Electromagnetic Body Force Research Articles

Unsteady Dean flow between concentric circular cylinders in the presence of a uniform axial magnetic field

An analysis is carried out on the unsteady Dean flow of an incompressible electrically conducting viscous fluid between two concentric, stationary permeable circular cylinders in the presence of magnetic field of low intensity. The flow phenomenon is important in view of its biological as well as industrial applications, particularly in polymer industries for designing flows in cylindrical shaped pipes/tubes. The novelty of the study is to analyze the effect of electromagnetic body force which comes into play due to interaction of magnetic field with conducting fluid in flow. The cross flow due to suction/injection, azimuthal pressure gradient, and the Lorentz force (electromagnetic body force) are considered in the momentum transport equation. The mathematical model and the corresponding governing equations are solved in two methods; one is analytical using special function and another one is semi analytical approach, i.e. Laplace transform in conjuction with Riemann–Sum approximation for inversion. The study reveals the effects of magnetic parameter, suction/injection parameter and radii ratio of two concentric cylinders forming annular region. The striking outcomes which fulfills the design requirements are as follows. The applied radial magnetic field resulting electromagnetic body force on the flow, accelerates the circumferential velocity which energizes the industrial setup (flow model) to enhance faster productivity. Moreover, the curves of skin friction at R = λ posses critical points serving as benchmark for engendering flow instability.

MHD peristaltic two-phase Williamson fluid flow, heat and mass transfer through a ureteral tube with microliths: Electromagnetic therapy simulation

The ureter typically experiences a frequency of one to five peristaltic contractions per minute. However, it is important to note that these contractions can be disrupted by various physical and mechanical irritants. Ionic contents in the urine make it electrically conducting and responsive to electromagnetic body forces. MHD can be deployed in bio magnetic therapy to control or mitigate symptoms associated with peristaltic pumping in the urinary system. This article therefore focuses on the hydromagnetic effects on flow patterns of urine with debris (monoliths). The mechanism of urine flow is largely coordinated by the kidneys. The flow inside the ureter is interrupted by microliths, which are generated by the sedimentation of excretory products. To simulate this, a two-phase formulation is adopted, comprising the electromagnetic urological viscous fluid phase and the particulate phase for solid grains. The peristaltic propulsion of two-phase liquid in the ureter is simulated as a sinusoidal wave propagation of incompressible non-Newtonian fluid. The Williamson viscoelastic model is deployed for the rheology. Heat transfer is also included with Soret thermo-diffusion and viscous heating effects. Long wave and low Reynolds number approximations are employed based on lubrication theory. The mass, momentum, energy and concentration conservation equations with associated boundary conditions are rendered non-dimensional via appropriate scaling transformations. A numerical solution is achieved via BVP4C MATLAB quadrature. Graphical visualizations of the velocity, temperature and concentration (solid grains) are given for the influence of suspension parameter ( ζ ), Hartmann number (M), Prandtl number (Pr), Weissenburg number (We), particle volume fraction (C), Eckert number (Ec), Soret number (Sr), Schmidt number (Sc). The novelty of the present work is therefore the simultaneous consideration of a generalized two-phase model, wall slip, non-Newtonian characteristics, cross diffusion, viscous dissipation, mass diffusion, magnetic body force and curvature effects in peristaltic urological transport, which has not been undertaken previously. The detailed simulations reveal that the flow velocity is reduced due to the presence of solid particles and the channel curvature, in comparison to the flow in an unobstructed channel devoid of solid particles. Enhancing the hydrodynamic slip parameter speeds up the movement of particles and fluid near the channel walls, boosts wall skin friction, raises pressure difference in the pumping area, and amplifies bolus magnitudes.The rise in peristaltic pumping results in a reduction in solid particle concentration, which is significant phenomena.This theoretical approach may aid in treating conditions such as Urinary Tract Infections (UTIs). The computations effectively demonstrate that significant manipulation of urological pumping characteristics can be achieved with an electromagnetic field. Some new features of two-phase ureteral dynamics are highlighted as relevant to magnetic therapy techniques, which may be beneficial to clinicians.

