Questions tagged [electromagnetism]
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89
questions
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Electric Current Module in Comsol
I am trying to solve for the potential in the electric current module in Comsol. I have a wire with 2 current boundary conditions where the in equals the out. The model can be solved in stationary but ...
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97 views
A Question About a Claim from 1991 Computational EM paper about the Cancellation of certain Boundary Terms
Please let me know if this is not the appropriate site for this question. I found questions regarding EFIE/MFIE/CFIE on this site, so I thought my question might fit.
I am studying the paper by Putnam ...
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1answer
94 views
Help with modified bessel functions
I'm trying to parse the following expression (Eq. 35 in The Magnetic Field in the Vicinity of Parallel and Twisted Three-Wire Cable Carrying Balanced Three-Phased Current) in Python and calculate its ...
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0answers
32 views
How can I improve the accuracy of the calculation of the magnetic field in Gmsh/GetDP?
I need to calculate the magnetic field along a straight line in proximity of an array of 6 magnets. I used the tutorial files "magnets" included in Gmsh and I slightly modified the file in ...
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54 views
How to use FEniCS to calculate the electric field of an isolated charged sphere
Initially I thought that this is the kind of question which ought to have already been answered in the form of an example online, but so far I haven't found one. I will admit that I am very new to ...
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65 views
How to calculate the interior value of triangular element in edge (vector) finite element?
I was using an edge (vector) finite element to solve electromagnetic diffusion (two-dimensional cases). The element that I used was a triangular element. I have got the result of the finite element in ...
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95 views
More efficient way to calculate magnetic field using Biot-Savart
I am writing a program in python that is supposed to calculate the magnetic field along a conducting coil that is made up of a bunch of points, and the magnetic field is generated by other conducting ...
1
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1answer
62 views
Simple reference problems for time harmonic Maxwell equations
For Navier-Stokes problems we can often choose a relatively simple verification problem such as the lid driven cavity, flow over a cylinder, or flow over a backward facing step to verify our ...
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71 views
Numerical scheme to calculate the normal mode of a set of hyperbolic PDEs?
I would like to solve the linearised, ideal, MHD equations, where the gas pressure is zero.
$$\frac{\partial u_x}{\partial t}=v_A^2(x,z)\left[\nabla_{||}b_x - \frac{\partial b_{||}}{\partial x}\right],...
3
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1answer
172 views
Finite difference methods in cylindrical and spherical co-ordinate systems
I am quite familiar with finite difference schemes in cartesian coordinates. The key point here is that every point in the cartesian grid is treated equally as the spacing between consecutive points ...
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32 views
COMSOL Circularl polarization
I'm having some problems trying to implement circularly polarized light in COMSOL Muliphysics.
For a isotropic homogenous media, I've obtained without problems the TE and TM reflectance curves. ...
4
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2answers
243 views
Kronecker product representation of the finite difference laplacian
The laplacian equation when discretized gives a system of linear equations that can then be solved. See the answer to this question: https://math.stackexchange.com/questions/3120948/discretization-...
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41 views
Discretisation by FVM with triangulare mesh
I work on electromagnetic modeling, and I use the finite volume method as a tool, so I want to develop code by the modified finite volume method (with triangular mesh), my problem studied is in a ...
0
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1answer
114 views
Simple particle-in-cell examples
I am studying about the 1D EM-PIC (Electro Magnetics using particle-in-cell) simulation. I want to have a simultaneous time-integration of the electric/magnetic fields plus the motion of free charges ...
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0answers
48 views
Spectral solver on em-pic
I'm recently studying for the spectral solver to implement EM-PIC code. I read an article and have some questions.
Many PIC codes uses spectral solver to overcome numerical artifacts on FDTD.
In the ...
3
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2answers
267 views
Minimum number of elements (mesh size) for electromagnetic simulation
Does someone have a reference for the minimum number of elements (or maximum mesh size) for electromagnetic simulations where a mathematical or numerical explanation is given?
I have found several ...
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132 views
Parallel plate capacitor as simple superposition of Coulomb-fields
I am trying to calculate and visualize the electric field inside and outside of a parallel plate capacitor by assuming a uniform distribution of point charges on each plate and by adding up the ...
2
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1answer
123 views
MATLAB's ode45 not dealing with initial conditions well [RESOLVED]
*Concern highlighted in yellow
*Solution at bottom
I have a differential equation to solve for the motion of an electron:
$$
\frac{d^2v}{dt^2} = \frac{1}{\gamma^6}\left( \frac{eE}{\tau m} - \left( \...
