External Magnetic Field Source Research Articles

Further insights into steady three-dimensional MHD Sakiadis flows of radiating-reacting viscoelastic nanofluids via Wakif’s-Buongiorno and Maxwell’s models

AbstractKeeping in mind the stress relaxation tendency of many viscoelastic multi-phase flows (e.g., polymer solution flows and transport phenomena of red cell suspensions within blood media), the present research investigation intends principally to develop a realistic model for revealing properly the aspects of reacting-radiating Maxwell nanofluids during their laminar boundary layer flows in the steady regime over a horizontal impermeable surface under a transversal magnetic influence. For this purpose, the principal leading differential formulation is derived theoretically by linking Wakif’s-Buongiorno approach with Maxwell’s model. By invoking fundamentally the general boundary layer assumptions and the passive control strategy for the nanoparticles, the governing PDEs’ formulation is simplified accordingly and then stated properly for the case of the convective heating condition at the impermeable bi-stretching surface. By executing a feasible non-dimensionalization technique, the monitoring ODEs’ system is achieved successfully, whose solutions are presented precisely in different illustrative scenarios using Richardson’s extrapolation method. After carrying out successfully several validating tests, it is demonstrated that the weakly viscoelastic feature has generally a slight delaying effect on the nanofluid motion. This dynamical weakening can be reinforced more with the generation of thermal energy by intensifying the external magnetic field source. Additionally, these physical factors show an intensifying influence on the surface drag forces. However, a dropping impression is seen for the local heat transfer at the contact surface. Contrary to the broadening impact of the radiative heat transfer as well as the convective heating and thermophoresis mechanisms on the thermal and mass boundary layer regions, it is witnessed that the first-order chemical reaction mechanism and Brownian’s motion exhibit a shrinking impact on the mass boundary layer region.

Magnetohydrodynamic and Ferrohydrodynamic Fluid Flow Using the Finite Volume Method

Many problems in fluid mechanics describe the change in the flow under the effect of electromagnetic forces. The present study explores the behaviour of an electric conducting, Newtonian fluid flow applying the magnetohydrodynamics (MHD) and ferrohydrodynamics (FHD) principles. The physical problems for such flows are formulated by the Navier–Stokes equations with the conservation of mass and energy equations, which constitute a coupled non-linear system of partial differential equations subject to analogous boundary conditions. The numerical solution of such physical problems is not a trivial task due to the electromagnetic forces which may cause severe disturbances in the flow field. In the present study, a numerical algorithm based on a finite volume method is developed for the solution of such problems. The basic characteristics of the method are, the set of equations is solved using a simultaneous direct approach, the discretization is achieved using the finite volume method, and the solution is attained solving an implicit non-linear system of algebraic equations with intense source terms created by the non-uniform magnetic field. For the validation of the overall algorithm, comparisons are made with previously published results concerning MHD and FHD flows. The advantages of the proposed methodology are that it is direct and the governing equations are not manipulated like other methods such as the stream function vorticity formulation. Moreover, it is relatively easily extended for the study of three-dimensional problems. This study examines the Hartmann flow and the fluid flow with FHD principles, that formulate MHD and FHD flows, respectively. The major component of the Hartmann flow is the Hartmann number, which increases in value the stronger the Lorentz forces are, thus the fluid decelerates. In the case of FHD fluid flow, the major finding is the creation of vortices close to the external magnetic field source, and the stronger the magnetic field of the source, the larger the vortices are.

