Effect Of Lorentz Force Research Articles

Experimental investigation of the electromagnetic acceleration mechanisms in an Applied-field Magnetoplasmadynamic Thruster

Abstract The high specific impulse and efficiency of the applied-field magnetoplasmadynamic thruster make it one of the most promising electric thrusters in deep space exploration. However, the crucial electromagnetic acceleration mechanisms are still not clearly investigated, which limits performance improvement. The electromagnetic acceleration mechanism is closely related to the current path and magnetic field distribution in the plume. Experiments are conducted using a water-cooled Hall probe in the steady-state applied-field magnetoplasmadynamic thruster plume. The radial, azimuthal and axial magnetic fields are measured, then the current density and Lorentz force density are calculated. The results show that the outflow current accounts for 63% to 82% of the thruster discharge current depending on the strength of the applied magnetic field. Moreover, the outflow current can extend the range of electromagnetic force action, which in turn increases the effect of electromagnetic acceleration. The radial Lorentz force is numerically dominant, and the combined effect of the radial Lorentz force and axial Lorentz force is to compress the plasma toward the axis. In electromagnetic acceleration, Self-field contributions are less than 5%, while E × B acceleration constitutes -12.2-21.2%, and Diamagnetic acceleration dominates at approximately 76.7-90.5%. Finally, a method for evaluating the rotational velocity was presented based on the MHD equations. The centrifugal force was then calculated by combining this with the plasma density. At the thruster outlet, the centrifugal force is significant and cannot be ignored in comparison to the radial Lorentz force.

Study on the effect of Lorentz force on the nuclear reactor core melt stratification in electromagnetic cold crucible

To understand the effect of the Lorentz force on core melt stratification during experiments, a multi-physical field coupling model of electromagnetic induction, non-isothermal flow, and two-phase flow is established in this paper. The evolution of the layered core melt in the electromagnetic cold crucible is studied for different relative densities and phase volume fraction ratios between metal and oxide. The calculation results show that the coupling model can accurately describe the structural evolution of core melt. The Lorentz force cannot change the relative positions of the metal and oxide, but it can significantly affect the morphology of the core melt. If the density of the metal is less than that of the oxide, the Lorentz force causes the light metal with a small phase volume fraction to form a hemispherical shape in the top center of the crucible. As the phase volume fraction increases, the Lorentz force become weaker than those of gravity and buoyancy. The light metal is then flat. When the metal density is greater than the oxide density, the Lorentz force causes the heavy metal with a small phase volume fraction to appear as a hemisphere, but causes the heavy metal with a large phase volume fraction to appear as an ellipsoid in the lower part of the crucible.

Two branches solutions for mixed convection flow of thermally Williamson nanofluid flow with heat transfer due to magnetized shrinking sheet

AbstractThe study of magnetohydrodynamics (MHD) and thermal radiation over‐stretching and shrinking sheets has significant applications in a wide range of fields, from chemical manufacturing to transport engine cooling systems, electronic chip cooling, plasma, the nuclear‐powered sector, saltwater, etc. The present study aims to numerically and theoretically analyze the movement of thermally magnetized Williamson nanofluid owing to an extended/contracting sheet. The regulating flow equations are converted to self‐similar equations through similarity transformation, and then numerically solved by bvp4c using MATLAB software. A comparison of the present numerical study with the published study is quite impressive. The investigation demonstrates that the self‐similar equations disclose the two branches for the limited shrinking factor range. For the stretching case, only one solution exists. As a result, the most fundamentally feasible solution has been determined by the linear assessment of temporal stability. For the aim of stability analysis, the lowest eigenvalue sign indicates the stability or instability of a solution. Through stability analysis, it is witnessed that the first solution (first branch) is stable. Due to the presence of the Lorentz force effect, it is perceived that the velocity curves decline in the whole channel. The point to be noted here is that the velocity of the lower branch compared to the upper branch is higher. The reduced Skin Friction is increased in the first branch and declines in the second branch for the two different values of magnetic factor.

