# General Discussion **URL:** https://community.freefem.org/c/general-discussion/7.md?page=50 [Latest](https://community.freefem.org/latest.md) · [Categories](https://community.freefem.org/categories.md) **Page:** 51 --- ## [How to disable freeglut (ffglut)](https://community.freefem.org/t/how-to-disable-freeglut-ffglut/1540)
**Author:** [@rhu](https://community.freefem.org/u/rhu)\ **Replies:** 2\ **Last updated:** [February 21, 2022, 12:00pm UTC](https://community.freefem.org/t/how-to-disable-freeglut-ffglut/1540 "2022-02-21T12:00:27Z")
I only use Freefem to solve and export the solution files. Plotting is not necessary, but I get the following error message. – FreeFem++ v 3.610001 (date Mon Mar 23 07:06:46 UTC 2020) Load: lg\_fem lg\_mesh lg\_mesh3 eig… --- ## [Create common label edges between two object](https://community.freefem.org/t/create-common-label-edges-between-two-object/1499)
**Author:** [@Loic](https://community.freefem.org/u/Loic)\ **Replies:** 11\ **Last updated:** [February 21, 2022, 8:28am UTC](https://community.freefem.org/t/create-common-label-edges-between-two-object/1499 "2022-02-21T08:28:25Z")
Hello all, I have a coarse element (Object 1 in the attached picture) whose labels are 1, 2 and 3. I have the same element with perforations (Object 2). In the Object 2, all edges have the Label 0. I want that the … --- ## [Edge number/label](https://community.freefem.org/t/edge-number-label/1503)
**Author:** [@larismartins](https://community.freefem.org/u/larismartins)\ **Replies:** 2\ **Last updated:** [February 19, 2022, 7:19pm UTC](https://community.freefem.org/t/edge-number-label/1503 "2022-02-19T19:19:19Z")
Is there a way to get the edge numbering? For boundary edges and internal edges. For example: I want to number each edge from a given mesh --- ## [Edge orientation](https://community.freefem.org/t/edge-orientation/1486)
**Author:** [@larismartins](https://community.freefem.org/u/larismartins)\ **Replies:** 8\ **Last updated:** [February 19, 2022, 5:38pm UTC](https://community.freefem.org/t/edge-orientation/1486 "2022-02-19T17:38:33Z")
Is it possible to find the edge orientation on a mesh? mesh P = square(2,2); int NbTriangles = P.nt; //number of triangles plot(P, wait=1); fespace LambdaH(P, P0edge); fespace V0(P,P0); V0 u0; LambdaH l0; int nDoFu0 … --- ## [Elasticity neo-Hookean material](https://community.freefem.org/t/elasticity-neo-hookean-material/1505)
**Author:** [@amir](https://community.freefem.org/u/amir)\ **Replies:** 0\ **Last updated:** [February 17, 2022, 4:34pm UTC](https://community.freefem.org/t/elasticity-neo-hookean-material/1505 "2022-02-17T16:34:14Z")
Hi, There is an error in the following code. Would you please help me with how I can fix it?? As far as I understood, the error belongs to F11 and F22, but I don’t know why there are errors! border a1(t=0,20){x=t;y=-… --- ## [Electrostatic simulation- getting a field value](https://community.freefem.org/t/electrostatic-simulation-getting-a-field-value/1500)
**Author:** [@maya2708](https://community.freefem.org/u/maya2708)\ **Replies:** 1\ **Last updated:** [February 17, 2022, 1:01pm UTC](https://community.freefem.org/t/electrostatic-simulation-getting-a-field-value/1500 "2022-02-17T13:01:57Z")
Dear FF users and developers, I have a general question regarding Free FEM software. To be clear, I have no experience with Free FEM. I’ve read FF user manual and a few tutrorials, but I did not manage to find the answe… --- ## [Resolute Wave equation with freefem](https://community.freefem.org/t/resolute-wave-equation-with-freefem/1484)
**Author:** [@Ozeira91](https://community.freefem.org/u/Ozeira91)\ **Replies:** 4\ **Last updated:** [February 17, 2022, 12:54pm UTC](https://community.freefem.org/t/resolute-wave-equation-with-freefem/1484 "2022-02-17T12:54:59Z")
Hello everyone, I want to analyse the pressure on freefem for a tube Closed on the left side and open on the right side. We have 4 boundary conditions for the pressure (look the picture ) À Newman condition “dp/dn=0… --- ## [Large deformation strain](https://community.freefem.org/t/large-deformation-strain/1498)
