 T 2 / m ) on the laser-induced convection of a benzene solution were studied by using a photo-induced coloration reaction of CBr 4 and diphenylamine. A green solution, photo-generated at the bottom surface of a vessel, flowed against the magnetic field center. The speed of the solution depended strongly on the intensity and direction of the magnetic force. These effects were discussed in terms of the difference in the magnetic susceptibilities of the green solution and the surrounding one.

The Effects of Vertical Magnetic Fields on Segregation in HgCdTe

The Effects of Vertical Magnetic Fields on Segregation in HgCdTe

The Effect of a Vertical Magnetic Field on the Periods of Trapped g-modes in White Dwarfs

AbstractA white dwarf model with cylindrical symmetry is used to investigate the effect of a uniform vertical magnetic field on the periods of g-modes trapped in the compositionally stratified surface layers. For those modes for which trapping is most effective, the periods wander by approximately 10% about their zero-field values as B0 increases. As the field strength increases further, the period may abruptly increase by some 25% to a new, more stable value; see Figure 1. The periods of less efficiently trapped modes do not show this sensitivity for field strengths up to 1 MG, the upper limit examined.

Quantitative analysis of the effects of vertical magnetic fields on microsegregation in Te-doped LEC GaAs

Using near-IR transmission microscopy with computational absorption analysis, the effects of axial magnetic fields on micro- and macrosegregation during LP-LEC growth of GaAs were quantitatively investigated with a spatial resolution approaching 2 microns. Segregation inhomogeneities exceeding one order of magnitude are found to be related to fluid dynamics of the melt. The applicability of the BPS theory as well as the nonapplicability of the Cochran analysis are established.

Effect of vertical magnetic field on convection and segregation in vertical Bridgman crystal growth

The finite-element analysis of vertical Bridgman growth for dilute and non-dilute alloys presented before (J. Crystal Growth 80 (1987) 155) is extended to include the effect of a vertically-aligned magnetic field in the limit of zero magnetic Reynolds number. Calculations are presented for growth of a dilute gallium-germanium alloy in a vertically stabilized Bridgman-Stockbarger system and in a furnace with a uniform temperature gradient imposed along the ampoule. Steady cellular convection driven by radial temperature gradients causes good axial and radial mixing in both systems without a magnetic field. A weak magnetic field decreases the intensity of convection and the effectiveness of solute mixing. The radial non-uniformity is greatest for an intermediate field strength. Stronger fields suppress flow recirculation completely and lead to uniform solute segregation across the crystal and to diffusion-controlled axial segregation.

Effect of suspended particles on the thermal convection instability in hydromagnetics

The effect of suspended particles in a finitely conducting gas on the thermal convection instability is studied. The critical Rayleigh number at which instability sets in is reduced by the presence of suspended particles. The effect of vertical magnetic field is stabilizing. We also study the effect of conducting particles suspended in a non-conducting gas. It is found that the stabilizing effect of the magnetic field is reduced by the electrically conducting suspended particles.