Research on Auxiliary Effect of Lorentz Force for On-orbit Servicing of Spacecraft

Background: On-orbit servicing of spacecraft is mainly aimed at repairing failed spacecraft, maintaining and upgrading normally operating spacecraft to extend their life in order to reduce the increase of space debris and maintain the space environment. Objective: In performing on-orbit servicing, the spacecraft typically requires continuous control force to hover for a long period of time in order to maintain a relatively stationary state towards the target. Methods: Considering the limited amount of fuel carried, the Lorentz force is introduced into onorbit servicing to assist spacecraft in hovering. In order to demonstrate the feasibility of using Lorentz force as spacecraft thrust, many related patents have been provided. Results: Firstly, the velocity of the spacecraft's orbital motion and the variation of the geomagnetic field were given, and the specific expression of the Lorentz force in the relative dynamics model of the spacecraft was deduced. When studying the auxiliary effect of Lorentz force, a critical angle was defined. The relation between the critical angle and the Lorentz force on the auxiliary effect of spacecraft hovering was analyzed through numerical examples. Conclusion: Furthermore, based on the influence of the charge-to-mass ratio on the critical angle, the variation law of the Lorentz force-assisted spacecraft hovering area with different charge-tomass ratios was derived.

Effect of Coriolis force on electrical conductivity tensor for the rotating hadron resonance gas

We have investigated the influence of the Coriolis force on the electrical conductivity of hadronic matter formed in relativistic nuclear collisions, employing the hadron resonance gas model. A rotating matter in the peripheral heavy-ion collisions can be expected from the initial stage of quark matter to late-stage hadronic matter. Present work is focused on rotating hadronic matter, whose medium constituents—hadron resonances—can face a nonzero Coriolis force, which can influence the hadronic flow or conductivity. We estimate this conductivity tensor by using the relativistic Boltzmann transport equation. In the absence of Coriolis force, an isotropic conductivity tensor for hadronic matter is expected. However, our study finds that the presence of Coriolis force can generate an anisotropic conductivity tensor with three main conductivity components—parallel, perpendicular, and Hall—similarly to the effect of Lorentz force at a finite magnetic field. Our study has indicated that a noticeable anisotropy of conductivity tensor can be found within the phenomenological range of angular velocity Ω=0.001–0.02 GeV and hadronic scattering radius a=0.2–2 fm. Published by the American Physical Society 2024

(Invited) The Influence of Magnetic Fields on the Oxygen Evolution Reaction Catalyzed By Cobalt-Iron Oxide Nanowire Arrays

To mitigate climate change through the establishment of a renewable energy infrastructure, advancements in energy storage technologies are imperative. Electrochemical water splitting via electrolyzers enables the conversion of electrical energy into chemical energy. However, the performance of these devices, particularly that of the oxygen evolution reaction (OER) occurring at the anode, still needs to be improved. Previous studies have demonstrated that magnetic fields can induce convective flow to the electrode through Lorentz and Kelvin force effects, thereby improving the mass transport.[1] In contrast to the Lorentz force, the Kelvin force can be substantially increased by introducing magnetic nanostructures to create high magnetic field gradients in the vicinity of the electrode surface.[2] Given the magnetic properties inherent to many earth-abundant metal-based and nanostructured electrocatalysts promising for the OER, there is potential for intelligently designing electrodes to leverage magnetic field effects in the future. However, a comprehensive understanding of these magnetic field effects is currently lacking. In the scope of this work, we aimed to systematically investigate the influence of magnetic fields on the oxygen evolution reaction. Considering the substantial magnetic field gradients generated by magnetic nanowires, we fabricated arrays of freestanding cobalt-iron oxide nanowires to explore the influence of magnetic fields on the oxygen evolution reaction catalyzed by these nanostructured electrocatalysts. Templated electrodeposition of cobalt-iron alloy into the pores of anodic aluminum oxide membranes enabled a straightforward control over nanowire diameter and length. Subsequent removal of the aluminum oxide template in alkaline solution yielded cobalt-iron oxide nanowires composed to 60% of Fe and 40% of Co standing freely on an electrochemically stable gold substrate. Superimposing a magnetic field during water oxidation on the so-prepared nanowire arrays resulted in an increase in the measured oxidation current (see Figure). To deconvolute the contributions of the Lorentz and Kelvin force, experiments were conducted in two different magnetic field orientations: either parallel or perpendicular to the electrode surface. In the parallel orientation, a linear correlation between the increase in current and the strength of the applied magnetic field was observed. In contrast, when the magnetic field was aligned perpendicular to the electrode surface, a plateau in the current enhancement manifested at higher magnetic field strengths, indicating different dominant effects in the two configurations.[1] K. Ngamchuea, K. Tschulik, R. G. Compton, Magnetic control: Switchable ultrahigh magnetic gradients at Fe3O4 nanoparticles to enhance solution-phase mass transport, Nano Res. 2015, 8, 3293–3306.[2] L. M. Monzon, J. Coey, Magnetic fields in electrochemistry: The Kelvin force. A mini-review, Electrochem. commun. 2014, 42, 42–45. Figure 1

