Transverse Static Magnetic Field Research Articles

Numerical simulation of natural convection in a rectangular enclosure filled with porous medium saturated with magnetic nanofluid using Buongiorno's two‐component model

AbstractMotivated by studying emerging nanofluid‐based magnetic fuel cells and hybrid direct absorber solar collectors, a numerical study is presented for buoyancy‐driven flow in a vertical enclosure containing a porous medium saturated with magnetized nanofluid flow under a transverse static magnetic field. The enclosure features adiabatic side walls and vertical heat slits, ensuring consistent cold temperatures on the lower and upper bounded walls. The side walls of the regime are insulated, and the hot slits are centrally located on these walls. The finite difference method (FDM) is applied to employ the transformed dimensionless vorticity–stream function (VSF) formulation of the transport equations. The impact of pertinent parameters on isotherm, streamline, iso‐concentration, and average Nusselt and Sherwood numbers are visualized with contour plots and graphs. Increasing Darcy number values tend to amplify the isotherm magnitudes. Higher Hartmann (magnetic) number values, on the other hand, lead to a reduction in local Nusselt number profiles but do not significantly modify the local Sherwood number. The porous medium permeability, as simulated via the Darcy number, has a strong impact on streamlines, thermal contours, and iso‐concentrations. A reduction in Darcy's number suppresses local Nusselt and Sherwood numbers, whereas an elevation in Rayleigh's number enhances them. Increasing the Buongiorno nanoscale Brownian motion parameter enhances local Nusselt and Sherwood numbers at both cold walls of the enclosure. The simulations provide a deeper insight into enclosure flows involving electrically conducting nanofluids in advanced processing systems for nanomaterials and hybrid fuel cells utilizing electromagnetic and liquid fuel technologies.

Magnetic Field Sensing via Acoustic Sensing Fiber with Metglas® 2605SC Cladding Wires

Magnetic field sensing has the potential to become necessary as a critical tool for long-term subsurface geophysical monitoring. The success of distributed fiber optic sensing for geophysical characterization provides a template for the development of next generation downhole magnetic sensors. In this study, Sentek Instrument’s picoDAS is coupled with a multi-material single mode optical fiber with Metglas® 2605SC cladding wire inclusions for magnetic field detection. The response of acoustic sensing fibers with one and two Metglas® 2605SC cladding wires was evaluated upon exposure to lateral AC magnetic fields. An improved response was demonstrated for a sensing fiber with in-cladding wire following thermal magnetic annealing (~400 °C) under a constant static transverse magnetic field (~200 μT). A minimal detectable magnetic field of ~500 nT was confirmed for a sensing fiber with two 10 μm cladding wires. The successful demonstration of a magnetic field sensing fiber with Metglas® cladding wires fabricated via traditional draw processes sets the stage for distributed measurements and joint inversion as a compliment to distributed fiber optic acoustic sensors.

Computational analysis of magnetized Casson liquid stretching flow adjacent to a porous medium with Joule heating, stratification, multiple slip and chemical reaction aspects