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1answer
52 views
Is there any method to incorporate minor changes into solved meshes to speed convergence in particle-in-cell solvers?
Apologies for the terrible title.
I'm trying to perform a 10^6 timestep electrostatic particle-in-cell simulation on a rather large mesh, with very limited computational resources (a single GPU). ...
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72 views
FEniCS implementation of Maxwell equations for a dipole antenna
someone knows where I can find a FEniCS implementation of Maxwell equations for a dipole or other type of antenna? I mean a dipole antenna with an arbitrary geometry of every 'leg' in the dipole.
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0answers
38 views
Multipole expansion for magneticfield intesity (magnetization)
I'm using the Barnes Hut method to calculate the magnetic vector potential induced by an applied current. Given as:
$\begin{equation} A(r) = \frac{\mu_0}{4\pi} \int_V\frac{\bf{J(r')}}{|r-r'|}dV(r') \...
3
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2answers
641 views
Electromagnetism FEM (FEniCS) interpolation - leakage effect
As for the background of what is going on:
I'm using FEniCS that is dedicated FEM solver
The problem I'm solving is magnetostatic problem where the governing PDE is $$ \bf{\nabla} \times \frac{1}{\mu}...
3
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2answers
692 views
Graphing electric potential of a ring of charge using MATLAB help
Here is a summary of what I am trying to do:
Use MATLAB to compute the potential $V$ at any point $(x, y, z)$ in space due to a uniform ring of charge. Use a Riemann sum to compute the integral ...
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1answer
73 views
Demagnetizing field using scalar potential method
I want to calculate the stray magnetic field from a ferromagnet using the scalar potential method (1). The problem consists of a ferromagnetic cuboid divided into small cuboidal cells in which the ...
-1
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1answer
58 views
Simulating magnetic particles in a field free point generated by two opposing magnets
This is probably a long shot with such a short time, but I've been trying to get theoretical data for a project I'm working on. The project involves using a very simplified version of magnetic ...
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1answer
301 views
TMZ TME modes, clarification
I'm refering here to Taflove's "computational electrodynamcis, 3rd ed."
He says
Let us assume that the structure being modeled extends to infinity in
the z-direction with no change in the shape ...
2
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0answers
44 views
Open source multiphysics software that can model the interaction of two insulators with a user-specified electrical force law?
Given two solid bodies of masses $m_1$ and $m_2$ with invariable charge distributions $\rho_1(\mathbf{r_1})$ and $\rho_2(\mathbf{r_2})$ in them,* respectively, I would like to model the electrical ...
2
votes
1answer
142 views
Average value divergence in spectral method for Poisson equation
I'd like to know how to deal with a divergence when trying to solve the Poisson equation for electrostatics with a simple spectral method. I'm not sure how to best state my problem, so I'll explain ...
2
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0answers
92 views
Solving electrostatics Poisson equation with Intel MKL routines
I am trying to solve the 3D Poisson equation
$$\nabla\cdot(\epsilon(\mathbf{r})\nabla) u(\mathbf{r}) = f(\mathbf{r})$$
I notice intel advertises routines that appear to solve
$$\nabla^2u(\mathbf{r}...
0
votes
1answer
465 views
Poincare map for Arnold-Beltrami-Childress Magnetic Field in Python
I want to plot the Poincare map for Arnold-Beltrami-Childress magnetic field for parameters $A=1, B=0.816, C=0.5773$ in Python for the Poincare section $z=0$.
Also, I am not able to understand what ...
2
votes
1answer
126 views
Magnetization Vector from XY Model for an AntiFerromagnetic System
I am working on an XY model and I'm trying to calculate the magnetization and direction for an anti-ferromagnetic (AF) system. So I have a collection of spins in the $XY$ plane represented as vectors ...
2
votes
1answer
134 views
Calculation of the EFIE integral
I need help computing the following integral:
$$
\int_{}\frac{(1+jk|\vec{r}-\vec{r}^\prime|)e^{-jk|\vec{r}-\vec{r}^\prime|}}{|\vec{r}-\vec{r}^\prime|}d\vec{r}^\prime
$$
in this integral $\vec{r}$ ...
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0answers
54 views
Magnetostatic modelling Radia: Increasing distance between magnets a produces positive force until a certain point, beyond which force goes haywire
I have two sets of magnets. One set consists of two electromagnets (Shown below: Blue) and the other set consists of two NdFeB N40 permanent magnets. Both sets of magnets lie on the same plane. I want ...