Modulating photocatalytic activity of nitrogen doped TiO2 nanoparticles via magnetic field

The effect of the magnetic field on the photocatalytic activity of TiO2-based nanoparticles is analyzed using a magnetically-assisted photoreactor with permanent magnets to generate a controlled uniform magnetic field, B (≈ 82 mT). Nitrogen doped TiO2 nanoparticles (sizes around 10 nm) were synthesized through a solvothermal method employing Ti(IV) butoxide and HNO3 (x = 0, 0.5, 1, 1.5 and 2 mL) as precursors and their structural, optical and magnetic properties were analyzed. Specifically, nitrogen doping is confirmed through Hard X-ray Photoelectron Spectroscopy (HAXPES) in those samples synthesized with low HNO3 concentrations (x = 0.5, 1). The correlation between spin polarization (magnetic susceptibility) and visible photocatalytic activity (methyl orange as a model organic pollutant) is particularly analyzed. Surprisingly, opposite effects of the magnetic field on the photocatalytic performance are found in the visible range (above 400 nm) or under UV-Vis irradiation (decrease and increase in the photocatalytic activity, respectively, under magnetic field). The Langmuir-Hinshelwood model allows us to conclude that the strong decrease in adsorption under the magnetic field (around 42 % for x = 0.5) masks the increase in the kinetic constant (close to 58 % for x = 0.5) related mainly to the effect of Lorentz forces on the reduction of the electron-hole recombination.

Numeral simulation of solution mixing effect and product preparation effect in the process of preparing cerium oxide by microwave heating

Microwave heating has the characteristics of simple control and high efficiency, in which electromagnetic force plays an important role. Using the UDF function and energy equation in FLUENT software, the electromagnetic force model in the tube is established. The mixing process of cerium chloride solution under different heating modes, the mixing effect of Lorentz force and the preparation process of cerium oxide under different inlet material velocities were numerically simulated. CFD-Post and MATLAB software are used to post-process the data of the whole fluid area. Through the above analysis, the best process conditions of numerical simulation and experiment are finally determined. The results show that microwave heating has better mixing effect and lower material loss compared with conventional heating, in which electromagnetic force plays a promoting role; Under the condition of microwave heating, the product conversion rate is high, and the concentration of cerium oxide is high and distributed evenly. The more appropriate mixing method of cerium chloride and preparation method of cerium oxide are microwave heating, and the more appropriate inlet velocity of materials is 0.15 m/s.