A complete physical 3D model from first principles of vibrational-powered electromagnetic generators

The dynamic behavior of a vibrational electromagnetic generator using a magnetic levitation architecture was theoretically and experimentally studied in great detail, when operating under a wide range of three-dimensional excitations. We developed a complete rigorous physical model from first principles based on the theory of electrodynamics of continua, centered on the laws of electrodynamics and balance of mass, linear momentum, angular momentum, energy and entropy. Local electromagnetic and gravitational body forces, couples and powers were considered, and the surface tractions were divided into constraint and friction components, as well as those due to external mechanical energy sources. The balance of linear momentum, angular momentum and circuit equations resulted in up to 13 non-linear differential equations describing the dynamics of the levitating-magnet and container, relating input forces and torques with output displacement, constraint forces and voltage. The balance of energy yielded a consistent equivalence between the time rate of change of the internal kinetic and potential energies of the generator and the output power, associated with the external circuit, Ohmic losses and friction losses, as well as the input mechanical power being supplied to the system by the environment. Both the input and output powers were proven to tend to increase equally when operating the generator under resonant conditions. The levitating generator was shown to be sensitive to axial translational and centrifugal inertial forces, each one effectively resulting in a uni-stable or bi-stable system. The dynamical response yielded multiple initial conditions dependent steady-states, hysteretic frequency output and chaotic characteristics. Relevant guidelines to optimize the energy conversion efficiency of energy harvesters are provided. This model was validated by experimental tests, including general 3D motions combining translations and rotations: cross-correlations exceeding 90% were achieved. Such Newtonian and Langrangian modelling approaches hold great potential to be easily adapted to a wide range of other electromagnetic generators, with multiple degrees-of-freedom and operating under various environments, such that significant advances in energy technologies can be supported.

Fracture behavior of superconductor REBCO tapes with multiple edge cracks under electromagnetic force

It is often necessary to narrow wide tapes through a slitting process in applications of the second-generation high-temperature superconductor REBa2Cu3O7-x (REBCO, RE = rare earth) tapes. However, this results in some random length edge cracks appearing on the slit edge and extending at certain angles towards the center of the tape. In this paper, we proposed a randomly distributed multiple-edge crack model to investigate the fracture mechanism of the superconducting tape under electromagnetic force due to high magnetic fields and current density (∼10 T and ∼ 1010A/m2). The electromagnetic body force distributions within the superconducting tape, incorporating multiple edge cracks, are simulated based on the H-formulation. Then a fracture analysis is conducted under the combined loading of tensile and electromagnetic forces, with the numerical calculation of stress intensity factors (SIFs) using the J-integral method. To validate the model's accuracy, we compare the body force distribution caused by an edge crack and the SIFs of edge cracks under uniform tension with existing results. Detailed analyses are undertaken to explore the impacts of electromagnetic body force non-uniformity, interactions between neighboring cracks, and the stochastic nature of geometrical parameters (length, angle, and spacing) on the fracture behavior under an alternating magnetic field. Numerical results indicate that non-uniform electromagnetic body forces arising from defects are a critical factor in crack propagation. Furthermore, the randomness of the geometrical parameters amplifies the interactions between some of the neighboring cracks, causing the tendency of the tape containing random edge cracks to fracture. Therefore, it is advisable to avoid random cracks with substantial length, angle, and spacing during the mechanical slitting process.

Mechanism of Electromagnetic Field in the Sub-RapidSolidification of High-Strength Al-Cu-Li Alloy Produced by Twin-Roll Casting

In this work, a Al-Cu-Li alloy plate with outstanding mechanical properties was successfully prepared with electromagnetic twin-roll casting (TRC) technology. The microstructure of Al-Cu-Li alloy manufactured by conventional mold casting, TRC, and electromagnetic TRC was studied in detail. The action mechanism of electromagnetic oscillation field (EOF) in the TRC process was studied by systematic experimental characterization and numerical simulation. The results show that the EOF will enlarge the circumfluence area in the cast-rolling zone, accelerate the mass transfer and heat transfer in the molten pool, and make the solute field and flow field in the liquid cavity tend to be evenly distributed. Further, the introduction of the EOF will produce the electromagnetic body force F with the maximum strength of 14 N/m3. The F acting on the solidification front will eliminate the accumulation and deposition of Cu2+, Li+, Mg2+, Zn2+, Mn2+ at the dendrite tip and inhibit the growth of dendrites. At the same time, the F can refine the microstructure of the TRC plate, promote the formation of equiaxed crystals, improve the supersaturated solid solubility of solute elements in the α(Al) matrix, and avoid the appearance of obvious solute segregation area or the formation of excessive solute enrichment area. Therefore, the macro-segregation in TRC plate was significantly reduced, the solidification structure was dramatically refined, and the comprehensive properties of the alloy were remarkably improved.