Substrates with Different Magnetic Properties Versus Iron-Nickel Film Electrodeposition

Abstract The hereby work presents the iron-nickel alloys electroplated on the different metallic substrates (aluminium, silver, brass) using galvanostatic deposition, with and without presence of the external magnetic field (EMF). The films were obtained in the same electrochemical bath composition - mixture of iron and nickel sulphates (without presence of additives) in the molar ratio of 2 : 1 (Ni : Fe), the electric current density (50.0 mA/cm2), and the time (3600 s). The mutual alignment of the electric (E) and magnetic field (B) was changeable - parallel and perpendicular. The source of EMF was a set of two permanent magnets (magnetic field strength ranged from 80 mT to 400 mT). It was analysed the surface microstructure, composition, morphology, thickness and the mechanical properties (roughness, work of adhesion). The surface morphology and the thickness of films were observed by Scanning Electron Microscopy (SEM) and Confocal Laser Scanning Microscopy (CLSM). The elemental composition of all FeNi films was measured using Wavelength Dispersive X-Ray Fluorescence (WDXRF). The crystalographic analysis of the deposits was carried out by X-Ray Diffraction. Depending on the used substrate, modified external magnetic field orientation influenced the tribological and physio-chemical properties of the deposited layers. The diamagnetic substrates and EMF application reduced the FeNi thickness and the average crystallites size, in contrast to the paramagnetic substrate. Parallel EMF increased the value of the tribological parameters for CuZn and Ag but decreased for Al. The content of FeNi structure was rising in the case of diamagnetic substrate and the dependence was opposite on the paramagnetic substrate.

Simulation of the magnetic field in residential buildings with built-in substations based on a two-phase multi-dipole model of a three-phase current conductor

Problem. Substations 10(6)/0.4 kV built into residential buildings create a magnetic field with magnetic flux density of more than 10 μT in nearby residential premises, which is a danger to the health of the population and makes the study of this magnetic field relevant for the development of methods for its protection. The main source of the substations external magnetic field is their low-voltage current conductor, the contribution of which to the total level of the magnetic field is more than 90 %. Multi-dipole mathematical models, which have a clear physical interpretation, are a promising method of modeling the substations magnetic field, which is important for the further development of methods of population protection. The purpose of the work is to modify the well-known multi-dipole model for calculation based on it with a limited error of the external magnetic field of current conductors of built-in substations that are close to residential buildings at a distance of up to one meter. Methodology. A modified two-phase multi-dipole mathematical model of the main source of the external magnetic field of substation – its three-phase low-voltage current conductors – is proposed, which, unlike the existing model, is based on a two- you to halve the distance to the area of calculation without increasing the error. Verification. An experimental verification of the modified two-phase multi-dipole model of the magnetic field of a three-phase 100 kVA transformer substation on its full-scale physical model was carried out, and the results of the experiment were presented, confirming the coincidence of the calculation and the experiment with a spread of no more than 7 %.

Effect of Magnetic Shielding on Levitation Characteristics of Superconducting Gravimeter

The superconducting gravimeter is currently the most accurate instrument in relative gravity measurement, so the high-precision calculation and analysis of superconducting magnetic levitation system is crucial to the development work of superconducting gravimeter. Shielding material can weaken the influence of external magnetic field source fluctuation on the internal levitation magnetic field and provide a stable electromagnetic environment for the magnetic levitation system. But at the same time, shielding material will also have an impact on the internal suspended magnetic field itself, which will lead to large deviations in the study of electromagnetic characteristics of the magnetic levitation system. This article establishes and optimizes the simulation calculation model of a superconducting gravimeter magnetic levitation system based on <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> method, and studies the effect of magnetic shielding on the magnetic field, levitation force, and magnetic force gradient of the internal levitation system. After that, the simulation calculation results are compared with the experimental results, and the simulation calculation error of superconducting levitation force and magnetic gradient is less than 1%, which verifies the correctness of the optimized simulation model. This study is an important guide for the accurate calculation of the electromagnetic properties of all superconducting systems containing magnetic shielding materials, such as superconducting gravimeter, superconducting gravity gradiometer, etc.

