# General Discussion **URL:** https://community.freefem.org/c/general-discussion/7.md?page=72 [Latest](https://community.freefem.org/latest.md) · [Categories](https://community.freefem.org/categories.md) **Page:** 73 --- ## [Conditions au bord étirement/contraction (cas périodique)](https://community.freefem.org/t/conditions-au-bord-etirement-contraction-cas-periodique/307)
**Author:** [@Unam](https://community.freefem.org/u/Unam)\ **Replies:** 0\ **Last updated:** [March 23, 2020, 12:46pm UTC](https://community.freefem.org/t/conditions-au-bord-etirement-contraction-cas-periodique/307 "2020-03-23T12:46:59Z")
Bonjour, Je fais tourner une simulation sur les éléments finis d’ un bloc 3D périodique selon x et y. Cela simule une plaque d’épaisseur e et infini selon les axes x et y. J’aimerais fixer des contraintes au bord de c… --- ## [Formulation avec gradient](https://community.freefem.org/t/formulation-avec-gradient/304)
**Author:** [@Aicha](https://community.freefem.org/u/Aicha)\ **Replies:** 0\ **Last updated:** [March 13, 2020, 5:08pm UTC](https://community.freefem.org/t/formulation-avec-gradient/304 "2020-03-13T17:08:31Z")
Bonjour: on a l’équation: c(x) \\cdot \\nabla u=f(x,t), (x,y) \\in (0,1)^2, t \\in \[0,1\]. où c(x) est un vecteur et f une fonction. comment l’écrire en FF++? S’il vous plaît. Merci d’avance. --- ## [Faire appel à une fonction trouvée dans un autre fichier](https://community.freefem.org/t/faire-appel-a-une-fonction-trouvee-dans-un-autre-fichier/299)
**Author:** [@RahmaJERBI](https://community.freefem.org/u/RahmaJERBI)\ **Replies:** 4\ **Last updated:** [March 13, 2020, 9:30am UTC](https://community.freefem.org/t/faire-appel-a-une-fonction-trouvee-dans-un-autre-fichier/299 "2020-03-13T09:30:28Z")
Bonjour à tous, Je vous prie de bien vouloir m’aider. J’ai une fonction appelée solution et je voudrais l’utiliser dans un autre fichier. Comment faire pour l’appeler? Merci pour votre attention et votre aide. --- ## [How to get values of a pde at every position in the space?](https://community.freefem.org/t/how-to-get-values-of-a-pde-at-every-position-in-the-space/278)
**Author:** [@Mordokkai](https://community.freefem.org/u/Mordokkai)\ **Replies:** 7\ **Last updated:** [March 12, 2020, 5:51pm UTC](https://community.freefem.org/t/how-to-get-values-of-a-pde-at-every-position-in-the-space/278 "2020-03-12T17:51:52Z")
Hi, I may be asking a stupid question, but how can I get the values of the fespace after the problem was solved. Let’s say, I implemented a diffusion pde. I can plot it with the plot function of freefem++. But how can I… --- ## [Issue with movemesh](https://community.freefem.org/t/issue-with-movemesh/301)
**Author:** [@laurent.bernard](https://community.freefem.org/u/laurent.bernard)\ **Replies:** 2\ **Last updated:** [March 12, 2020, 10:10am UTC](https://community.freefem.org/t/issue-with-movemesh/301 "2020-03-12T10:10:12Z")
Hello, The following code using movemesh returns an error on FreeFEM 4.4 and 4.5 (Ubuntu 18.04): // load “msh3” load “tetgen” mesh3 Th = cube(1, 1, 1); Th=movemesh(Th,transfo=\[x+1,y,z\]); // the error message is: … --- ## [Error operation in integration](https://community.freefem.org/t/error-operation-in-integration/293)
**Author:** [@sumantkr](https://community.freefem.org/u/sumantkr)\ **Replies:** 2\ **Last updated:** [March 12, 2020, 9:24am UTC](https://community.freefem.org/t/error-operation-in-integration/293 "2020-03-12T09:24:17Z")
Dear All, This is my code and unfortunately, I am getting the same error in integral line of problem. Kindly suggest me to fix it, codes are given below. //////////////////////////////////////////////////////////////… --- ## [Issue when projecting an array onto the fespace](https://community.freefem.org/t/issue-when-projecting-an-array-onto-the-fespace/298)
**Author:** [@Mordokkai](https://community.freefem.org/u/Mordokkai)\ **Replies:** 0\ **Last updated:** [March 10, 2020, 9:45am UTC](https://community.freefem.org/t/issue-when-projecting-an-array-onto-the-fespace/298 "2020-03-10T09:45:14Z")
Hi, Let’s say I have a 2D array stored in a file: import matplotlib.pyplot as plt import numpy as np a = np.loadtxt(“w\_map.txt”) a = np.reshape(a,(624,304)) plt.imshow(a) plt.show() Then I want to use this 2D f… --- ## [Error from inporting 3D mesh in FreeFem++](https://community.freefem.org/t/error-from-inporting-3d-mesh-in-freefem/294)
