The heating and melting of reactive alloys in a cold crucible are considered in this study to produce a continuous melt stream as feed to a gas atomiser. A pre-heated rod of material enters the crucible at a rate equal to the amount of mass leaving as a liquid stream through the outlet. An induction coil is used to melt the contents of the crucible, which then pours out as a stream to enter a gas atomizer. The outlet nozzle may be controlled using an induction valve, operating at a different AC frequency. The concept is tested through simulations using titanium and a nickel superalloy as model materials. Tables 1, Figs 10, Refs 8.
A numerical simulation of silicon crystal growth in a specific Czochralski furnace was carried out. The experimental process involves a melting stage, a holding stage to homogenize the melt by electromagnetic stirring and, finally, a solidification stage by pulling the seed upwards to obtain a single crystal. Enthalpy formulation with moved and deformed mesh technique is used for numerical simulations of the phase-change problems. However, only the stage of solidification under the effect for forced convection driven by an external travelling magnetic field was numerically investigated. The proposed numerical model has demonstrated its effectiveness in predicting the effect of electromagnetic stirring on the solidification process in terms of thermal field, dynamic field and shape and localization of the solidification front. Unfortunately, due to the lack of experimental measurements, the results obtained by numerical simulation have not been yet validated. Tables 1, Figs 7, Refs 14.
A design of a new type of liquid metal electromagnetic pump for medium flowrates and moderate pressure heads has been developed. The major difference compared to existing concepts is that the central iron core, which closes the magnetic flux lines, is fabricated from a single iron piece, which may freely rotate in order to avoid magnetization losses. The pump was designed and manufactured at KIT and tested in the liquid metal NaK loop of the MEKKA facility. Its performance curve (pressure head vs. flowrate) and efficiency have been determined for a variety of frequencies and magnitudes of applied 3-phase current. Figs 7, Refs 8.
This study investigates the influence of a non-uniform static magnetic field on bubble dynamics during cavitation, focusing specifically on bubble oscillation. Using a numerical simulation approach, we applied a magnetic field to a low pressure bubble inside a large volume of fluid to follow oscillation of the bubble's radius neglecting liquid--gas mass exchange. Our simulations showed impacts of the magnetic field on the bubble dynamics slightly affecting the minimum bubble radius and implosion dynamics. This modification might be related to the shock wave modification. Figs 4, Refs 23.
This study investigates a high-flowrate, multi-channel electromagnetic permanent magnet pump (EMP) by comparing experimental and numerical results obtained using an electrical potential (inductionless) method. Experimental data, including pressure, flowrate, power, temperature, and magnet system rotation speed, were collected using EMP in the TESLA-EMP loop at the Institute of Physics, University of Latvia (IPUL) in Salaspils. A numerical calculation under linebreak the same conditions was performed using the COMSOL Multiphysics commercial software. A steady-state MHD calculation, employing the k-ε turbulence model while neglecting the induced magnetic field was performed. The results indicate qualitatively good agreement in the developed pressure under insulating inner wall conditions, suggesting a poor electrical contact between the sub-channels and a relatively low slip magnetic Reynolds number. Figs 9, Refs 4.
This work considers the translation of a solid sphere in a conducting Newtonian liquid, bounded by a cylindrical solid and motionless tube with a radius R, subject to a prescribed ambient magnetic field B. The sphere, with a radius a, has its center located on the tube axis which is parallel to both B and the sphere velocity. Assuming vanishing Reynolds and magnetic Reynolds numbers, the liquid flow about the sphere, axisymmetric and without swirl, obeys quasi-steady Stokes equations with a Lorentz body force. The stress arising on the sphere surface and the liquid flow are here obtained by truncating the fluid domain, solving coupled boundary-integral equations for the stress axial and radial components and using integral representations for the flow pressure and axial and radial velocity components. A boundary element method is employed to numerically get the drag exerted on the sphere and the flow about it. Both depend on the tube normalized radius R/a and the problem Hartmann number Ha = a/d, where d is the Hartmann layer thickness. The numerical implementation is presented and the computed drag and flow patterns are reported for some settings (R/a,Ha). It is found that, in contrast to the unbounded liquid case, the drag is weakly sensitive to Ha for small Ha and a region of reverse flow takes place near the tube boundary. Tables 3, Figs 5, Refs 14.