Entropy analysis for MHD blood flow of hybrid nanoparticles (Au–Al 2 O 3 /blood) of different shapes through an irregular stenosed permeable walled artery under periodic body acceleration: Hemodynamical applications

The current study investigates the entropy generation for hybrid nanoparticles (Au–Al2O3/blood) through a vertical irregular stenosed artery in the presence of an external magnetic field, Joule heating, viscous dissipation, and heat source considering two-dimensional pulsatile blood flow and periodic body acceleration. The blood flow is assumed to be unsteady, laminar, viscous, and incompressible, and the artery walls are considered as permeable. The Reynolds temperature-dependent viscosity model is used to determine the variable viscosity effects. The governing momentum and energy equations are solved using Crank–Nicolson finite difference method by employing an appropriate coordinate transformation to build an accurate mesh using rectangular mesh units. Outcomes of the work are represented graphically for velocity, wall shear stress (WSS), volumetric flow rate, resistance impedance, temperature, heat transfer coefficient, entropy generation, and Bejan number, respectively. Also, the results are validated for velocity and temperature profiles for a given set of values of the dimensionless parameters. The entropy generation increases with rising values of shape parameter (n) up to a specific radius ( x 1 ∗ = 0.84 $x_1^*=0.84$ ) and then changes its behavior in the vicinity of the stenotic zone, in which entropy generation decreases with increasing values of shape parameter (n). The current findings may be helpful for biomedical scientists those are interested to investigate the treatment of various cardiovascular diseases (CVDs).

The Influence of Magnetic Composite Capsule Structure and Size on Their Trapping Efficiency in the Flow.

A promising approach to targeted drug delivery is the remote control of magnetically sensitive objects using an external magnetic field source. This method can assist in the accumulation of magnetic carriers in the affected area for local drug delivery, thus providing magnetic nanoparticles for MRI contrast and magnetic hyperthermia, as well as the magnetic separation of objects of interest from the bloodstream and liquid biopsy samples. The possibility of magnetic objects’ capture in the flow is determined by the ratio of the magnetic field strength and the force of viscous resistance. Thus, the capturing ability is limited by the objects’ magnetic properties, size, and flow rate. Despite the importance of a thorough investigation of this process to prove the concept of magnetically controlled drug delivery, it has not been sufficiently investigated. Here, we studied the efficiency of polyelectrolyte capsules’ capture by the external magnetic field source depending on their size, the magnetic nanoparticle payload, and the suspension’s flow rate. Additionally, we estimated the possibility of magnetically trapping cells containing magnetic capsules in flow and evaluated cells’ membrane integrity after that. These results are required to prove the possibility of the magnetically controlled delivery of the encapsulated medicine to the affected area with its subsequent retention, as well as the capability to capture magnetically labeled cells in flow.

Modeling and simulation of smart magnetic self-assembled nanomicelle trajectories in an internal thoracic artery flow for breast cancer therapy.

Magnetic drug targeting (MDT) is one of the most modern techniques in cancer therapy for its ability to reduce the side effects of chemotherapy experienced by systemic drug administration. In this study, a comprehensive mathematical model has been developed to predict the drug particle trajectories of anticancer dasatinib magnetic nanomicelles (DAS-MNM) released in an internal thoracic artery (ITA) blood flow for breast cancer therapy using an external magnetic field. Several factors are investigated in regard to the efficiency of MDT through the ITA, including magnetic field strength (MFS), relative magnetic permeability, magnet size, drug particle size, and initial position of drug particle. The drug particle trajectory results confirmed the successful MDT using an external magnetic field with a capture efficiency of more than 90%. This was achieved by employing a wide range of particle sizes of DAS-MNM close to the external magnetic field source at the arterial wall than in other positions. Moreover, the results showed that the number of trapped particles increased with increasing both MFS and drug particle diameter within the target tissue, while the drug particle permeability did not have a considerable effect on the particle retention. In addition, for achieving a successful drug/cargo delivery through the arteries, the magnetic field, the particle size, and the initial release locations should be adjusted simultaneously. The present work offers insights into the critical factors in MDT with a significant impact on breast cancer therapy, tissue engineering, and regenerative medicine. Magnetic drug targeting model of anticancer dasatinib magnetic nanomicelles (DAS-MNM) released in an internal thoracic artery blood flow for breast cancer therapy.