This article aims to investigate the characteristics of thermo-solutal magnetohydrodynamic (MHD) non-Newtonian smart coating boundary layer flow of a stretching substrate adjacent to a porous medium, considering the influence of chemical reactions and thermal radiation subject to a transverse static magnetic field. A non-Darcy drag force model is deployed to capture both Darcy bulk drag and inertial Forchheimer (quadratic) drag effects. A diffusion flux model is deployed for radiative heat transfer. The Casson viscoplastic model has been utilized to simulate rheological characteristics. Due to polymeric slip effects, three slip phenomena are included at the wall (hydrodynamic, thermal and concentration) in the formulation. Furthermore, viscous dissipation and Ohmic heating (Joule dissipation) are also included. Robust scaling similarity variables are deployed to transform the governing partial differential equations into ordinary differential equations. Subsequently, the emerging dimensionless coupled nonlinear boundary value problem is solved utilizing the Bvp4c method in MATLAB version 2022. This numerical approach allows for a logical parametric examination of all key control parameters on the transport phenomena, enabling a comprehensive understanding of the system behavior. Validation with previous studies is included. Detailed graphical and tabular computations are included for velocity, temperature, concentration, skin friction, Nusselt number and Sherwood number, for the influence of Darcian parameter, Forchheimer inertial parameter, mixed convection, velocity (momentum) slip, magnetic number, Casson parameter, nonlinear thermal convection parameter, nonlinear concentration convection parameter, radiation parameter, thermal stratification parameter, Prandtl number, heat source/sink parameter, Eckert number, thermal slip parameter, Schmidt number, chemical reaction, solutal stratification parameter and solutal slip parameter. Detailed interpretation of the physics associated with these multiple effects is included. The simulations provide further insight into the transport characteristics of electromagnetic viscoplastic coating material manufacturing.

Morphology Refinement of Eutectic Carbides Assisted by Static Magnetic Field during Laboratory Electroslag Remelting Process

A transverse static magnetic field (TSMF) is implemented in a laboratory electroslag remelting (ESR) experiment to control eutectic carbides morphology of Cr8 die steel herein. Under action of a TSMF, the temperature distribution of the molten pool becomes homogeneous, the local solidification time is shortened, and the interdendritic region space shrinks, which result in an evenly spaced distribution of solute atoms and a reduction in interdendritic segregation. Therefore, the formation and subsequent growth of eutectic carbides are further inhibited, thereby causing the generation of smaller and more uniform distributed eutectic carbides due to the application of the TSMF. Moreover, the increase of the number of Al2O3–(Ti,V)N inclusions serves to be the heterogeneous nucleus of carbides (inclusions also become finer) caused by TSMF, which also contributes to the refinements of eutectic carbides in Cr8 ingots.

On the formation of gradient-distributed dendrites in a single crystal nickel-based superalloy directionally solidified under transverse static magnetic field

Directional solidification (DS) of alloys under static magnetic field has attracted extensive attention due to the development of thermoelectric magnetohydrodynamics (TEMHD). Assessing the influence of static magnetic field on solidification microstructures in single crystal (SX) superalloys is of great significance for both the development of SX superalloys and the understanding of external field-assisted solidification. In this contribution, under different transverse static magnetic fields, the evolution of dendritic structure in a SX nickel-based superalloy directionally solidified over a range of solidification velocities is systematically investigated. The results show that applying a transverse static magnetic field (TSMF) during DS does not disrupt the crystal orientation of SX superalloys. The distribution of dendrites or local primary dendrite arm spacings within the cross section of SX superalloys shows a gradient variation in the direction perpendicular to the TSMF. Additionally, the formation of gradient-distributed dendritic structure is closely related to the applied TSMF intensity and solidification velocity. It is easier to form a gradient-distributed dendritic microstructure at low solidification velocities and high magnetic fields. Based on the experiments and simulations, the formation of gradient-distributed dendritic microstructure is supposed to attribute to the variation of interdendritic constitutional undercooling created by the change of solute concentration in interdendritic region, which is induced by the TEMHD. The SX superalloy with a gradient distribution of dendrites may have potential applications due to its gradient properties. Meanwhile, these findings also provide a new method for preparing alloys with gradient microstructures.

Electromagnetohydrodynamic (EMHD) convective transport of a reactive dissipative carreau fluid with thermal ignition in a non-Darcian vertical duct

A mathematical model is developed to simulate the steady, laminar exothermic reactive electromagneto-hydrodynamic combustible non-Newtonian natural convective transport in a vertical duct. Static uniform axial electrical field and transverse magnetic field are imposed. The Frank-Kamenetskii thermal explosion theory is utilized and also the Carreau fluid model, the latter due to its ability to simulate shear-thinning, Newtonian and shear-thickening behaviour. The duct contains a homogenous, isotropic porous medium and to accomodate Forchheimer inertial drag effects, a non-Darcian model is deployed. The duct walls are permeable enabling suction and injection effects to be studied. Viscous and Joule heating (Ohmic dissipation) are also featured in the model. Following a scaling transformation, the dimensionless emerging non-linear ordinary differential boundary value problem is solved with a robust numerical method (Mathematica shooting algorithm). Validation with an Adomian decomposition method (ADM) is included.