Aspects of double slip on multiphase inclined channel flow of Casson and Cu-nanofluid

The key aspect of this study is to inspect the entropy generation (EG) of heat and momentum transport within two immiscible Casson and nanofluid (NF) with mass diffusion of copper nanomaterials in an inclined channel (IC) with thermal and velocity slips. The IC is divided into two regions. Region-I contains the Casson fluid (CF) whereas Region II is occupied with copper-water NF. Moreover, the effects of Lorentz force are also taken in region II having copper-water NF. The mathematical model is solved by employing the perturbation method. The behavior of different aspects, i.e., mass diffusion of copper nanomaterials, Lorentz force, velocity and thermal slips on EG, and transport of mass and heat are presented in graphs and tabular forms. Furthermore, the numerical outcomes of friction at the walls and the rate of heat transport are presented in tabular form. Our results show that the EG and the rate of EG decline when the dispersion of nanomaterials is increased. The velocity and temperature decline when Lorentz force is increased in Region II. Furthermore, temperature augments with the rise in CF parameter and thermal slip parameters whereas velocity also increases with the rise in velocity slip parameters. So, the thermal performance can be enhanced in an IC by using blood fluid in one phase and thermal slips at the walls.

Analysis of MHD third-grade hybrid nanofluid model in Darcy-Forchheimer porous medium: Evaluation of the thermal performance of [formula omitted]-[formula omitted] cylindrical nanoparticles dispersed in ethylene glycol fluid

Researchers and scientists became interested in the newly developed idea of hybrid nanofluids because of their exceptional thermal conductivities, which resulted in enhanced thermal performance. These fluids have a wide range of uses in the industrial and technical fields. This novel class of fluids is playing a vital role in solar energy, automotive industry, cooling of the machine and manufacturing, heating and ventilation systems, electronic cooling, nuclear systems cooling, biomedical fields, space, ships, and defense systems. In light of the physical significance of the above-mentioned class of fluids, the current investigations are carried to examine the thermal performance of the mixture of cylindrical shaped aluminum oxide Al2O3 and copper Cu nanoparticles suspended in ethylene glycol using third-grade non-Newtonian fluid flow model. The fluid flow is induced by the stretching of the permeable sheet in exponential manner that is embedded in a Dacry-Forchheimer porous medium. The effects of Lorentz force applied normal to the flow and suction impacts have been incorporated in the current proposed model. The solutions of the flow model transformed to ordinary differential equations are computed using MATLAB built-in solver bvp4c. The solutions are presented in graphical representations. Graphical solutions reflect that fluid velocity slows down by growing the volume fractions of the nanoparticles. Increasing values of viscoelastic parameters reflect that there is a reduction in velocity and intensification in profiles of temperature and concentration have been noted. Rising values of cross-diffusion parameter is leading to the reduction in magnitude of velocity, and augmenting behavior of temperature and concentration has been seen. Observations indicate rising third-grade fluid parameter and porosity parameter lead to reduction in velocity. Increasing Schmidt number gives reduced Sherwood number, and magnetic field parameter improves the rate of hear transfer (Nusselt number) and skin friction coefficient for both Al2O3/ethylene glycol nanofluid and Al3O3-Cu/ethylene glycol-based hybrid nanofluid. The suggested model's validity is confirmed through comparison with previously released findings. Additionally, a grid independence test (sensitivity analysis) has been performed to verify the accuracy and verification of the numerical model.

Computational Analysis of Magneto Bioconcvection Casson Nanofluid Flow Containing Gyrotactic Microbes: A Bio-Microsystemtechnology and Bio-Fuel Cells Application

Scientists and researchers have been captivated by the field of nanotechnology research, drawn to its diverse applications such as cancer treatment, pharmaceuticals, aircraft manufacturing, nano-robot technology, bionano advancements, heat exchange instruments, engine coolant use, microelectronics, water distillation, pharmaceutical procedures, and rubber materials. Incorporating gyrotactic microbes into nanoparticles is crucial for enhancing the thermal efficiency of various systems, including microbial fuel cells, bacteria-powered micro-mixers, micro-volumes such as microfluidic devices, enzyme biosensors, and chip-shaped microdevices like bio-microsystems.This study focuses on investigating the bioconvectional flow of Casson nanofluid, incorporating nano-particles, gyrotactic micro-organisms, and thermal radiation, passing through a needle. The bioconvection fluid is formed through the combined effects of Lorentz forces, a magnetic field, and the interaction of motile micro-organisms with nanoparticles. The governing partial differential equations are transformed into ordinary differential equations using resemblance transformations, and the solution is obtained through the BVP4C solver shooting technique. The numerical results are presented using MATLAB, depicted in figures and tabular formats. The findings, interpreted from a physical standpoint, reveal that fluid flow decreases with an increase in bioconvection Rayleigh number and buoyancy ratio parameter. Thermal flow, on the other hand, increases with a rise in Brownian motion parameter and thermophoresis effect parameter. Concentration profiles decrease with an increase in thermophoresis parameter and Lewis number, while motile microorganism profiles decline with an augmentation in Peclet number and bioconvection Lewis number.