Buried Magnetic Material Detection System: An SVM Algorithm Application

In recent times, studies about remote-sensing methods have focused on improving variables like sensing distance, sensitivity, and power consumption of available remote-sensing methods. The main target of this study is to improve these variables for the magnetic anomaly detection (MAD) method, in addition to determining upper surface geometry of the sheath with the support vector machine (SVM) algorithm to allow detection of buried ferromagnetic-sheathed explosives, minimize the number of false alarms, and thus shorten the scanning time. The classification process with the SVM algorithm separates this study from others. In line with this, instead of an external magnetic field source, in this study, the Earth's magnetic field was used with a TE100 fluxgate sensor, which has very low power consumption, used as a magnetic sensor to develop a highly sensitive new magnetic measurement and detection system. The system identifies anomalies in the vertical component of the Earth's magnetic field due to the magnetic characteristics of the buried sample in order to determine both the coordinates of the buried object within the scanning field and the upper surface geometry. The system is formed using a five-axis movement CNC platform including sensors and camera. Software was developed using python programming language with a QT graphical user interface (GUI) in order to control the CNC platform, take photographs of the soil, and process sensor data to ensure identification of the upper surface shape of the object under the soil. After obtaining all data for a 30×30 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> scanning area, the software colors the data from blue to red and visualizes this transparently above a photograph of the soil on the monitor. After this stage, a model is created using thresholding, selective search algorithm, and SVM in order to identify the location and upper surface shape of the sample located within the measurement region. Tests performed after SVM training determined the system can classify the upper surface geometry of buried samples with 88% success.

A numerical study of the entropy generation and heat transfer rate of airflow around a NACA 0015 airfoil subjected to an external magnetic field

In the present study, the thermal Lattice Boltzmann Technique is combined with the Ghost Fluid method to simulate the flow and heat transfer rate around a NACA 0015 airfoil in the presence of an external magnetic field source. It is tried to investigate the mutual effects of the Hartmann and Reynolds numbers as well as the magnetic field angle and the attack angle of the airfoil on the flow and heat transfer characteristics. Besides, the total entropy generation rate of the system was studied through its main components, i.e. entropy generation rate due to friction, heat transfer, and Magneto Hydrodynamics. Therefore, the tests were carried out for various Re and Ha numbers, plus different magnetic field angles and airfoil attack angles, and their influence on the active parameters which are Cd, Cl, and Nu, along with the entropy generation rate of the system, were recorded. The results revealed that with an increment of the Re number the Cd and Cl graphs drop, but the Nu value raises. Also, the total entropy generation rate of the system is at its maximum around γ = 60.

Energy harvesting applications using 3D-printed coreless generator

3D-printed coreless generator has been presented for energy harvesting applications using permanent magnet as source of external magnetic field in the rotor. The phototype of proposed coreless generator is built using 3D-printer with Black Polylactic Acid (PLA) as a filament for stator housing, rotor and other parts. The major parts of the proposed coreless generator are the stator, which has four coils of winding copper wire and the rotor with eight permanent magnets which are arranging N and S magnet poles alternately. This research is conducted to determine how much power can be generated from the proposed 3D-printed permanent magnet generator. The prototype permanent magnet generator is tested with rotational speed and load condition. The experimental results have been shown that the coreless generator can generate the electrical energy up to 5 W at 6000 rpm.

Effect of number of permanent magnetic poles on 3D printed coreless generator rotor

3D-printed coreless generator using rotors with 4 poles permanent magnet and 8 poles permanent magnet as source of external magnetic field has been presented for energy harvesting applications. The prototype of proposed coreless generator is built using 3D-printer with Black Polylactic Acid (PLA) as a filament for stator housing, rotor and other parts. The major parts of the proposed coreless generator are the stator, which has four coils of winding copper wire and two rotors with four permanent magnet and eight permanent magnets which are arranging N and S magnet poles alternately. The prototype permanent magnet generator is tested with rotational speed and load condition. The experimental results have been shown that the coreless generator can generate It was found that 3D-printed coreless generator can generate electric energy up to 10300 mW for rotor with eight permanent magnets and 9000 mW for rotor with four permanent magnet at 5000 rpm, respectively.

