Questions tagged [electromagnetism]
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73
questions
2
votes
1answer
67 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:
$$
\frac{d^2v}{dt^2} = \frac{1}{\gamma^6}\left( \frac{eE}{\tau m} - \left( \...
1
vote
1answer
46 views
Is there any method to incorporate minor changes into solved meshes to speed convergence in particle-in-cell solvers?
Apologies for the terrible title.
I'm trying to perform a 10^6 timestep electrostatic particle-in-cell simulation on a rather large mesh, with very limited computational resources (a single GPU). ...
0
votes
0answers
53 views
FEniCS implementation of Maxwell equations for a dipole antenna
someone knows where I can find a FEniCS implementation of Maxwell equations for a dipole or other type of antenna? I mean a dipole antenna with an arbitrary geometry of every 'leg' in the dipole.
1
vote
0answers
30 views
Multipole expansion for magneticfield intesity (magnetization)
I'm using the Barnes Hut method to calculate the magnetic vector potential induced by an applied current. Given as:
$\begin{equation} A(r) = \frac{\mu_0}{4\pi} \int_V\frac{\bf{J(r')}}{|r-r'|}dV(r') \...
0
votes
0answers
65 views
Computing a double Integral using two Riemann sums & graphing multiple isosurfaces
I'm trying to compute the potential and electric field of a uniformly charged spherical shell and plot the results in the space outside the shell using MATLAB. I've tried everything from for loops to ...
3
votes
2answers
279 views
Electromagnetism FEM (FEniCS) interpolation - leakage effect
As for the background of what is going on:
I'm using FEniCS that is dedicated FEM solver
The problem I'm solving is magnetostatic problem where the governing PDE is $$ \bf{\nabla} \times \frac{1}{\mu}...
3
votes
2answers
252 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 ...
1
vote
1answer
54 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
votes
1answer
57 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 ...
0
votes
1answer
32 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
votes
0answers
42 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 ...
1
vote
1answer
88 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
votes
0answers
73 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
$$\nabla^2u(\mathbf{r}...
0
votes
1answer
266 views
Poincare map for Arnold-Beltrami-Childress Magnetic Field in Python
I want to plot the Poincare map for Arnold-Beltrami-Childress magnetic field for parameters $A=1, B=0.816, C=0.5773$ in Python for the Poincare section $z=0$.
Also, I am not able to understand what ...
2
votes
1answer
108 views
Magnetization Vector from XY Model for an AntiFerromagnetic System
I am working on an XY model and I'm trying to calculate the magnetization and direction for an anti-ferromagnetic (AF) system. So I have a collection of spins in the $XY$ plane represented as vectors ...
2
votes
1answer
112 views
Calculation of the EFIE integral
I need help computing the following integral:
$$
\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
$$
in this integral $\vec{r}$ ...
1
vote
0answers
50 views
Magnetostatic modelling Radia: Increasing distance between magnets a produces positive force until a certain point, beyond which force goes haywire
I have two sets of magnets. One set consists of two electromagnets (Shown below: Blue) and the other set consists of two NdFeB N40 permanent magnets. Both sets of magnets lie on the same plane. I want ...
0
votes
1answer
43 views
Finite difference time domain and dynamic permittivity
Since the permittivity of any material is usually complex function of temperature, frequency, density, etc. I was wondering if it is possible to use a dynamic permittivity which changes as a function ...
0
votes
1answer
73 views
Help understanding this numerical surface integration technique?
I'm attempting to write a FORTRAN program that calculates the magnetic field, B, at any point outside of a bar magnet.
I'm going to use a first order euler scheme, where each side of the bar magnet ...
4
votes
0answers
153 views
How can I solve the wave equation for a circular rod in cylindrical coordinates using finite differences?
I have a problem with the stability of finite difference method for the wave equation in cylindrical coordinates.
the equation is:
$$
\frac{\partial^2 \omega_n}{\partial r^2}+\frac{1}{r}\frac{\...
0
votes
2answers
146 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 ...
1
vote
1answer
107 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 ...
0
votes
1answer
154 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 ...
6
votes
0answers
423 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 ...
1
vote
0answers
100 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 ...
1
vote
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
122 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 ...
1
vote
2answers
136 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
124 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
38 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 ...
1
vote
0answers
76 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
votes
1answer
84 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
votes
1answer
69 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 ...
