Modelling of Electrode Size Influence on Electrochemical MHD Processes

2021 ◽  
Vol 105 (1) ◽  
pp. 509-516
Author(s):  
Martin Mačák ◽  
Petr Vyroubal
Keyword(s):  
Magnetic Field ◽  
Electrochemical Reaction ◽  
Microfluidic Devices ◽  
Ansys Fluent ◽  
Electrode Size ◽  
Scan Rate ◽  
Current Densities ◽  
Control Fluid ◽  
The Magnetic Field ◽  
Mixing And Transport

The presented article describes a simulation of an electrochemical reaction in a presence of a magnetic field using a custom model implemented into Ansys Fluent. The influence of electrode size and the effect of scan rate is investigated further. The results show that the magnetic field can significantly increase mixing and transport of species towards the electrode, which results in higher obtained current densities. Additionally, this method can be used to control fluid flow in microfluidic devices.

The Function of Magnetic Field in a Magnetic-Electrochemical Compound Polishing

2010 ◽  
Vol 97-101 ◽  
pp. 4141-4145 ◽  
Author(s):  
Li Min Shi ◽  
Er Liang Liu ◽  
Yong Jiang Niu ◽  
Yu Quan Chen
Keyword(s):  
Magnetic Field ◽  
Mathematical Model ◽  
Concentration Polarization ◽  
Electrochemical Reaction ◽  
Charged Particles ◽  
Polishing Process ◽  
Electrical Field ◽  
Movement Model ◽  
The Mathematical Model ◽  
The Magnetic Field

Traditionally, the magnetic field is always vertical to the electrical field in a magnetic-electrochemical compound polishing.The magnetic field is set to parallel the electrical field in this paper. The mathematical model of the charged particles movement in a magnetic field is established through the analysis of its movement process when using Coulomb laws and Lorentz force. Through constructing the velocity formulation and loci formulation, the function of the magnetic field is proved. Because of the magnetic field, the concentration polarization of electrochemical reaction can be reduced more and the electrochemical reaction can be accelerated easily than the traditional polishing in which the magnetic field is vertical to the electrical field. Finally, to verify the model, the magnetic-electrochemical compound polishing process has been tested and the results, compared with those obtained from the model, have shown the movement model is reasonable and the analysis to function of magnetic field is correct.

Galvanomagnetische, thermoelektrische und thermomagnetische Eigenschaften von Wismut-Tellurid für beliebige Magnetfelder

1967 ◽  
Vol 22 (12) ◽  
pp. 2086-2096
Author(s):  
Udo Hübner
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Its Region ◽  
Energy Current ◽  
Starting Point ◽  
Mass Tensor ◽  
Current Densities ◽  
Peltier Coefficient ◽  
Scattering Time ◽  
The Magnetic Field

The four matrices of the electrical and the energy current densities are derived for bismuth-Telluride in arbitrary magnetic fields on the basis of DRABBLE'S six-ellipsoid-model. The scattering time will be taken anisotropic but not necessarily diagonal in the same system as the mass tensor. The starting point is BOLTZMANN'S transport equation in its region of validity. These four matrices are converted to resistance, absolute thermopower, PELTIER coefficient and electronic part of the heat conductivity for vanishing magnetic field and for magnetic fields parallel to the trigonal and the binary axis of the crystal. Saturation formulas for all directions of the magnetic field are deduced. Four resistance components mesured in dependence of the magnitude of the magnetic field are used to evaluate the band parameters which are different once more from data of DRABBLE and TESTARDI; but they are independent of the magnitude of the magnetic field within the limit of error.

scholarly journals Ionospheric currents estimated simultaneously from CHAMP satelliteand IMAGE ground-based magnetic field measurements: a statisticalstudy at auroral latitudes

2004 ◽  
Vol 22 (2) ◽  
pp. 417-430 ◽  
Author(s):  
P. Ritter ◽  
H. Lühr ◽  
A. Viljanen ◽  
O. Amm ◽  
A. Pulkkinen ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Local Time ◽  
Hall Current ◽  
Activity Index ◽  
Current System ◽  
Current Model ◽  
Field Measurements ◽  
Magnetic Field Measurements ◽  
Current Densities ◽  
The Magnetic Field