Design and experimental evaluation of a linear thermomagnetic motor using gadolinium: Preliminary results

Thermomagnetic motors are based on the effect of heat on the magnetic properties of ferromagnetic materials around their magnetic phase transition (Curie) temperature. The main components of these motors are the magnetic material and the magnetic circuit. Changing the magnetic ordering by heating or cooling the magnetic material it is possible to generate power when the magnetic material interacts with an external magnetic field source. If the magnetic material temperature transition is around room temperature, it may have potential to be applied in thermomagnetic motors using low-grade thermal waste as heat source. In this way, the present work proposes a novel concept of a linear thermomagnetic motor using a double-C shape permanent magnet magnetic circuit to convert thermal energy into mechanical energy. The double-C magnetic circuit has two high field regions able to host, at least, two magnetic material heat exchangers connected to each other, but operating in opposite magnetic phases: if the first material heat exchanger is at a non-magnetic phase, the second is ferromagnetic. Thus, when the force equilibrium of such configuration is not satisfied, a linear motion is created. An experimental apparatus of the proposed concept was designed and built. Gadolinium spheres were used as magnetic material. Experimental tests for static forces and generated power were performed. Preliminary results presented a maximum generated power of 0.41 W at an operating frequency of 0.5 Hz.

Effects of the Applied Magnetic Field on the Quality of Resistance Spot Welding in Rail Vehicles Using Stainless-Steel

The ring magnet nested on the surface of a spot welding electrode is used as the external magnetic field source. We analyzed the effects of an applied magnetic field on the appearance quality of joints, the nugget diameter of resistance spot welding for rail vehicles using stainless steel through comparative resistance spot welding experiments. A coupled electrical-magnetic finite element model was established to analyze the effect of magnetic forces on the welding current direction. Result show that the appearance of a magnetically assisted spot welding joint was significantly better than that obtained by conventional spot welding. The nugget diameter of the welding spot was also significantly increased. The Lorentz force introduced by applied magnetic field deflects the path of electrons in welding electoral field, which makes nuggets with a larger radius and a lower depth.

Modelling of magnetic bead transport in a microvascular network

In in vivo applications of magnetic particles one crucial aspect is the control of their transport in the tissue microvasculature and their release to target areas. These mechanisms can be driven and influenced by external magnetic fields with large gradients. Experimental results can be elucidated with the aid of in silico models that can also be employed to design optimized multifunctional particles and magnetic field sources. In this framework, we have developed a numerical model that enables us to calculate the trajectory of an ensemble of magnetic nano/microbeads injected in a blood vessel and manipulated by an applied magnetic field. The model combines Navier-Stokes equations for the fluid dynamics simulation of blood flow with classical Newtonian mechanics for bead motion, performing the analysis in a 3D vessel segment reconstructed from a computed tomography scan. The numerical model is applied to study the influence of bead properties (size and magnetic moment) on both transport and adhesion rate, taking into account the interplay of magnetic and viscous drag forces, as well as magnetic dipole–dipole and steric interactions. We also consider different configurations of the external magnetic field source, in order to optimize bead accumulation and adhesion to the vessel wall in a specific target region, processes that can be driven by magnetic forces.