1
vote
1answer
782 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 ...
3
votes
0answers
99 views
Finite difference method for coupled PDEs: optimizing performance (time step, iterations per step)
I'm solving coupled PDEs using finite difference method: Incompressible Navier-Stokes and the divergence-free induction equation (Maxwell's equations) with non-uniform electrical conductivity. The ...
2
votes
1answer
139 views
Why FEM electric analysis gives only access to current density?
A Comsol study using frequency sweep on electric current physics yields only current density as accessible variables.
I understand the underlying equation used is Ohm's law, i.e.
$$\mathbf{J} = \...
1
vote
0answers
113 views
How to apply Dirichlet boundary condition for lowest order Nedelec element over tetrahedral domain? [closed]
The Dirichlet boundary condition is $n \times \vec{E} = n \times \vec{g}$. I don't know how to calculate the boundary value. Any kind of help would be appreciated.
1
vote
0answers
67 views
Dielectric in an external electric field
I want to numerically solve for electric field of an object in an external electric field. The object has linear displacement field such that its permitivity ($\epsilon$) is constant. The object's ...
1
vote
1answer
176 views
FEM or FD eigenvalue equation to get wave number instead of cutoff frequency
To get cutoff frequencies and eigenmode field distributions for a waveguide, one uses following equation:
$$1/\epsilon ∇ \times 1/\mu ∇ \times E = \omega^2 E$$
With $ \omega^2 $ as eigenvalues. This ...
1
vote
1answer
65 views
Suitable method for simulation of in-fiber interferometer
I am trying to simulate an optic-fiber sensor (in-fiber interferometer) to study its respond to temperature. The method I am using is finite-difference time-domain (FDTD), and I come out with a large ...
1
vote
0answers
84 views
Representing a 3D system in 2D (Electromagnetic modelling)
Ok so I'm a complete beginner in computational modelling (I use analytical methods of physics typically) but I would like to model an anisotropic, aperiodic (but not random) finite array of metallic ...
0
votes
1answer
46 views
How to introduce a distance vector when decompose a force?
I read reference (1)，but I am confused about how to introduce a distance vector in Lorentz force like the author does it in equation (11):
$$\rm J\times B = -J\cdot \nabla \left(
B\times r\right)+\...
6
votes
1answer
2k views
Simulate electric fields due to surface charges in simple circuits using python
I want to simulate the electric fields in simple circuits using Python and only free software. My first goal is to reproduce the images given in (1) which are made by the commercial ANSYS Maxwell ...
2
votes
1answer
410 views
Data analysis of a magnetic hysteresis loop
I am a physics undergrad and I have MOKE data for a magnetic material (thin permalloy film on a silicon substrate).
Here is one of the hysteresis loops I obtained, plotted using Python:
The form of ...
0
votes
2answers
4k views
Plot vector field in matlab
I have the function of an electric dipole expressed in cartesian coordinates and I want to create the vector field using Matlab .
The function is
$$E_z= \frac{p}{4\pi\epsilon_0} \cdot \left(\...
8
votes
3answers
689 views
Good introduction to numerical methods for magnetohydrodynamics (MHD)
I very recently started to read up about magnetohydrodynamics (MHD). While I have experience in the fluid part (both theory and numerics), my knowledge about the magneto part is very limited.
At the ...
1
vote
0answers
79 views
Calculating tangential electric field intensity on the boundary
I have an object with surface charge $\sigma$ for which I want to caclulate tangential electric field which would correspond to mathematical formulation:
$$
\vec{E}(\vec{x}) = \nabla_x \int \frac{\...
2
votes
1answer
329 views
I need to scale variables to solve a 2D PDE. What are the physical considerations of scaling?
I am solving a boundary value problem in 2D via an implicit finite difference scheme. Unfortunately, although the problem is well-posed and should have a unique solution, the condition number of the ...
3
votes
1answer
282 views
Finite Difference Beam Propagation Method problem
I am trying to implement the finite difference beam propagation method to study the propagation of a TE light signal through a waveguide. However, my solutions are exponentially growing, and display ...
5
votes
1answer
400 views
H(curl) conforming Nédélec-Elements to satisfy div(B)=0
Most authors are very clear that it's very dangerous to just use $\mathrm{H}(curl)$ conforming edge elements, which are divergence free, to satisfy $\mathrm{div}(\mathbf{B})=0$ and implement this ...