0
votes
1answer
48 views
Finite difference time domain and dynamic permittivity
Since the permittivity of any material is usually complex function of temperature, frequency, density, etc. I was wondering if it is possible to use a dynamic permittivity which changes as a function ...
0
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1answer
78 views
Help understanding this numerical surface integration technique?
I'm attempting to write a FORTRAN program that calculates the magnetic field, B, at any point outside of a bar magnet.
I'm going to use a first order euler scheme, where each side of the bar magnet ...
4
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0answers
191 views
How can I solve the wave equation for a circular rod in cylindrical coordinates using finite differences?
I have a problem with the stability of finite difference method for the wave equation in cylindrical coordinates.
the equation is:
$$
\frac{\partial^2 \omega_n}{\partial r^2}+\frac{1}{r}\frac{\...
0
votes
2answers
165 views
Nédélec Elements and Newton-Methods
If you want to develop numerical algorithms for variational inequalities, you often choose a Semismooth Newton Method. In many cases, this approach involves derivatives of $\max$ or $\min$ functions ...
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1answer
142 views
Combine Hydrodynamics and Electromagnetics
Is it possible, in general, to combine hydrodynamical motion and expansion of material with, say, a finite difference time domain method to simulate light-matter interaction?
If so, how is this done ...
1
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1answer
216 views
Introducing EigenModes from 2D FEM into 3D FEM
This particular FEM question concerns waveguides and FEM 3D simulation. To excite a waveguide with waveport (TE10 and so on), we typically have to solve for eigenvalues ($k$) of helmholtz equation ...
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0answers
550 views
Understanding Boundary Condition in FEM
I am trying to understand Dirichlet and Neumann boundary conditions in FEM and I wanted to know if my inference is correct. To articulate my understanding, lets consider a simple case of TE and TM ...
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0answers
113 views
Band structure of nonlinear Schrodinger equation with one dimensional potential
I have a nonlinear Schrodinger equation which reads:
$$ \frac{1}{2} \frac{d^2u}{dx^2}+ |u|^2u + V(x)u = -i \frac{du}{dz},$$
where $V(x)=\cos(wx)+ i a \sin(wx)$ and $w$, $a$ are numbers.
How to ...
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0answers
74 views
Numerical scheme to solve Maxwell equations with fixed potential boundaries?
We have a 2D electromagnetic field (in the sense that: $E=(E_x,E_y,0)$, $B=(0,0,B_z)$, and all derivatives with respect to $z$ are $0$), and we are considering a system made up of two walls at $x=-b$ ...
4
votes
1answer
131 views
How to force potential boundary conditions in the Yee scheme for solving Maxwell's equations?
Assume that we have a 2D electromagnetic field (in the sense that: $E=(E_x,E_y,0)$, $B=(0,0,B_z)$, and all derivatives with respect to $z$ are $0$), and that we are considering a system made up of two ...
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2answers
161 views
Rule of thumb for time-step for solving Maxwell's Equation using 3D-FDTD?
Is there something like a rule of thumb for an adequate time-step size when solving Maxwell's equation for the interaction of light with matter?
I guess a single wave oscillation has to be resolved ...
2
votes
1answer
128 views
How to deal with numerical errors in electrostatic field calculations
I want to trace electrostatic field lines emerging from 2D surfaces in 3D space. Eventually I want to find their intersection with an (uncharged) mesh.
The charge distribution $\sigma(x), x \in \...
0
votes
1answer
39 views
What software packages are designed towards modelling the radiation from accelerated charges?
I'm interested in modeling the electromagnetic fields radiated from an accelerated charge, but do not want to reinvent stuff if possible. I suspect there are software packages already out there which ...
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0answers
80 views
Can x-ray back-projection be converted to hard-field magnetic induction tomography?
This is a question about hard-field back-projection as used in x-ray tomography, applied magnetic induction tomography. Al-Zeibak and Saunders have shown that x-ray filtered backprojection can be ...
0
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1answer
96 views
Questions about implementing an electromagnetism/photonics solver package
I am hoping to start (very slowly) on implementing some form of a computational photonics/electromagnetism package. I know things like Meep, S4, FDTD++, EMPy, and a host of other proprietary/free/...
2
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1answer
75 views
Is this a proper implementation of point charge dynamics with ODEs
Since learning about point charges in my physics II class this semester, I want to be able to investigate not only the static force and field distributions but the actual trajectories of movement of ...
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1answer
912 views
Edge and Nodal finite element methods in MATLAB for Magnetic induction tomography
What is the difference between edge finite elements and nodal finite elements?
This for use in modeling the eddy current problem in classical electromagnetism. I am attempting to convert MATLAB code ...