**Author:** [@saptarshi](https://community.freefem.org/u/saptarshi)\ **Replies:** 2\ **Last updated:** [March 9, 2020, 6:26pm UTC](https://community.freefem.org/t/error-from-inporting-3d-mesh-in-freefem/294 "2020-03-09T18:26:19Z")
Hello I am very new to FreeFem++. I am getting a error message while trying to import a 3D mesh built in Gmsh . The error message is this read mesh ok 1Mesh3, num Tetra:= 0, num Vertice:= 0 num boundary Triangles:= 0 –… --- ## [Computing grad(u) over each triangle](https://community.freefem.org/t/computing-grad-u-over-each-triangle/287)
**Author:** [@Neutrino](https://community.freefem.org/u/Neutrino)\ **Replies:** 5\ **Last updated:** [March 5, 2020, 9:47pm UTC](https://community.freefem.org/t/computing-grad-u-over-each-triangle/287 "2020-03-05T21:47:24Z")
Hi there! I am trying to find the components of grad(w) in each triangle where w is a P1 element. Here is my code for (int i=0;i\ **Author:** [@BeniaminBogosel](https://community.freefem.org/u/BeniaminBogosel)\ **Replies:** 0\ **Last updated:** [March 5, 2020, 1:33pm UTC](https://community.freefem.org/t/operations-between-functions-in-different-fem-spaces/291 "2020-03-05T13:33:47Z") Hello, In my computation after solving some PDEs in FreeFem I often need to compute quantities related to the solution and its derivatives. Suppose I have two finite element spaces Vh(TH,P1) and Vh0(Th,P0) and u is in … --- ## [Save results in Mixed FEM](https://community.freefem.org/t/save-results-in-mixed-fem/284)
**Author:** [@Emma87](https://community.freefem.org/u/Emma87)\ **Replies:** 2\ **Last updated:** [March 5, 2020, 9:20am UTC](https://community.freefem.org/t/save-results-in-mixed-fem/284 "2020-03-05T09:20:17Z")
Dear Friends, I want to know how I can save values of a primal variable from a mixed fem formulation, for example: mesh Th=square(3,3); fespace Vh(Th, \[P1,P1\]); Vh \[u, v\]; func real initialize() { real value1 = 1.0… --- ## [Function including less than symbol](https://community.freefem.org/t/function-including-less-than-symbol/281)
**Author:** [@sumantkr](https://community.freefem.org/u/sumantkr)\ **Replies:** 5\ **Last updated:** [March 5, 2020, 6:54am UTC](https://community.freefem.org/t/function-including-less-than-symbol/281 "2020-03-05T06:54:56Z")
Dear Friends, I am new in learning FreeFEM++. Can anyone tell me about the meaning of function defined like func k= 1 + 2\*(x\<1)\*(x\>0); thanks --- ## [Problem with VTK visualisation](https://community.freefem.org/t/problem-with-vtk-visualisation/286)
**Author:** [@paolopiers](https://community.freefem.org/u/paolopiers)\ **Replies:** 2\ **Last updated:** [March 4, 2020, 5:44am UTC](https://community.freefem.org/t/problem-with-vtk-visualisation/286 "2020-03-04T05:44:11Z")
Hi everyone, today I was trying one of the examples that were worked out during the basic tutorial of FreeFem Days 2019. I was trying to visualise the mesh in Paraview. The code is correct and medit gives the right ou… --- ## [Getting adjacent vertices on the boundary of a mesh](https://community.freefem.org/t/getting-adjacent-vertices-on-the-boundary-of-a-mesh/289)
**Author:** [@BeniaminBogosel](https://community.freefem.org/u/BeniaminBogosel)\ **Replies:** 0\ **Last updated:** [March 4, 2020, 12:04am UTC](https://community.freefem.org/t/getting-adjacent-vertices-on-the-boundary-of-a-mesh/289 "2020-03-04T00:04:19Z")
Hello, I noticed that in some meshes obtained with “trunc” the boundary elements are not ordered. I wish to get access to the adjacent vertices to a vertex on the boundary. Using the boundary elements I can get one neig… --- ## [How to copy a vector from Matlab to Freefem](https://community.freefem.org/t/how-to-copy-a-vector-from-matlab-to-freefem/267)
**Author:** [@lietvo](https://community.freefem.org/u/lietvo)\ **Replies:** 2\ **Last updated:** [March 1, 2020, 6:19pm UTC](https://community.freefem.org/t/how-to-copy-a-vector-from-matlab-to-freefem/267 "2020-03-01T18:19:20Z")
Hello everyone, I want to copy a vector from Matlab which contains 1000 values to Freefem, I tried to read the manual book but I can’t see how to do it! I don’t want to do it by hand because it’s too much! So, how to do… --- ## [Issue with boundary values](https://community.freefem.org/t/issue-with-boundary-values/275)