Abstract. One important contribution to the magnetic field measured at satellite altitude and at ground level comes from the external currents. We used the total field data sampled by the Overhauser Magnetometer on CHAMP and the horizontal magnetic field measurements of the IMAGE ground-based magnetometer network to study the ionospheric Hall current system in the auroral regions. For the CHAMP data a current model consisting of a series of lines and placed at a height of 110km is fitted to the magnetic field signature sampled on the passage across the polar region. The derived current distributions depend, among others, on season and on the local time of the satellite track. At dawn/dusk the auroral electrojets can be detected most clearly in the auroral regions. Their intensity and location are evidently correlated with the A E activity index. For a period of almost two years the results obtained from space and the currents determined from ground-based observations are studied. For the full IMAGE station array a newly-developed method of spherical elementary current systems (SECS) is employed to compute the 2-D equivalent current distribution, which gives a detailed picture of an area covering latitudes 60° – 80° N and 10° – 30° E in the auroral region. Generally, the current estimates from satellite and ground are in good agreement. The results of this survey clearly show the average dependence of the auroral electrojet on season and local time. This is particularly true during periods of increased auroral activity. The correlation coefficient of the results is close to one in the region of sizeable ionospheric current densities. Also the ratio of the current densities, as determined from above and below the ionosphere, is close to unity. It is the first time that the method of Hall current estimate from a satellite has been validated quantitatively by ground-based observations. Among others, this result is of interest for magnetic main field modelling, since it demonstrates that ground-based observations can be used to predict electrojet signatures in satellite magnetic field scalar data. Key words. Ionosphere (auroral Ionosphere; electric fields and currents; ionosphere-magnetosphere interactions)

scholarly journals Continuum sensitivity and design optimization of superconducting systems under critical current densities with magnetic field dependence

2021 ◽  
Author(s):  
Kyungsik Seo ◽  
Tim Coombs ◽  
Il Han Park
Keyword(s):  
Magnetic Field ◽  
Design Optimization ◽  
Critical Current ◽  
Current Density ◽  
State Equation ◽  
Design Sensitivity ◽  
Continuum Sensitivity ◽  
Current Densities ◽  
The Magnetic Field ◽  
The Continuum

AbstractThis paper presents an approach for deriving the continuum sensitivity of superconducting systems operating at critical current densities and an optimization method based on the continuum sensitivity. In the sensitivity problem, the superconducting systems is represented by a variational state equation, wherein the magnetic permeability depends on the magnetic field, which is transformed from a state equation with a field-dependent source. The design sensitivity is derived using the material derivative concept of continuum mechanics and the adjoint variable method. The adjoint system has a material property represented as a symmetric tensor that contains the sensitivity of the current density with respect to the magnetic field. The design sensitivity is represented in the analytical form of a surface integral on the interface between the superconducting material and its surroundings, which depends on the sensitivity of the current density. The optimization scheme is constructed based on the continuum design sensitivity. In the design optimization, the level set method is used to express the shape variation of the superconducting materials. The numerical example of infinite solenoids demonstrates that the design sensitivity provides an accurate design solution considering the critical current condition. In addition, the design example of a magnetic resonance imaging solenoid shows that the derived design sensitivity has the inherent ability for attaining the compact design by treating the input current of a superconducting system as a critical condition.

scholarly journals Euler potentials for two layers with non-constant current densities in the ambient magnetic field aligned to the layers

2016 ◽  
Vol 34 (12) ◽  
pp. 1165-1173
Author(s):  
Marek Vandas ◽  
Eugene P. Romashets
Keyword(s):  
Magnetic Field ◽  
Current Density ◽  
Previous Treatment ◽  
Homogeneous Magnetic Field ◽  
Constant Current ◽  
Constant Current Density ◽  
New Approach ◽  
Current Densities ◽  
The Magnetic Field ◽  
Birkeland Currents

Abstract. The Euler potentials for two current layers aligned to an ambient homogeneous magnetic field are found. Previous treatment of such a system assumed constant current density in the layers. However, the magnetic field becomes infinite at the edges. The new approach eliminates this inconsistency by introducing an inhomogeneous current density. Euler potentials are constructed semi-analytically for such a system. Charged-particle motion and trapping in it are examined by this representation. Using Euler potentials, the influence of current sheets of zero and non-zero thicknesses on energetic-particle fluxes is investigated, and characteristic flux variations near the sheets are presented. The results can be applied to Birkeland currents.

scholarly journals A Novel Augmented Railgun Using Permanent Magnets

2019 ◽  
Vol 8 (1) ◽  
pp. 99-105
Author(s):  
M. B. Heydari ◽  
M. Asgari ◽  
L. Gharib ◽  
A. Keshtkar ◽  
N. Jafari ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Permanent Magnet ◽  
Lorentz Force ◽  
Permanent Magnets ◽  
Pulse Current ◽  
Current Source ◽  
The Finite Element Method ◽  
Current Densities ◽  
Constant External Magnetic Field ◽  
The Magnetic Field