Two-temperature modeling of lamellar cathode arc

A three-dimensional, two-temperature (2T) model of a lamellar cathode arc is constructed, drawing upon the conservation equations for mass, momentum, electron energy, and heavy particle energy, in addition to Maxwell’s equations. The model aims to elucidate how the physical properties of electrons and heavy particles affect heat transfer and fluid flow in a lamellar cathode arc. This is achieved by solving and comparing the fields of electron temperature, heavy particle temperature, fluid flow, current density, and Lorentz force distribution under varying welding currents. The results show that the guiding effect of the lamellar cathode on current density, the inertial drag effect of moving arc, and the attraction effect of Lorentz force at the lamellar cathode tip primarily govern the distribution of the arc’s physical fields. The guiding effect localizes the current density to the front end of the lamellar cathode, particularly where the discharge gap is minimal. Both the inertial drag effect and the attraction effect of Lorentz force direct arc flow toward its periphery. Under the influence of the aforementioned factors, the physical fields of the lamellar cathode arc undergo expansion and shift counter to the arc’s direction of motion. A reduction in welding current substantially weakens the guiding effect, causing the arc’s physical fields to deviate further in the direction opposite to the arc motion. In comparison with a cylindrical cathode arc, the physical fields of the lamellar cathode arc are markedly expanded, leading to a reduction in current density, electron temperature, heavy particle temperature, cathode jet flow velocity, and Lorentz force.

Suction and Lorentz force effects on MHD free convective transport of micropolar fluid passing a Unsteady analysis

A comprehensive study of the nature of micropolar fluid on an unsteady MHD-free convective transference through a perforated sheet is discussed considering the suction and Lorentz’s force effects. The corresponding similarity equations of temperature, momentum, concentration, and angular momentum equations have been modified into the non-dimensional similarity equations of the temperature, momentum, concentration, and angular momentum equations by utilizing the similarity technique. The modified equations have been resolved by exerting the shooting technique with the help of the finite difference method (FDM) through MATLAB. The fluid flow is inversely proportional to the changes in micro rotational effect (Δ). The concentration boundary layer gets thinner as the Schmidt number (Sc) advances and hence the concentration of the fluid decreases. Micropolar fluid helps reduce drag forces and also acts as a coolant. The heat transmission rate advances by around 391%, and 110% due to growing amounts of Pr from 0.71 to 7.0, and v0 from 0.6 to 3.0, respectively. The surface couple stress decays by about 33%, 45%, and 36% due to increasing values of M from 0.6 to 3.6, ∆ from 3.0 to 6.0, and λ from 0.1 to 1.2, respectively.

Single-structure 3-axis Lorentz force magnetometer based on an AlN-on-Si MEMS resonator

This work presents a single-structure 3-axis Lorentz force magnetometer (LFM) based on an AlN-on-Si MEMS resonator. The operation of the proposed LFM relies on the flexible manipulation of applied excitation currents in different directions and frequencies, enabling the effective actuation of two mechanical vibration modes in a single device for magnetic field measurements in three axes. Specifically, the excited out-of-plane drum-like mode at 277 kHz is used for measuring the x- and y-axis magnetic fields, while the in-plane square-extensional mode at 5.4 MHz is used for measuring the z-axis magnetic field. The different configurations of applied excitation currents ensure good cross-interference immunity among the three axes. Compared to conventional capacitive LFMs, the proposed piezoelectric LFM utilizes strong electromechanical coupling from the AlN layer, which allows it to operate at ambient pressure with a high sensitivity. To understand and analyze the measured results, a novel equivalent circuit model for the proposed LFM is also reported in this work, which serves to separate the effect of Lorentz force from the unwanted capacitive feedthrough. The demonstrated 3-axis LFM exhibits measured magnetic responsivities of 1.74 ppm/mT, 1.83 ppm/mT and 6.75 ppm/mT in the x-, y- and z-axes, respectively, which are comparable to their capacitive counterparts.