**Author:** [@Mordokkai](https://community.freefem.org/u/Mordokkai)\ **Replies:** 1\ **Last updated:** [February 28, 2020, 9:13am UTC](https://community.freefem.org/t/issue-with-boundary-values/275 "2020-02-28T09:13:32Z")
Hi all, I don’t understand the error with this code: func real z1(){ return 10.; } problem heat(u,v) = int2d(fm)(dx(u)\*dx(v) + dy(u)dy(v)) - int2d(fm)(myHeatv) + on(0, u=z1); Error message: Impossible to cast \<11… --- ## [Variational formulation involving jumps](https://community.freefem.org/t/variational-formulation-involving-jumps/273)
**Author:** [@MCL](https://community.freefem.org/u/MCL)\ **Replies:** 0\ **Last updated:** [February 26, 2020, 11:11am UTC](https://community.freefem.org/t/variational-formulation-involving-jumps/273 "2020-02-26T11:11:16Z")
Hello everyone ! I want to solve a variational problem with the form a(u,v)=L(v) where L(v)=int1d(Th,CurveInsideTh)(jump(w)\*v) w is a discontinuous function along the curve (let us consider w as a P0 function) Is it … --- ## [Issue with boundary conditions on a basic example](https://community.freefem.org/t/issue-with-boundary-conditions-on-a-basic-example/271)
**Author:** [@Mordokkai](https://community.freefem.org/u/Mordokkai)\ **Replies:** 2\ **Last updated:** [February 26, 2020, 10:51am UTC](https://community.freefem.org/t/issue-with-boundary-conditions-on-a-basic-example/271 "2020-02-26T10:51:51Z")
Hi all, I have a warning I don’t understand about my boundary conditions: Warning: – Your set of boundary condition is incompatible with the mesh label. The basic example I’m testing is the following: border a(t=0, d… --- ## [How to solve Laplace equation with Neumann boundary condition?](https://community.freefem.org/t/how-to-solve-laplace-equation-with-neumann-boundary-condition/257)
**Author:** [@lietvo](https://community.freefem.org/u/lietvo)\ **Replies:** 8\ **Last updated:** [February 21, 2020, 2:59pm UTC](https://community.freefem.org/t/how-to-solve-laplace-equation-with-neumann-boundary-condition/257 "2020-02-21T14:59:11Z")
Hello everyone, I am using to Freefem to solve a very simple equation: Poisson equation with Neumann boundary condition. I have read the document, but it just said about the Dirichlet example! I don’t know how to put t… --- ## [Implement itereative method](https://community.freefem.org/t/implement-itereative-method/261)
**Author:** [@Healhart](https://community.freefem.org/u/Healhart)\ **Replies:** 0\ **Last updated:** [February 19, 2020, 8:52pm UTC](https://community.freefem.org/t/implement-itereative-method/261 "2020-02-19T20:52:17Z")
Hi everyone, i’m working on a fluid structure interaction problem and I want to solve it with the iteration method on the image. With Gamma\_0 a circle (r=1) contained in a bigger circle Gamma (r=6). The iteration par… --- ## [Problem import 3d mesh from gmsh](https://community.freefem.org/t/problem-import-3d-mesh-from-gmsh/256)
**Author:** [@Unam](https://community.freefem.org/u/Unam)\ **Replies:** 2\ **Last updated:** [February 19, 2020, 7:41am UTC](https://community.freefem.org/t/problem-import-3d-mesh-from-gmsh/256 "2020-02-19T07:41:46Z")
Hi, I’m trying to import a 3d mesh from gmsh to Freefem++ in order to simulate an object. The problem is that Freefem++ give me this : $ FreeFem++ real\_3d.eps – FreeFem++ v4.5 (Tue Feb 11 17:02:48 CET 2020 - git v4.5… --- ## [Eigenvalue problem for the Navier-Stokes equations](https://community.freefem.org/t/eigenvalue-problem-for-the-navier-stokes-equations/254)
**Author:** [@AntonioGarcia](https://community.freefem.org/u/AntonioGarcia)\ **Replies:** 1\ **Last updated:** [February 16, 2020, 9:12am UTC](https://community.freefem.org/t/eigenvalue-problem-for-the-navier-stokes-equations/254 "2020-02-16T09:12:33Z")
Hi, I´m trying to solve the eigenvalue problem for the Navier-Stokes equations in a 2D configuration. I’ve tried the method explained in the FreeFem manual but i haven’t find a way to adapt it to a problem with more tha… --- ## [Local matrices of the FEM](https://community.freefem.org/t/local-matrices-of-the-fem/252)