This paper deals with a permanent magnet induction pump and presents a new numerical1model of this pump. The fully coupled transient problem is considered. At each time step, an 2 electromagnetic computation updates the electromagnetic force field in the fluid and feeds it3to the transient fluid dynamic computation, which in turn updates the velocity field needed to4update the electromagnetic computation at the next time step, and so on. The results obtained5with this new model are validated by an experimental study of the recent literature and briefly6compared to others numerical models of the literature. This new model has the advantage of7being able to predict pressure fluctuations for fatigue analyses and minimum pressure zones for8cavitation risk assessment.
This work studies the convection phenomenon of two differentfluids confined in a cubic cavitywith a side length of 50 mm. Experiments with water and GaInSneutectic alloy are conductedby heating and cooling the bottom and top lids, respectively. Temperature differences of 2, 4,6, and 8 K are imposed between both lids to study convective flows. Particle image velocimetryand ultrasonic Doppler velocimetry techniques are used to measure water flows, whereas forGaInSn only ultrasonic Doppler can be used. Additionally, anumerical study was conductedusing the ANSYS Fluent software. Experiments and simulations predict time-dependent flowpatterns for both fluids. Maximum velocity values for water and GaInSn are up to 6 and12 mm/s, respectively. Values for GaInSn are in the same order of magnitude as those obtainedfor electrovortex flows in the same configuration
An effect of the DC magnetic field directed horizontally and imposed over an electromagneticallylevitating droplet of liquid metal is studied via temperature measurements at the equatorial andpolar parts of the droplets of Ni and Cu. It is demonstrated that while the application of the DCmagnetic field lower than 3.5 T destabilizes the droplet, a DCmagnetic field of 4.5 T stabilizesthe position of the droplet that provides less noisy temperature measurements. However, thereis no clear evidence of the damping of the convective heat transport inside the droplet.
An experimental electrolyte flow inside a cylindrical cavity promoted by a Lorentz force createdby external electric currents and a magnetic field applied inthe axial direction is discussed. TheLorentz force produces an azimuthal swirling flow that givesrise to a secondary poloidal flow.Supported by numerical simulations we found that a three-dimensional flow can be interpretedas being partially composed by toroidal orbits. The flows studied have common features withelectrovortex flows, and it is expected that this study can contribute to their understanding.
The heating and melting of reactive alloys in a cold crucible are considered in this study to produce a continuous melt stream as feed to a gas atomiser. A pre-heated rod of material enters the crucible at a rate equal to the amount of mass leaving as a liquid stream through the outlet. An induction coil is used to melt the contents of the crucible, which then pours out as a stream to enter a gas atomizer. The outlet nozzle may be controlled using an induction valve, operating at a different AC frequency. The concept is tested through simulations using titanium and a nickel superalloy as model materials.
Liquid metal flow through a circular pipe forming a U-bend is investigated numerically fora constant Reynolds number when a uniform magnetic field is imposed. The influence of theintensity of the applied magnetic field on the flow pattern, pressure and electric current distri-bution is studied via 3D numerical simulations. It is found that when the magnetic field is weak,a spiral motion develops that is fed mainly by the fluid movingin the boundary regions. Byincreasing the magnetic field, the stronger electromagnetic forces weaken the vortical flow andsignificantly affect flow features leading to the formation ofan internal field-aligned fluid layertangent to the inner side of the bend. This layer carries thenmost of the flow
This study investigates the influence of a non-uniform static magnetic field on bubble dynamicsduring cavitation, focusing specifically on bubble oscillation. Using a numerical simulationapproach, we applied a magnetic field to a low pressure bubbleinside a large volume of fluid tofollow oscillation of the bubble's radius neglecting liquid-gas mass exchange. Our simulationsshowed impacts of the magnetic field on the bubble dynamics slightly affecting the minimumbubble radius and implosion dynamics. This modification might be related to the shock wavemodification
A numerical simulation of silicon crystal growth in a specific Czochralski furnace was carriedout. The experimental process involves a melting stage, a holding stage to homogenize themelt by electromagnetic stirring and, finally, a solidification stage by pulling the seed upwardsto obtain a single crystal. Enthalpy formulation with movedand deformed mesh techniqueis used for numerical simulations of the phase-change problems. However, only the stage ofsolidification under the effect for forced convection drivenby an external travelling magnetic fieldwas numerically investigated. The proposed numerical model has demonstrated its effectivenessin predicting the effect of electromagnetic stirring on the solidification process in terms of thermalfield, dynamic field and shape and localization of the solidification front. Unfortunately, due tothe lack of experimental measurements, the results obtained by numerical simulation have notbeen yet validated
A theoretical and numerical study on the dynamics of a spherical droplet of liquid metal in zero-gravity conditions in the presence of a uniform magnetic field is presented. The droplet is initially deformed into an ellipsoidal shape and then released so that it oscillates until it recovers a spherical shape. The strength of the applied magnetic field is modulated to analyze the damping process of the oscillating droplet. An analytical solution is obtained describing the free surface evolution of the droplet considering magnetohydrodynamic effects in the creeping flow regime. A numerical simulation of the oscillating droplet is implemented by solving the three-dimensional problem using the Smoothed Particle Hydrodynamics method. The analytical and numerical results agree qualitatively and quantitatively.