Study of Arrhenius activation energy on the thermo-bioconvection nanofluid flow over a Riga plate

This article deals with a study of Arrhenius activation energy on thermo-bioconvection nanofluid propagates through a Riga plate. The Riga plate is filled with nanofluid and microorganisms suspended in the base fluid. The fluid is electrically conducting with a varying, parallel Lorentz force, which changes exponentially along the vertical direction, due to the lower electrical conductivity of the base fluid and the arrangements of the electric and magnetic fields at the lower plate. We consider only the electromagnetic body force over a Riga plate. The governing equations are formulated including the activation energy and viscous dissipation effects. Numerical results are obtained through the use of shooting method and are depicted graphically. It is noticed from the results that the magnetic field and the bioconvection Rayleigh number weaken the velocity profile. The bioconvection Schmidt and the Peclet number decrease the microorganism profile. The concentration profile is enhanced due to the increment in activation energy and the Brownian motion tends to increase the temperature profile. The latter is suppressed by an increment of the Prandtl number.

Mechanical response induced by flux jump in a cylindrical superconductor

The flux jump in bulk superconductors is accompanied by a rapid change in temperature and magnetic field, which can induce change in electromagnetic bodyforce and thermal stress. It is well known that bulk superconductors are brittle and have low mechanical strength, and thus, large electromagnetic bodyforce and thermal stress can cause damage of the bulk superconductor. In this paper, an electromagnetic-thermal-mechanical multi-physics model is adopted to compute the mechanical response of a bulk superconductor during flux jump in an external magnetic field. The results indicate that the flux jump in the bulk superconductors can also lead to the jump of the average electromagnetic force, temperature, stress, and strain. Meanwhile, it can be found that the flux jump can occur more easily with a faster change in the magnetic field, a lower ambient temperature, and a large-size superconductor. The results also show that the peak value of thermal strain is much larger than the strain generated by electromagnetic bodyforce during the flux jump. In addition, the change in strain has the same trend as that of the temperature. Thus, the strain may also be used to monitor the flux jump.

Magnetoelastic buckling properties of type-II superconducting thin strip subjected to perpendicular magnetic field and parallel distributed uniform mechanical load

The buckling analyses of type-II superconducting strip under applied perpendicular magnetic field and/or distributed uniform mechanical load are investigated in this paper. Based on the Bean critical state model, the electromagnetic body force is firstly given. Then, based on the classical plate theory and two-point initial value method, the critical buckling states of the superconducting strip with different boundary conditions are analyzed. Numerical results show the effects of both the thickness and boundary conditions of superconducting strip on the corresponding critical buckling loads. The present work should be helpful to the research and application of superconducting thin strips.

Non-uniform stresses in thin high temperature superconducting films under electromagnetic force: General models of curvature-stress relations and experimental results

Strong flux pinning in high temperature superconducting (HTS) film has significantly boosted its capability of carrying high currents; however, it, in turn, induces huge electromagnetic force in the HTS film, and hence film stress evaluation under electromagnetic force is indispensable for assessing their reliability. In this work, first, an analytical model is presented for evaluating the electromagnetic-force-induced stresses in the thin HTS film that is placed in a vertical magnetic field. In this model, we relate curvatures to film stresses through electromagnetic body force, whose mechanism is very different from common film stress sources like misfit strain or thermo mismatch. The new model shows that the film stresses depend not only on the “local” curvatures at a same point of the substrate but also on the “nonlocal” curvatures of other points. Next, a coherent gradient sensor system for cryogenic measurement is implemented to monitor the stress states of the HTS film during the processes of magnetization and demagnetization. Finally, full fields of hoop stress, radial stress of the YBa2Cu3O7 − x film, and shear stress at interface between the film and the (00l) SrTiO3 substrate subjected to various magnetic fields are obtained, and all the stresses manifest irreversible behavior, which are first experimentally found in the thin HTS film-substrate system.