**Author:** [@isaac](https://community.freefem.org/u/isaac)\ **Replies:** 0\ **Last updated:** [February 14, 2020, 10:55pm UTC](https://community.freefem.org/t/local-matrices-of-the-fem/252 "2020-02-14T22:55:05Z")
Hi everyone! I’d like to access the local matrices. Is it possible to do it in FreeFem++? Best Regards, Isaac --- ## [How to create mesh of a medical image](https://community.freefem.org/t/how-to-create-mesh-of-a-medical-image/251)
**Author:** [@Emma87](https://community.freefem.org/u/Emma87)\ **Replies:** 0\ **Last updated:** [February 14, 2020, 7:55pm UTC](https://community.freefem.org/t/how-to-create-mesh-of-a-medical-image/251 "2020-02-14T19:55:21Z")
I am trying to create a mesh of finite elements of a medical image, I pass that format to Gmsh and then read it in FreeFem++ but I have a mistake, could you help me how to create this mesh with FreeFem, please. This is … --- ## [Problems when performing the trunc operator in 3d](https://community.freefem.org/t/problems-when-performing-the-trunc-operator-in-3d/233)
**Author:** [@Jacoban90](https://community.freefem.org/u/Jacoban90)\ **Replies:** 1\ **Last updated:** [February 13, 2020, 11:44am UTC](https://community.freefem.org/t/problems-when-performing-the-trunc-operator-in-3d/233 "2020-02-13T11:44:19Z")
Hello FreeFem community, A few weeks ago, I posted a question about defining adjacencies in a 3d mesh. Also I asked how to assign logical values to each element using a P0 fespace function in 2d. Both cases were impleme… --- ## [Save fespace array to HDF5](https://community.freefem.org/t/save-fespace-array-to-hdf5/238)
**Author:** [@nicoloabrate](https://community.freefem.org/u/nicoloabrate)\ **Replies:** 1\ **Last updated:** [February 6, 2020, 8:46am UTC](https://community.freefem.org/t/save-fespace-array-to-hdf5/238 "2020-02-06T08:46:13Z")
Dear developers, is it possible to store the problem solutions and meshes to HDF5 format, since it is included in the required packages for the installation? It would be extremely useful and faster than writing on txt f… --- ## [Computing parametric coordinates](https://community.freefem.org/t/computing-parametric-coordinates/234)
**Author:** [@mra](https://community.freefem.org/u/mra)\ **Replies:** 0\ **Last updated:** [February 5, 2020, 6:11pm UTC](https://community.freefem.org/t/computing-parametric-coordinates/234 "2020-02-05T18:11:21Z")
Hello, I have been using BAMG to construct anisotropic meshes for a while now. I am interested in knowing how to construct meshes on curved geometries. From the BAMG documentation, I see that I can provide tangents at e… --- ## [Mesh connectivity in 3d](https://community.freefem.org/t/mesh-connectivity-in-3d/223)
**Author:** [@Jacoban90](https://community.freefem.org/u/Jacoban90)\ **Replies:** 2\ **Last updated:** [February 3, 2020, 4:09pm UTC](https://community.freefem.org/t/mesh-connectivity-in-3d/223 "2020-02-03T16:09:20Z")
Hi FreeFem community, I have a 3d mesh and I need to get the data about the number of tetrahedrons and to obtain the adjacent elements of each one. According to the documentation, in 2d i can compute the number of trian… --- ## [How to make a border with lots of edges?](https://community.freefem.org/t/how-to-make-a-border-with-lots-of-edges/232)
**Author:** [@Mordokkai](https://community.freefem.org/u/Mordokkai)\ **Replies:** 1\ **Last updated:** [February 3, 2020, 8:59am UTC](https://community.freefem.org/t/how-to-make-a-border-with-lots-of-edges/232 "2020-02-03T08:59:35Z")
Hi everyone, At first I want to say that I’m not an expert neither in PDEs nor in FreeFEM. I would like to build a 2D mesh: the external border is a square (ez to do), but the internal border is a polygon with lots of e… --- ## [Composite eigenvectors with SLEPc](https://community.freefem.org/t/composite-eigenvectors-with-slepc/231)
**Author:** [@cmd](https://community.freefem.org/u/cmd)\ **Replies:** 2\ **Last updated:** [January 31, 2020, 9:48pm UTC](https://community.freefem.org/t/composite-eigenvectors-with-slepc/231 "2020-01-31T21:48:11Z")
Hi FF developers, I am solving an eigenvalue problem for a composite system using SLEPc where the problem is defined on several different FE spaces. The matrices can be built straightforwardly using blocks. However, bec… [Previous page](https://community.freefem.org/c/general-discussion/7.md?page=71) [Next page](https://community.freefem.org/c/general-discussion/7.md?page=73)