An AC single plasma actuator has been developed using a magnetic fluid (MF) and a dielectricbarrier discharge (DBD), termed "single MF-DBD plasma actuator". In this system, the DBDinduces an ionic wind from the MF, which is held in place by an external magnetic field. Thisstudy investigates the effect of an external magnetic field onthe ionic wind velocity. Theexperimental results indicated that the external magneticfield effectively controls the ionicwind velocity due to the interaction between the MF and the exposed electrode. The efficiencyof the ionic wind generation is also analyzed and clarified.
The combined effects of magnetic field and thermal radiation on the fluid flow and heat transfer characteristics of two-dimensional Rayleigh-Benard convection in molten salt are investigated numerically by using a collocation spectral method. A series of simulations are carried out for Rayleigh numbers between 10(5 )and 10(6), Hartmann number ranging from 30 to 100, and with the radiation-conduction parameter fixed between 0.5 and 4,respectively. For the computation of radiation field, we start from a simple model, named the linear Rosseland approximation[1], which assumes that the radiative heat flux is mainly diffusive and proportional to the temperature gradient. The results show that the convective heat transfer along the bottom wall is weakened under the combined influences of both magnetic field and thermal radiation. However, depending on the actual values of the parameters, the overall convective heat transfer and fluid flow can be either enhanced or suppressed under the combined effects.
This study investigates a high-flowrate, multi-channel electromagnetic permanent magnet pump (EMP) by comparing experimental and numerical results obtained using an electrical potential (inductionless) method. Experimental data, including pressure, flowrate, power, temperature, and magnet system rotation speed, were collected using EMP in the TESLA-EMP loop at the Institute of Physics, University of Latvia (IPUL) in Salaspils. A numerical calculation under the same conditions was performed using the COMSOL Multiphysics commercial software. A steady-state MHD calculation, employing the k-e turbulence model while neglecting the in- duced magnetic field was performed. The results indicate qualitatively good agreement in the developed pressure under insulating inner wall conditions, suggesting a poor electrical contact between the sub-channels and a relatively low slip magnetic Reynolds number.
This work considers the translation of a solid sphere in a conducting Newtonian liquid, boundedby a cylindrical solid and motionless tube with a radiusR,subject to a prescribed ambientmagnetic fieldB. The sphere, with a radiusa, has its center located on the tube axis which isparallel to bothBand the sphere velocity. Assuming vanishing Reynolds and magnetic Reynoldsnumbers, the liquid flow about the sphere, axisymmetric and without swirl, obeys quasi-steadyStokes equations with a Lorentz body force. The stress arising on the sphere surface and theliquid flow are here obtained by truncating the fluid domain, solving coupled boundary-integralequations for the stress axial and radial components and using integral representations for theflow pressure and axial and radial velocity components. A boundary element method is employedto numerically get the drag exerted on the sphere and the flow about it. Both depend on thetube normalized radiusR/aand the problem Hartmann number Ha =a/d, wheredis theHartmann layer thickness. The numerical implementation ispresented and the computed dragand flow patterns are reported for some settings (R/a,Ha).It is found that, in contrast to theunbounded liquid case, the drag is weakly sensitive to Ha forsmall Ha and a region of reverseflow takes place near the tube boundary
A relativistic field theory of inhomogeneous and anisotropic matter and radiation with a mathematical manifold structure should account for an impersonal picture of the world and contact with physical observables. To incorporate in the theory the interacting nature of microscopic and macroscopic constituents presents philosophical, physical, and mathematical issues. Such a field theory of gravitation and electromagnetism can be motivated by averaging the constituents of fine-grained space-time regions, but a gauge-independent theory of the averaged intrinsic tensor fields defined on a coarse-grained mathematical manifold with structure can only be deduced and closure of the fields established by a relativistic theory of constitutive equations.