Turbulent Lorentz heat flow visualization in radiative boundary layer regime

Modern nuclear energy systems often employ the magneto-hydrodynamic and feature radiative heat transfer. Motivated by studying the near-wall transport phenomena in such applications, the present article examines the simultaneous influence of thermal radiative flux and magneto-hydrodynamics on two-dimensional electrically conducting natural convective turbulent heat transfer about a vertical surface under a transverse static magnetic field using the low Reynolds number kinetic energy and dissipation (k – ε) model. An optimized Crank–Nicolson finite difference method is applied to solve the nonlinear and coupled system of Reynolds-averaged boundary layer equations. Numerical computations are conducted to visualize the streamlines and heatlines in laminar and turbulent regimes via mathematical stream and heat functions based on the Bejan approach. A detailed parametric study of the effects of the magnetic field, radiative flux, and turbulent Reynolds number on flow average velocity, temperature, kinetic energy, and dissipation rate is conducted. The simulations reveal that an increase in the magnetic field intensity reduces the average velocity and dissipation rate, whereas an increase in thermal radiation decreases the time mean temperature. The study also includes contour plots of turbulence energy and dissipation rate, along with skin friction coefficient and Nusselt number. The obtained numerical outcomes are compared to previous literature, and a good agreement is found.

Computation of stagnation coating flow of electro-conductive ternary Williamson hybrid mathrm{GO}-mathrm{AU}-{mathrm{Co}}_{3}{mathrm{O}}_{4}/mathrm{EO} nanofluid with a Cattaneo–Christov heat flux model and magnetic induction

Modern smart coating systems are increasingly exploiting functional materials which combine multiple features including rheology, electromagnetic properties and nanotechnological capabilities and provide a range of advantages in diverse operations including medical, energy and transport designs (aerospace, marine, automotive). The simulation of the industrial synthesis of these multi-faceted coatings (including stagnation flow deposition processes) requires advanced mathematical models which can address multiple effects simultaneously. Inspired by these requests, this study investigates the interconnected magnetohydrodynamic non-Newtonian movement and thermal transfer in the Hiemenz plane's stagnation flow. Additionally, it explores the application of a transverse static magnetic field to a ternary hybrid nanofluid coating through theoretical and numerical analysis. The base fluid (polymeric) considered is engine-oil (EO) doped with graphene left(GOright), gold left(Auright) and Cobalt oxide left(C{o}_{3}{O}_{4}right) nanoparticles. The model includes the integration of non-linear radiation, heat source, convective wall heating, and magnetic induction effects. For non-Newtonian characteristics, the Williamson model is utilized, while the Rosseland diffusion flux model is used for radiative transfer. Additionally, a non-Fourier Cattaneo–Christov heat flux model is utilized to include thermal relaxation effects. The governing partial differential conservation equations for mass, momentum, energy and magnetic induction are rendered into a system of coupled self-similar and non-linear ordinary differential equations (ODEs) with boundary restrictions using appropriate scaling transformations. The dimensionless boundary value problem that arises is solved using the bvp4c built-in function in MATLAB software, which employs the fourth-order Runge–Kutta (RK-4) method. An extensive examination is conducted to evaluate the impact of essential control parameters on the velocity f{^{prime}}left(zeta right), induced magnetic field stream function gradient g{^{prime}}left(zeta right) and temperature theta left(zeta right) is conducted. The relative performance of ternary, hybrid binary and unitary nanofluids for all transport characteristics is evaluated. The inclusion of verification of the MATLAB solutions with prior studies is incorporated. Fluid velocity is observed to be minimized for the ternary mathrm{GO}–mathrm{Au}–{mathrm{Co}}_{3}{mathrm{O}}_{4} nanofluid whereas the velocity is maximized for the unitary cobalt oxide left({mathrm{Co}}_{3}{mathrm{O}}_{4}right) nanofluid with increasing magnetic parameter (beta ). Temperatures are elevated with increment in thermal radiation parameter (Rd). Streamlines are strongly modified in local regions with greater viscoelasticity i.e. higher Weissenberg number (We). Dimensionless skin friction is significantly greater for the ternary hybrid GO–Au–C{o}_{3}{O}_{4}/EO nanofluid compared with binary hybrid or unitary nanofluid cases.