A novel augmented railgun using a permanent magnet is proposed in this paper. The effects of the permanent magnet on the magnetic field and distribution of current density have been investigated. High current densities in the railguns can lead to high local temperature and erosion of the rails. Therefore, the current densities in the rails and armature should be decreased without the reduction of the Lorentz force which is required for acceleration. For this purpose, augmentation of the magnetic field can be used as an effective method. The Finite Element Method (FEM) simulations have been applied in this article to analyze the performance of the railgun in the presence of the magnets. Two augmented railgun structures have been introduced to produce a constant external magnetic field. For both structures, augmented railgun characteristics are studied in comparison to the railgun without the augmentation. The results show that augmentation with permanent magnet increases railgun efficiency, especially in low current railguns. For pulse current source I=30kA, Lorentz force of the augmented railgun with four magnets is 2.02 times greater than the conventional railgun.

Numerical Analysis of Magnetic Field and Heat Transfer of a Reciprocating Magnetocaloric Regenerator Using a Halbach Magnet Array

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
Tunahan Akış ◽  
Abdullatif Hamad ◽  
Mehmet Akif Ezan ◽  
Erim Yanık ◽  
Ahmet Yılancı ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Pressure Difference ◽  
Thermal Analyses ◽  
Temperature Drop ◽  
Reynolds Numbers ◽  
Heat Transfer Fluid ◽  
Ansys Fluent ◽  
Fluent Software ◽  
The Magnetic Field

Abstract In this study, a numerical model of a reciprocating magnetocaloric regenerator using a Halbach magnet array is developed in ansys-fluent software. The model consists of three components, namely, (i) the Halbach magnet array, (ii) the magnetocaloric material (MCM), and (iii) the heat transfer fluid. A two-dimensional (2D) domain is studied due to the axisymmetric geometry of the physical model. A pressure difference is defined between the inlet and outlet sections of the fluid domain to maintain a reciprocating fluid flow. In the proposed computational scheme, a segregated approach is followed to consider the spatial distribution of the magnetic field in the thermal analyses. Therefore, a 2D magnetic field within the MCM is computed using an analytical approach at first, and its results are integrated into ansys-fluent with a user-defined function (UDF). Hydrodynamic and heat transfer characteristics of the proposed regenerator model are evaluated under various Reynolds numbers and cycle durations. Moreover, the temperature drop at the cold side of the regenerator is represented in terms of the pressure difference, flow duration, and the diameter of Gadolinium (Gd) as the MCM. For the current geometrical configurations, it is observed that the magnetic field varies from 0.4 T to 1 T within Gd. The highest temperature spans are measured as 8.4 K, 7.5 K, and 7.2 K numerically for the cycle durations of 1.2 s, 2.2 s, and 4.2 s, respectively.

scholarly journals The three-dimensional structure of the magnetic field of a sunspot

2008 ◽  
Vol 4 (S259) ◽  
pp. 225-226
Author(s):  
Horst Balthasar ◽  
Peter Gömöry
Keyword(s):  
Magnetic Field ◽  
Spatial Resolution ◽  
Near Infrared ◽  
Field Vector ◽  
Spectral Lines ◽  
Dimensional Structure ◽  
Diagnostic Tools ◽  
Solar Photosphere ◽  
Current Densities ◽  
The Magnetic Field

AbstractSpectro-polarimetric observations in several spectral lines allow to determine the height variation of the magnetic field of a small sunspot throughout the solar photosphere. The full Stokes-vector is measured with high spatial resolution. From these data we derive the magnetic field vector. The magnetic field strength decreases with height everywhere in the spot, even in the outer penumbra where some other authors have reported the opposite. The precise value of this decrease depends on the exact position in the spot. Values vary between 0.5 and 2.2 G km−1 when they are determined from an iron and a silicon line in the near infrared. The magnetic field is less inclined in the higher layers where the silicon line is formed. Once the magnetic vector field is known, it is straight forward to determine current densities and helicities. Current densities exhibit a radial structure in the penumbra, although it is still difficult to correlate this with the structure seen in the intensity continuum. In spite of this, current densities have a potential to serve as diagnostic tools to understand the penumbra, at least with the spatial resolution of the upcoming telescopes. The mean infered helicity is negative, as expected for a spot in the northern hemisphere. Nevertheless, there are locations inside the spot with positive helicity.

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