11
votes
Electromagnetic Eigenvalue problem in FEM yielding spurious solutions
You are correct, this formulation does introduce a spurious space. It's not actually due to any function space/discretization choice, but rather that change of variables step ($\mathbf e_t = k_z \...
10
votes
Are there any "light-weight" FEM packages around?
I've been developing a lightweight finite element library in Python 2.7 harnessing the power of NumPy arrays and SciPy sparse matrices. The general idea is that given a mesh and a finite element, you ...
5
votes
Spectral Element vs Finite Element
The SEM is a FEM! It's almost like all these different names are designed to confuse the newcomer. I will speak primarily about the most popular form which uses a tensor product Lagrange basis with ...
5
votes
Accepted
Spectral Element vs Finite Element
The main advantage is that it reduces the Runge phenomenon and leads to faster convergence rates.
It also presents less numerical dispersion and need less nodes per wavelength (see 1 and 2). So, I ...
4
votes
How to generate mesh for space-time FEM method in FEniCS?
First of all, for FEniCS specific questions please refer to the official FEniCS forum. In my opinion, your question can be answered irrespective of your FEM library of choice.
There are two ...
4
votes
Neumann BC in the current configuration in a finite-strain problem
As far as I understand, you basically want to express your traction vector from deformed (current) configuration to undeformed (reference) configuration in your integral. Would it be possible to just ...
4
votes
Are there any "light-weight" FEM packages around?
I can recommend nutils.
nutils meets at least a few your "light-weight" requirements.
it is pure python and easy to install since it only depends on standard Python libraries numpy, scipy, and ...
4
votes
Accepted
How to use MeshFunction in FEniCS (dolfin)?
The different specialized VertexFunction, EdgeFunction, FaceFunction, ...
4
votes
Are there any "light-weight" FEM packages around?
I think you have some confusion. PETSc is not in the same league as Fenics, Libmesh, Moose etc. In fact, all of these (heavyweight) packages use PETSc for linear algebra.
IMHO PETSc is as lightweight ...
2
votes
FEniCS: how to specify boundary conditions on a circle inside 2D mesh
I have also had this problem and spent a lot of time on various forums and I have finally come up with a good solution. This solution will allow you to specify a boundary condition on any whole ...
2
votes
Fenics: msh to xml conversion
meshio (a small project of mine) has as command-line tool that can do it:
meshio-convert cylinder6.msh out.xml
2
votes
Accepted
Schrödinger equation with time dependent Hamiltonian
I'd suggest to try it on your own. Do an expansion of your wavefunction in terms of spherical harmonics,
ψ(r) = ∑ℓRℓ(r,t)Yℓ0(θ,ϕ).
Note that ...
2
votes
Schrödinger equation with time dependent Hamiltonian
FEniCS users have solved this problem before, but keep in mind that FEniCS does not natively support complex numbers right now in its code. Therefore you have to make a workaround.
See: https://...
2
votes
Accepted
Penalization parameter for DG with jump penalization
TL;DR: Let k be the diffusion coefficient, θ the minimum angle between any two edges of the mesh, d the space dimension, and p the polynomial degree of the finite element basis you're ...
2
votes
Accepted
Fenics: solving the same PDE multiple times
The following approach should work.
A = assemble(a)
bc.apply(A)
solver = LUSolver(A)
solver.parameters['reuse_factorization'] = True # maybe not needed
Now you ...
2
votes
Library for Discontinuous Galerkin method: FEniCS vs deal.ii
For Hyperbolic PDEs I can highly recommend Trixi, a (if you want) high order Discontinuous Galerkin based solver with adaptive mesh refining capabilities written in ...
2
votes
Load the mesh file with boundary marks
Since GMSH was mentioned in the comments as a possible meshing tool, the common way to deal with it there is to create a Physical Line.
The simplest ...
2
votes
Accepted
How to constraint the tangential gradient on a boundary in FEniCS?
Not really a solution for FeniCS, but this is how I would solve this problem in GetFEM
...
2
votes
Accepted
How can I define an equipotential surface/volume in FEniCS?
This does not easily fit into a PDE formulation because it is a nonlocal constraint. But for all practical aspects, choosing a very large permittivity is usually good enough. Just choose it several ...
1
vote
Solving for two interconducting fluids in FEniCS
You need to define your function space of your trial and test functions as the product space of the corresponding elements.
...
1
vote
FEM with elastic inhomogeneous properties leads to mesh-induced anisotropy
I believe that the issue you are facing emanates from the type of triangular mesh you are using. This particular discretisation has in-built anisotropy; note the alignment of all of the longest edges ...
1
vote
How to use natural logarithm inside Expression on FENICS
Or simply
import math
u_e = Constant(math.log(5))
1
vote
How to use natural logarithm inside Expression on FENICS
Double quotes(" ") represent strings in python, and hence the argument of the function Expression() is a string literal rather than a floating-point number, i.e., <...
1
vote
Accepted
Solving Vectorial Poisson Equation in FENICS
Ok I will answer my own question:
The problem is in the line solve(L==a,A,bc) which needs to be replaced by solve(a==L,A,bc). ...
1
vote
How to use MeshFunction in FEniCS (dolfin)?
If you're using the latest version of FEniCS, the meshing tools are deprecated as you've noticed. These tools are now under mshr module.
You can install it via ...
1
vote
Computable alternative to "almost everywhere"
Regarding the question of how to check whether |v|<g (which I would recommend to split into v(x)<g(x) and v(x)>−g(x), since |v| will in general not be a piecewise polynomial), this is ...
1
vote
Anyone knows where I can find a simple FEniCS code where I can understand basic implantation?
You could try the FEniCS book or the FEniCS Tutorial.
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