Solute segregation behavior of nickel-based single crystal superalloys directionally solidified under transverse static magnetic field

Solute segregation behavior of nickel-based single crystal superalloys directionally solidified under transverse static magnetic field

Cleanliness improvement and microstructure refinement of H13 die steel by laboratory magnetic-controlled electroslag remelting

The current work investigated the impact of transverse static magnetic field (TSMF) with varied magnetic flux density (MFD) on cleanliness and microstructure of laboratory scale electroslag remelted H13 die steel. The inclusion morphology and microstructure evolution of electroslag remelted ingots were examined utilizing scanning electron and optical microscopes, respectively. The number and size of inclusions in ingots were detected using the FEI Aspex Explorer. The results demonstrated that the number/size of inclusions in H13 electroslag remelted ingots were decreased as the MFD of applied TSMF increased. This resulted from the application of the TSMF, which produced the thinner liquid melting film (LMF), smaller droplets, and shallower metal molten pool, strengthening the kinetic conditions for inclusion migration to the slag-metal interface and the removal process. When the MFD of the applied TSMF was higher (95 mT and 140 mT), the LMF became thinner, the droplets became smaller, and the metal pool became shallower were more visible. Moreover, the metal pool became shallower and the local solidification time became shorter after applying TSMF with larger MFD, resulting in finer dendritic structure and carbides.

Three techniques for measuring the transverse relaxation time of cesium atoms

The transverse relaxation time (T2) is an important indicator to determine the fundamental sensitivity limit of alkali-metal atomic magnetometers. We propose a method based on the principle of longitudinal field modulation that obtains T2 by scanning the transverse static magnetic field. The previous technique of extracting T2 from the linewidth of the modulation frequency and the traditional magnetic-resonance-broadening-fitting method are also described. The T2 measurements of Cesium (Cs) atoms are carried out through these three methods, whose operating environments are applicable to different atomic magnetometers, respectively. The method that we propose can be used for obtaining the T2 of Cs atoms as well as detecting the transverse static magnetic field and is customized for the study of the Cs–Xenon ensemble for the construction of nuclear magnetic resonance gyroscopes. Moreover, the relationship between the limit sensitivities and cell temperatures is further studied in the experiment.

Refinement of Eutectic Carbides in M2 High Speed Steel by Adjusting Magnetic Flux Density During Magnetic Controlled ESR Process

The current study examines the effect of magnetic flux density (MFD) on the morphology of the metal pool and the refinement of eutectic carbides in magnetic controlled electroslag remelting (MC-ESR, M2 high speed steel). When a transverse static magnetic field (TSMF) with a larger MFD was used, it was easier to obtain a shallower metal pool and finer eutectic carbides. These phenomena are explained by the smashing effect of the droplet neck (stronger at higher MFD values) induced by electromagnetic vibration, resulting in smaller/more dispersed droplets and thus a more uniform temperature distribution in the metal pool. Additionally, as MFD increased, the local solidification time (LST) decreased (0 to 140 mT) and the number of inclusions serving as heterogeneous nuclei for eutectic carbide formation increased (0 to 65 mT), resulting in a gradual size reduction of eutectic carbides. However, the refinement of eutectic carbides in MC-ESR must consider the above two factors comprehensively, and the MFD of applied TSMF need not be excessively large.