Heat Transfer Analysis of a Magneto-Bio-Fluid Transport with Variable Thermal Viscosity Through a Vertical Ciliated Channel

We communicate the responses of various physiological fluids containing hemoglobin and other ionic constituents when they propagate in the presence of an electromagnetic body force field with the mechanisms of heat generation and conduction. A fully developed mixed convective flow of a Newtonian fluid takes place through a 2D vertical channel in the presence of an external magnetic field acting in the direction normal to the flow. The inner surface of the channel is carpeted with a thick mat of cilia, which propagates a sinusoidal metachronal wave travelling in the direction of flow. Coupled, nonlinear governing Naiver-Stokes and temperature equations are simplified by utilizing the creeping flow and long wavelength approximations. This enables us to formulate the exact analytical solution of the temperature distribution; whereas, the velocity distribution is evaluated from the momentum equations by using the Adomian decomposition method. In order to determine the pumping characteristics, the formulae of volume flow rate and the pressure rise are also obtained. Trapping due to the ciliary system is highlighted by graphing the stream function. The findings of the present model have significant outputs, which can be applicable in the physiological transport of human semen through the male reproduction system.

Electromagnetic vortex suppression to prevent air core phenomenon for draining of electrically conducting liquids

The air core phenomenon observed during liquid suction or drainage through a narrow drain port can be reproduced artificially by starting the draining after rotating the cylindrical tank containing the liquid. Because the entrainment of gas-phase fluids during pump suction or liquid draining generates a breakdown of the machinery or defects in the product, various studies have been conducted to retard or prevent the air core phenomenon. Instead of utilizing an artificial structure such as a mesh or vane, as applied in previous studies, the present study introduces a new approach in which a magnetic field is applied to the container. First, the magnetic field applied induces an electric current through a reciprocal action with the liquid flow in the container. Next, the induced current and applied magnetic field create a Lorentz force, which is an electromagnetic body force. The Lorentz force helps with the suppression of existing flows. To couple the flow and electromagnetic fields, we solve the Poisson’s equation for the electric potential along with the momentum conservation. As the draining progresses, a volume-of-fluid (VOF) free surface capturing method is applied to track the free surface evolution, including the air core generation. For various Hartmann number (Ha) conditions, the internal velocities, vorticities, and Lorentz forces are comparatively presented. Finally, the effects of suppressing the air core phenomenon through the application of a magnetic field are discussed.

Effect of fractional derivatives on transient MHD flow and radiative heat transfer in a micro-parallel channel at high zeta potentials

By using the Caputo–Fabrizio time fractional derivative, unsteady flows of an incompressible viscous through a circular tube are developed. Flows are generated due to the combination of electroosmotic, pressure and magnetic forces. The derived fractional momentum equation incorporating the electromagnetic body force resulting from the electric double layer (EDL) field was solved using the Laplace transform technique, Riemann-sum approximation method, and the Stehfest’s algorithm. The solution obtained is validated by assenting comparisons between the Riemann-sum approximation method and Stehfest’s algorithm. Based upon the velocity field solution, the energy equation is analyzed by taking the viscous dissipation, thermal radiative, the volumetric heat generation due to Joule heating effect and electromagnetic couple effect into account. Numerical simulations and graphical illustrations were carried out using the software package Mathcad. The results highlights that, fractional models of fluid-flow and heat transfer with fractional derivatives bring significant differences compared to the ordinary model. The variations of fluid velocity, fluid temperature, skin friction and Nusselt number with related parameters are interpreted and the results are discussed.