Magnetoplasmonic Metasurface-Modulated Electrochemiluminescence Strategy for Extracellular Vesicle Detection.

Due to the ideal optical manipulation ability, the metasurface has broad prospects in the development of novel optical research. In particular, an active metasurface can control optical response through external stimulus, which has attracted great research interest. However, achieving effective modulation of the optical response is a significant challenge. In this work, we have developed a novel electrochemiluminescence (ECL) signal modulation strategy by an active magnetoplasmonic metasurface under an external magnetic field. The magnetoplasmonic metasurface was assembled based on yolk-shell Fe3O4@Au nanoparticles (Fe3O4@Au YS-NPs). On the one hand, the yolk-shell structure of Fe3O4@Au YS-NPs possessed the surface plasmon coupling effect and cavity-based Purcell effect, which provided high-intensity electromagnetic hot spots in the magnetoplasmonic metasurface. On the other hand, due to the strong magnetic response of the Fe3O4 core, the local magnetic field was induced by the external magnetic field, which further generated Lorentz force acting on the free electrons of Au nanoshells with strong optical anisotropy. The plasmon frequency of the metasurface can be effectively modulated by the Lorentz force effect. As a result, the ECL signal of nitrogen dots (N dots) was dynamically modulated and significantly enhanced at a specific polarization angle by the magnetoplasmonic metasurface under the variable external magnetic field. Based on the luminescence modulation ability and structure feature, the magnetoplasmonic metasurface was further established successfully as a sensing interface for gastric cancer (GC) extracellular vesicle (EV) detection. This study illustrated that the electromagnetic response of the active metasurface can effectively improve the optical modulation ability and luminescence sensing performance.

Effect of High-Frequency Electric Pulse on the Solidification Microstructure and Properties of Hypoeutectic Al-Si Alloy.

The effects of different pulse frequencies on the microstructure grain size and solid solubility of Al-9Si alloy were systematically investigated using OM, SEM, and EDS. The impact on the mechanical properties of the alloy was analyzed using a micro-Vickers hardness tester and multifunctional friction tester. During solidification, the Al-9Si alloy is exposed to high-frequency electric current pulses with a current density of 300 A/cm2 and frequencies of 0 Hz, 500 Hz, 1000 Hz, and 2000 Hz. The experimental results show that the Lorentz force also increases as the high-frequency pulse frequency increases. Intense electromagnetic stirring leads to grain refinement. However, as the pulse frequency continues to grow, the combined effect of Joule heating and Lorentz force results in an enlargement of the melt zone and an increase in grain size. At a pulse frequency of 1000 Hz, the eutectic structure size of the Al-9Si alloy is optimal, with the average size being reduced to 13.87 μm and a dense distribution, effectively eliminating primary Si. The EDS results revealed that the high-frequency pulse led to a more uniform distribution of Si elements within the matrix, and the solid solubility of Si in the α-Al matrix increased to a maximum value of 1.99%, representing a 39.2% increase. At a pulse frequency of 1000 Hz, the sample demonstrates the most favorable mechanical properties, with the friction coefficient reaching a minimum value of 0.302, representing a 37.7% decrease in the average friction coefficient. The results demonstrate that high-frequency pulsing is an effective method for enhancing the mechanical properties of Al-9Si alloy.