An Improved Surface Charge Model for the Static Force Calculation Among the Permanent Magnets in Magnetic Bearings or Magnetic Springs

This article presents an improved surface charge model for the static force calculation among the permanent magnets (PMs). Generally, there is an error source of the classical surface magnetic charge model due to the assumption of the unit relative permeability. This error source can be ignored for the ferromagnetic actuators but will bring a significant deviation to the ironless devices, such as the magnetic bearings or magnetic springs. To calculate the static force among the PMs more accurately, the estimation for the actual working point of each PM is required. The magnetic field iteration method is used in this article, in which the inner magnetic field intensity of one PM is decided by itself and the external magnetic field sources. By dividing one cuboid magnet into amounts of small cubes, the integral operation can be simplified into the numerical superposition when calculating the average working point. The influences of the number of nodes and iteration times on the model accuracy are analyzed. Finally, two magnetic springs are manufactured and well tested. The static force calculation is based on the expressions of Yonnet and the improved surface charge model. Compared with the classical model, the model error of the improved model can be reduced and the static force values are closer to the 3-D finite-element method (FEM) and experiment results. Furthermore, the improved model has remarkable advantage over the 3-D FEM in aspect of computation time, which is suitable for the design and analysis of the magnetic bearing or magnetic springs.

Incompressible smoothed particle hydrodynamics method for natural convection of a ferrofluid in a partially layered porous cavity containing a sinusoidal wave rod under the effect of a variable magnetic field

Abstract

Numerical simulation of Al2O3-water nanofluid heat transfer and entropy generation in a cavity using a novel TVD hybrid LB method under the influence of an external magnetic field source

In the present study, a novel TVD Hybrid FD-LBM technique is developed to simulate Al2O3-Water nanofluid flow under Buongiorno assumptions. It goes without saying that all explicit numerical schemes suffer from serious stability problems when dealing with low dissipation equations. The simple Single Relaxation Time Lattice Boltzmann method also is not an exception to this rule; that’s why some modern LBM techniques such as Multi Relaxation Time methods are developing day to day. These new techniques add artificial dissipation to the system to keep the oscillating errors of the convective fluxes damped and consequently the numerical procedure stability rises. In this paper, a novel TVD hybrid technique is applied to the Buongiorno model which has relatively low diffusive fluxes in the concentration equation and the flow, heat transfer, and concentration equations are solved in a closed cavity with an elliptic obstacle. Moreover, the influence of an external magnetic field source on the flow and heat transfer rate is studied and the entropy generation of the whole system is investigated. The results revealed that there is a maximum circulation angle for each Ha number which provides relatively higher Nusselt and Sherwood numbers. At these magnetic field angles, Bejan number decreases but they will not necessarily represent the maximum entropy generation points of the system.

Improving weld penetration by employing of magnetic poles’ configurations to an autogenous tungsten inert gas (TIG) welding

A new configuration of permanent magnet as a source of external magnetic field has been established to an autogenous tungsten inert gas (TIG) welding. The external magnetic field is generated by rectangle shape NdFeB permanent magnets of 260 mT and arranged in cups-type magnetic field (CMF). A charge-coupled device (CCD) is applied to monitor the phenomenon of the arc shape. The material used in this experiment is SS304 with a thickness of 2 mm. This study aims at investigating the effect of external magnetic field towards the arc shape and finding the configuration, which can reduce the power consumption and improve penetration. A significant effect on the improvement of welding efficiency can be achieved by using PR-NNSS-SD (50 or 70 mm), PP-NNSS-SD (70 or 90 mm), or PP-NSNS-Pull (50 mm). These configurations can reduce the power consumption up to 11%.

Magnetic Field-Assisted Radiation Enhancement From a Large Aperture Photoconductive Antenna

The generation of terahertz radiation using photoconductive antennas is becoming very popular. Several experimental and simulation studies have been performed to study the characteristics of the photoconductive antenna (PCA). Although various methods have been proposed to increase the radiated power from it, the radiated power remains very low. In this paper, we present an analytical study of improving the radiated power from a large aperture PCA using an external magnetic field source. The transit time behavior of the carriers is computed using the basic semiconductor carrier dynamics model, including the transient mobilities with the dependencies on the electric field and carrier’s concentration. Analytical studies show that substantial enhancement in the radiated field can be achieved when such external magnetic field is applied. Furthermore, the polarity of the radiated field depends on the orientation of the applied magnetic field. The results obtained from analytical calculations exhibit similar behavior as reported in some experimental results.