Tailoring Microstructure and Microsegregation in a Directionally Solidified Ni-Based SX Superalloy by a Weak Transverse Static Magnetic Field

Tailoring Microstructure and Microsegregation in a Directionally Solidified Ni-Based SX Superalloy by a Weak Transverse Static Magnetic Field

Forming mechanism and tribological properties of a Ni-based coating prepared from transverse static magnetic field-assisted supersonic plasma spraying

Magnetic field-assisted forming represents an environmentally friendly, contactless and high-efficiency technology for the development of advanced in situ manufacturing. The application of this technology provides a new concept for improving the properties of ferromagnetic wear-resistant coatings. In this study, we combine magnetic field-assisted forming with supersonic plasma spraying to prepare a Ni-based coating assisted by a transverse static magnetic field. The porosity of the magnetic field-assisted coating is below 2%, the hardness of the coating increases from 638.46 to 785.45 MPa and the tribological coefficient decreases from 0.466 to 0.422. The presence of the static magnetic field directly affects the bubble movement during the forming process of the coating, which makes the bubbles escape outward and reduces the porosity of the coating. The presence of the static magnetic field also further improves the phase structure of the coating, so that the magnetic domain distribution is uniform and the hard phase inside the coating increases. Finally, the residual stress and tribological properties of the coating are also improved.

Solute Segregation Behavior of Nickel-Based Single Crystal Superalloys Directionally Solidified Under Transverse Static Magnetic Field

Solute Segregation Behavior of Nickel-Based Single Crystal Superalloys Directionally Solidified Under Transverse Static Magnetic Field

Morphology tailoring of metal pool and eutectic carbides in magnetic-controlled electroslag remelted M2 high-speed steel

A transverse static magnetic field (TSMF) was superimposed during electroslag remelting (ESR) process to regulate the shape of metal pool, the eutectic carbides morphology as well as the mechanical properties of electroslag remelted M2 high-speed steel (HSS) in current study. The metal pool became shallower and flatter after applying a 65 mT TSMF. Moreover, refined eutectic carbides and solidification structure (tended to grow axial) of the ESR ingot were obtained, together with uniform/improved mechanical properties (hardness, wear). Modifications of the morphology of metal pool and grain growth angle under the TSMF were attributed to a periodic electromagnetic excitation effect on droplets transition characteristics, which changed the drop path of the droplets (single to multiple drop) and homogenized the temperature distribution in metal pool. In addition, local solidification time (LST) became shorter and the number of inclusions ((Ti, V)N–Al2O3 and (Ti, V)N) which acted as heterogeneous nuclei for eutectic carbides formation increased (the inclusions also became finer) due to TSMF, resulting in the refinement of the eutectic carbides in ESR ingots.

Outside Front Cover: Plasma Process. Polym. 9/2021

Outside Front Cover: The nonlocal to local transition of discharge regime can be induced by applying a transverse static magnetic field oriented parallel to the electrodes in capacitively coupled plasmas (CCP) for various discharge frequencies. The discharge transition happens when the ratio of cyclotron frequency (fast electron ~ 30eV) and discharge frequency (fc/frf) is around 2.06. The discharge characteristics can thus be roughly predicted based on fc/frf in magnetized CCP. Further details can be found in the article by Yu-Qing Guo, Jing-Yu Sun, Quan-Zhi Zhang, Fang-Fang Ma, Xiang-Mei Liu, and You-Nian Wang (e2100072).