Numerical Investigation of the Magnetohydrodynamic Mixed Convection inside an Extended Curved Duct in the Presence of a Nanofluid of Different Metallic Oxides Nanoparticles

The numerical work presented in this paper focuses on the influence of the magnetic field and the nanoparticles metallic nature on the hydrodynamic and thermal behavior of a nanofluid flowing in an extended curved duct. It deals with a semi-toroidal curved duct with an expanded circular section. The narrowed part of this duct from which the nanofluid enters with a cold temperature, is considered to be thermally insulated. However, the extended part is kept at a constant hot temperature. The nanoparticles used in the present study respectively are Alumina (Al2O3), copper oxide (CuO) and iron trioxide (Fe3O4). In this study, the effects of inertia, buoyancy and Lorentz forces as well as the metallic nature of the nanoparticles suspended in the pure water have been highlighted on the thermal, hydrodynamic and economic levels. The study is based on the resolution of the classical monophasic equations governing the non-isothermal flow of nanofluids by the use of finite element method, namely: the mass, momentum and energy equations. The obtained results have shown that the buoyancy and inertia forces strongly favor the global heat exchange rate. Moreover, the magnetic force acts negatively on these thermal exchanges. Furthermore, the CuO nanoparticles have demonstrated a better heat transfer rate, approximately 7% higher than that of pure water. Nevertheless, according to the economic needs, we suggest we suggest using alumina nanoparticles, as their transfer rate is comparable to that of CuO nanoparticles. It should be noted, that this study provides important insights for many industrial applications where the curved ducts are strongly presented.

Effects of Suction and Lorentz Force on an Unsteady MHD Convective Mass and Heat Transfer Nanofluid Flow upon a Vertical Permeable Sheet

Effects of Suction and Lorentz Force on an Unsteady MHD Convective Mass and Heat Transfer Nanofluid Flow upon a Vertical Permeable Sheet

Convective heat transfer of electrically conducting MHD power law fluid through annular sector duct

This study deals with the effect of Lorentz force on forced convection flow of electrically conducting magneto-hydrodynamic, (MHD) power law fluid through the annular sector duct by using finite volume method. In existence literature, hydro-thermal flow of MHD power law fluid within an annular sector duct has not been reported. The effect of Lorentz force on hydro-thermal power law fluid flow makes it very much novel in its own right. Here the main objective is to explore the effect of Lorentz force on hydro-thermal flow characteristics. The influence of uniform magnetic field is taken parallel to the radial direction. The effects of Hartman parameter, [Formula: see text] and power law index, [Formula: see text], corresponding to Lorentz force and power law fluid respectively, on the quantities of interest such as velocity and temperature profiles, friction factor and average Nusselt number [Formula: see text] are discussed for different geometric configuration parameters’ values of the annular sector duct. Computer code is developed and validated by comparing the results of limiting cases with the available literature. It has been observed that [Formula: see text] increases with the increase in [Formula: see text]. This trend is prevalent in both pseudo-plastic and dilatant fluids. The impact of [Formula: see text] is pronounced in the later case.

Comparative numerical analysis of electromagnetic forces in DC and HFPC TIG welding

The paper presents a detailed theoretical analysis of the electromagnetic forces in the arc plasma and the weld pool metal in Tungsten Inert Gas (TIG) welding at direct current (DC) and high-frequency pulse current (HFPC) modulation with a frequency of 10 kHz. The electromagnetic (Lorentz) force, acting on arc plasma and metal is presented via potential (magnetic pressure) and rotational (equivalent electromagnetic force) force components. This approach allows us to substantially simplify the analysis of the Lorentz force effect on the arc plasma and weld pool metal under different arc burning modes. It was shown that in HFPC TIG welding with a given frequency, the effect of modulated current on the arc plasma is inherently non-stationary, whereas the effect on the weld pool metal is determined by the time-averaged magnitude of electromagnetic force throughout the period of current modulation. The proposed approach serves as a basis for numerical analysis of the electromagnetic forces in arc plasma and weld pool metal during DC and HFPC modes of the welding process. We established that the application of HFPC modulation promotes a greater intensity of both the gas-dynamic processes in the welding arc, thereby significantly increasing the pressure on the weld pool surface, and convective heat transfer from the most heated central region near the weld pool surface towards the weld pool bottom. Both these factors lead to an increase of the arc penetrability in the case of the HFPC mode compared with the DC mode, all other conditions being equal.