Effect of Inclusions on Magnetostriction in Superconducting Cylinder with Exponential Distribution of Critical-Current Density

The magnetoelastic behaviour subjected to the electromagnetic body force induced by flux pinning is studied with Kim model for zero-field cooling (ZFC) magnetization process, in which the non-uniform parameter η is considered for inclusion-superconducting matrix system. For superconducting composites, the effect of inhomogeneous distribution of critical current density on effective magnetostriction is also obtained based on the plane strain approach. The results show that the exponential distribution of critical-current density will lead to a larger trapped field and magnetostriction inside the inhomogeneous sample, which also means that it is worthwhile to investigate the magnetoelastic problem of bulk superconductors with inhomogeneous distribution of critical-current density.

Magnetic field advection in a rotating magnetic field driven flow induced by a non-ideal inductor

The limits of the axisymmetric ideal inductor approach and the low magnetic Reynolds number (Rem) approach are demonstrated for the case study of a flow driven by a rotating magnetic field induced by an explicit-pole non-ideal inductor. These effects are studied for an intermediate range of the magnetic Reynolds number 0.1 ≤ Rem ≤ 1. It is shown that phenomena that do not exist under the ideal inductor approach change the distribution of the electromagnetic body force (EMBF) from axial symmetry to rotational symmetry. However, it is found that the magnetic field advection (MFA), which is neglected under the low Rem approach, induces body force that changes the distribution of the EMBF so that it effectively becomes closer to being axisymmetric. Therefore, it is suggested that the ideal inductor approach should not be applied in low Rem applications; this approach can be applied in high Rem applications. It is also found that the effect of MFA on the averaged velocity field is negligible for higher values of Rem than traditionally assumed, but MFA has a significant effect in reducing the turbulent kinetic energy. The reduction is found to be a result of the MFA-induced EMBF reducing the turbulence production.

Stability and structures in atmospheric pressure DC non-transferred arc plasma jets of argon, nitrogen, and air

The stability of dc non-transferred arc plasma jets and their internal structures is investigated through fast photography, emission spectroscopy, and arc dynamics under different operating conditions. A novel method to explore structures inside extremely intense hot plasma jet is conceived and applied for the first time to investigate arc plasma jets. The study revealed distinct interesting structures and their evolution inside the plasma jet, apparently not reported earlier. The associated fundamental mechanisms are identified from direct experimental evidences. Respective steady state jet characteristics with and without air entrainment are obtained from computational fluid dynamic simulation. Arc root motion, air entrainment, and interaction between electromagnetic and fluid dynamic body forces are found to result in a variety of interesting dynamics and structures inside the plasma jet under different operating conditions. Observed behaviors are notably different in argon, nitrogen, and air plasma. While no unusual structures are found over a range of lower flow rates, interesting structures evolve at higher flow rates. Statistical behavior of these structures is found to have a significant dependence on the gas flow rate and torch power. Apart from air entrainment in the downstream, observed isolated temperature islands inside the jet in the upstream have potential to affect particle trajectory, physical processes, and process chemistry in a significant manner.

The position dependence of fracture behavior in a superconductor/ferromagnetic bilayer strip

The effect of crack position and length on the fracture behavior in the superconductor/ferromagnetic (SC/FM) bilayer strip is investigated with finite element method. Owing to the composite structure of the SC/FM hybrids, the electromagnetic body force acting on the SC/FM bilayer strip will lead to complicated mechanical deformation during magnetization. The crack is prone to propagate even in the field ascent stage when the crack gets close to the sample bottom, which is quite different from the feature in a single SC sample. Moreover, the crack length and position leads to two inverse variations of stress intensity factor (SIF). SIF is positive and has peak value in the intermediate stage of field reduction when crack is close to superconducting layer. By contrast, SIF is positive except the intermediate stage and has maximum value at the beginning of the descent stage. Such novel behavior of SIF versus applied field can be explained by the strain distribution along the thickness direction for various crack positions. Generally, the maximum SIF at the maximum applied field is much larger than that in the field descent stage. The fracture behavior at the upper tip and lower tip exhibits significantly different characteristics. The maximum SIF at the lower tip is much larger than that at the upper tip as the crack is sufficiently close to the bottom surface.