Morphology transition of eutectic carbide assisted by thermoelectric magnetic force during the directional solidification of M2 high-speed steel

ABSTRACT The morphology of eutectic carbide was studied by application of a transverse static magnetic field (TSMF) during the directional solidification of M2 high-speed steel. The results show that the morphology of eutectic carbide changed from lamella to fibre as the magnetic flux density (MFD) increased from 0 to 1 T. The transformation from lamella to fibre has been enhanced by the increasing MFD. Solute elements moved and gathered at a certain region in the mushy zone when imposing a TSMF. In the mushy zones, channel segregations were formed in the samples treated by 0.2 and 0.4 T TSMF. When the MFD increased to 0.8 and 1 T, the channel segregation disappeared. Morphology transition, solute elements movement and formation of channel segregation were attributed to the thermoelectric magnetic force (TEMF). This work provides a new method to control the distribution of carbides in steel assisted by TEMF.

Heat transfer enhancement with nanofluid in an open enclosure due to discrete heaters mounted on sidewalls and a heated inner block

Purpose The purpose of this study is to explore the heat transfer enhancement in copper–water nanofluid flowing in a diagonally vented rectangular enclosure with four discrete heaters mounted centrally on the sidewalls and a square-shaped embedded heated block in the influence of a static magnetic field. Design/methodology/approach Four discrete heaters are mounted centrally on each sidewall of the rectangular enclosure that embraces a heated square block. A static transverse magnetic field is acting on the vertical walls. The Navier–Stokes equations of motion and the energy equation are modified by incorporating Lorentz force and basic physical properties of nanofluid. The derived momentum and energy equations are tackled numerically using the successive over-relaxation technique associating with the Gauss–Seidel iteration technique. The effects of physical parameters connected to dynamics of flow and heat convection are explored from streamlines and isotherms graphs and discussed numerically in terms of Nusselt number. Findings The effect of the embedded heated square block size and its location in the enclosure, nanoparticles volume fraction and the intensity of the magnetic field on flow and heat transfer are computed. Compared with the case when no heated block is embedded in the enclosure, in free convection at Ra = 106, the average local Nusselt number on the wall-mounted heaters is attenuated by 8.25%, 11.24% and 12.75% when the enclosure embraced a heated square block of side length 10% of H, 20% of H and 30% of H, respectively. An increase in Hartmann number suppresses the heat convection. Research limitations/implications The enhancement in the convective heat is greater when the buoyancy effect dominates the viscous effects. Placing the embedded heated block near the inlet vent, the lower temperature zone has reduced while the embedded heated block is at the central location of the enclosure, the high-temperature zone has expanded. The external magnetic field can be used as a non-invasive controlling device. Practical implications The numerically simulated results for heat convection of water-based copper nanofluid agreed qualitatively with the existing experimental results. Social implications The models could be used in designing a target-oriented heat exchanger. Originality/value The paper includes a comparative study for three locations of the embedded heated square. The optimal results for the centrally located heated block are also performed for three different sizes of the embedded block. The numerically simulated results are compared with the published numerical and experimental studies.

Microstructure Evolution and Mechanical Properties Improvement in Magnetic-controlled Electroslag Remelted Bearing Steel

The transverse static magnetic field (TSMF) was introduced into the electroslag remelting (ESR) process to produce GCr15 steel ingots and the microstructure, non-metallic inclusions, chemical composition and mechanical properties of the ingots were analyzed to investigate the effect of TSMF during the ESR process. The transverse section of the ingots indicated that the application of a 130 mT static magnetic field resulted in a refined dendritic structure. The coverage ratio of the homogeneous crystallites area in the center of the transverse section increased to 52%. The metallic solid-liquid interface with different magnetic flux density (MFD) was recorded during ESR process. The depth of the metallic molten pool was 44.2 mm without the TSMF. When a 130 mT TSMF was applied, the molten pool became noticeably shallower (14.2 mm). And the oxide inclusions count in the scan area of 5.117 mm2 decreased to 239 from 1212. When the TSMF implemented, the tensile, friction and wear and Rockwell hardness properties of ingots showed a significant improvement. These results showed that the application of TSMF during the ESR process of GCr15 steel not only refine the dendritic structure, but also improve the efficiency of inclusion removal and mechanical properties.