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Question

- Mar 2017

Hi,

I am looking for a FEnicS snippet code for the compressible Euler equations. Does anybody know where I could find such a snippet ?

Thanks in advance,

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Question

- Jul 2020

**I am working on multiscale modeling of composites and I want to explore the capability of FEniCS in modeling composites. Specifically, Can I assign different constitutive laws to different parts in mesh using FEniCS? Can I access the integration points to change the material behavior in a nonlinear analysis?**

**Thank you.**

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Question

- Nov 2013

I am solving PDE's numerically using FEniCS with its python interface which only saves data in pvd format. I would rather like to plot the data using MayaVi.

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Question

- May 2018

I'm trying to import an xmdf mesh file I got as an output from FEniCS into Ansys to calculate some stress values. When I try to just open the file in Ansys, I get an error message that the file cannot be open or read

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Question

- Dec 2019

Hello all,

I am experimenting with the Fenics finite element software for solving the time-harmonic Maxwell system for electromagnetic wave propagation problems. The benefit of the least squares approach is the self-adjointedness of the finite element operators that permits the use of efficient conjugate gradient solvers for very large problems using simple preconditioners (Jacobi, SOR).

The problem is that the least squares formulation suffers from non-physical loss as a result of truncation error (I suspect) in the differential operators.

I would be very interested to share experiences with people out there who have experimented with this approach in electromagnetics or fluid dynamics.

A more complete description of what I am doing can be found in the discussion on the Fenics Discourse site here: https://fenicsproject.discourse.group/t/least-squares-finite-element-formulations-for-time-harmonic-electromagnetic-fields/2024

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Question

- Jul 2014

Are there some Matlab codes of FEM for discretizing the three-dimensional Helmholtz equation with first order Sommerfeld boundary conditions? Certainly, the FEniCS package (or other C++ -based codes) for Helmholtz equations have been available online. However, I am not very be good at the these codes? In addition, if I want to write myself the Matlab codes of FEM for Helmholtz equations, what needs to be considered ? Especially, how to deal with the boundary nodes, when I evaluate the entries of stiff matrices. If who are interested into this topic, please send email (guxianming@live.cn) to me. Recently, I have a interesting ideas about a physics simulations problem, in which the 3D Helmholtz (even Maxwell ) equations are need to discretized by FEM, or weak FEM, Hybrid Discontinuous Galerkin method.

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Question

- Apr 2021

I am performing modal analysis of a Free-Free 2D beam (1 x 0.02 m) and I am trying to compute the mode frequencies and mode shapes up to the lowest 32 frequencies. Here I observed that the mode shapes started to repeat, such as

1,2,3 are rigid modes

4,5,6,7,8,9,10,12,13,14,16,17,19,20,21,23,24,26,27,29,30,32 are elastic modes

11,15,18,22,25,28,31 modes are similar to 2,4,5,6,7,8,9 modes

I used FENICS and verified in ABAQUS and got the same results.

**Is this a phenomenon or a simulation error?**

I will be using this mode data to perform Fluid-structure interaction using the modal expansion method.

**Can anyone suggest what is criteria for choosing the number of mode shapes for this method?**

**Should I include the repeated modes in the modal expansion method?**

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Question

- May 2020

Hello! I apologize for the long question, but I’m a bit lost so I’ll try to be as precise as I can.

I am trying to implement a time-domain PML formulation for wave propagation, which can be found in this work

Deleted research item The research item mentioned here has been deleted

Here, the author has developed a set of equations to deal with the wave propagation in fluid and solid medium (please refer to eq. 5.9 of the work as I can't copy-paste them here). They are valid throughout the whole domain (PML and the physical domain), and within the physical domain the equations simplify to the general wave equation.

I'm using FEniCS as the Finite Element solver, and I need to provide the weak form of the PDE I'm willing to solve. Fortunately the weak form is in the work too (please see eqs. 5.10a-d).

I'm concerned only with the wave propagation in the fluid region, so I consider only eqs. 5.10a and 5.10c. Moreover, in eq. 5.10a, I believe the term with the integral over gamma vanishes as there is no fluid-solid interface.

The problem is I need to provide the Weak Form in only one equation. I'm confused with the term d phi/dx

_{j}and I'm not sure how to rewrite eqs. 5.10a and 5.10c in the form a=L.Can someone help me with this?

Many thanks!

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