Edge-Based Finite Element Formulation of Hypersonic Flows Under an Imposed Magnetic Field

The paper presents an edge-based finite element method for the simulation of three-dimensional hypersonic flows subject to an imposed magnetic field. Under the magnetogasdynamics assumptions and at low magnetic Reynolds numbers, a current continuity equation is employed instead of the system of Maxwell equations to obtain the induced electric field. The flow can be modeled by the Reynolds-averaged Navier–Stokes equations, and the electromagnetic body force and joule heating resulting from the imposed magnetic field introduced through source terms. Both inviscid and viscous flows over a sphere, as well as an Apollo-like reentry capsule geometry, are used to validate the approach. For both geometries, inviscid and viscous results show that the shock standoff distance increases with the magnetic-field intensity, whereas the heat flux at the stagnation point decreases. Moreover, it is observed that the induced electric field has a substantial impact on the effectiveness of magnetohydrodynamic heat shield and cannot be neglected in the calculations. An anisotropic mesh adaptive mesh methodology is used to refine the results and to demonstrate grid independence.

Real-time stress evolution in a high temperature superconducting thin film caused by a pulse magnetic field

The high temperature superconducting YBa2Cu3O7−x films are widely used in various classes of microwave devices and these structures often undergo pulse magnetic field in applications. The stress behavior is of relevance to understand the mechanical response and important for assessing the safety of these superconducting structures. In this paper, we construct a theoretic model to analyze the stress behavior of a superconducting thin film-substrate system under a pulse loading (magnetic field), which is different with the well-known theoretic framework based on the Stoney formula. In the case of radial symmetry, the relationship between the stress of thin film and the electromagnetic body force is derived analytically. When a pulse loading is exerted on this film-substrate system, an analytical expression of stress dependent on the film curvature is presented, which can be considered as the foundation for the further experimental measurement. Moreover, we extend the coherent gradient sensor to kinetic measurement of the full field curvature. Using the presented model and the experimental technique, the full field stress and its evolution with time of a superconducting thin film-substrate system under a pulse magnetic field are obtained.

Global simulation of the induction heating TSSG process of SiC for the effects of Marangoni convection, free surface deformation and seed rotation

A global numerical simulation was performed for the induction heating Top-Seeded Solution Growth (TSSG) process of SiC. Analysis included the furnace and growth melt. The effects of interfacial force due to free surface tension gradient, the RF coil-induced electromagnetic body force, buoyancy, melt free surface deformation, and seed rotation were examined. The simulation results showed that the contributions of free surface tension gradient and the electromagnetic body force to the melt flow are significant. Marangoni convection affects the growth process adversely by making the melt flow downward in the region under the seed crystal. This downward flow reduces carbon flux into the seed and consequently lowers growth rate. The effects of free surface deformation and seed rotation, although positive, are not so significant compared with those of free surface tension gradient and the electromagnetic body force. Due to the small size of the melt the contribution of buoyancy is also small.

Guideline for Forming Stiffened Panels by Using the Electromagnetic Forces

Electromagnetic forming (EMF), as a high-speed forming technology by applying the electromagnetic forces to manufacture sheet or tube metal parts, has many potential advantages, such as contact-free and resistance to buckling and springback. In this study, EMF is applied to form several panels with stiffened ribs. The distributions and variations of the electromagnetic force, the velocity and the forming height during the EMF process of the bi-directional panel with gird ribs are obtained by numerical simulations, and are analyzed via the comparison to those with the flat panel (non-stiffened) and two uni-directional panels (only with X-direction or Y-direction ribs). It is found that the electromagnetic body force loads simultaneously in the ribs and the webs, and the deformation of the panels is mainly driven by the force in the ribs. The distribution of force in the grid-rib panel can be found as the superposition of the two uni-directional stiffened panels. The velocity distribution for the grid-rib panel is primarily affected by the X-directional ribs, then the Y-directional ribs, and the variation of the velocity are influenced by the force distribution primarily and secondly the inertial effect. Mutual influence of deformation exists between the region undergoing deformation and the deformed or underformed free ends. It is useful to improve forming uniformity via a second discharge at the same position. Comparison between EMF and the brake forming with a stiffened panel shows that the former has more advantages in reducing the defects of springback and buckling.