**Author:** [@amir](https://community.freefem.org/u/amir)\ **Replies:** 0\ **Last updated:** [February 15, 2022, 11:27am UTC](https://community.freefem.org/t/large-deformation-strain/1498 "2022-02-15T11:27:02Z")
Hi, How can I write green strain?? I have a problem with the nonlinear term. There is einstein notation on index k. --- ## [Some problems occurred in the solution](https://community.freefem.org/t/some-problems-occurred-in-the-solution/1429)
**Author:** [@Qianrui](https://community.freefem.org/u/Qianrui)\ **Replies:** 9\ **Last updated:** [February 15, 2022, 9:14am UTC](https://community.freefem.org/t/some-problems-occurred-in-the-solution/1429 "2022-02-15T09:14:09Z")
Each time the program runs, the speed is very slow, and the following happens Error umpfack umfpack\_zl\_symbolic status -1 Error umpfack umfpack\_zl\_numeric status -4 Error umfpack\_di\_solve status -3 why? --- ## [Effect of a parameter on the result](https://community.freefem.org/t/effect-of-a-parameter-on-the-result/1495)
**Author:** [@Qianrui](https://community.freefem.org/u/Qianrui)\ **Replies:** 0\ **Last updated:** [February 15, 2022, 2:57am UTC](https://community.freefem.org/t/effect-of-a-parameter-on-the-result/1495 "2022-02-15T02:57:52Z")
Parameter w = \[0,1\], but when parameter W \> 0.1 during programming, the matrix is irreversible. Why? There have been articles about this equation in w = \[0,1\], which has a very good well posedness. --- ## [Confused by normal Nx and Ny](https://community.freefem.org/t/confused-by-normal-nx-and-ny/1492)
**Author:** [@zese](https://community.freefem.org/u/zese)\ **Replies:** 2\ **Last updated:** [February 14, 2022, 8:54am UTC](https://community.freefem.org/t/confused-by-normal-nx-and-ny/1492 "2022-02-14T08:54:22Z")
Dear all I got confused by two definitions. I read the manual and I have a question: when we have a normal velocity and want to find its x and y components we write uN.x=ux and uN.y=uy ? when we have x and y componen… --- ## [Open meshS .mesh with FreeFEM](https://community.freefem.org/t/open-meshs-mesh-with-freefem/1485)
**Author:** [@Loic](https://community.freefem.org/u/Loic)\ **Replies:** 1\ **Last updated:** [February 12, 2022, 1:38pm UTC](https://community.freefem.org/t/open-meshs-mesh-with-freefem/1485 "2022-02-12T13:38:26Z")
Circle.mesh (1000 Bytes) Hello all, I am trying to open the mesh (joint with this message). So, my script is: verbosity=0; load "msh3" meshS Th=readmesh3("Circle.mesh"); plot(Th, wait=1); But I got this error: mesh… --- ## [Force vertices coincidence at the interface of two meshes](https://community.freefem.org/t/force-vertices-coincidence-at-the-interface-of-two-meshes/1487)
**Author:** [@christof](https://community.freefem.org/u/christof)\ **Replies:** 2\ **Last updated:** [February 11, 2022, 12:14pm UTC](https://community.freefem.org/t/force-vertices-coincidence-at-the-interface-of-two-meshes/1487 "2022-02-11T12:14:39Z")
Hi, I would like to force two glued meshes to have coincident vertices on their shared border, so that it is possible to save the mesh in a file. For example, the example below: int n=8; mesh Th1=square(n,n); borde… --- ## [Savevtk with multiple scalar node field and cell scalar field](https://community.freefem.org/t/savevtk-with-multiple-scalar-node-field-and-cell-scalar-field/1483)
**Author:** [@mrbenson](https://community.freefem.org/u/mrbenson)\ **Replies:** 1\ **Last updated:** [February 10, 2022, 2:14am UTC](https://community.freefem.org/t/savevtk-with-multiple-scalar-node-field-and-cell-scalar-field/1483 "2022-02-10T02:14:49Z")
Hi, I have two questions related to the savevtk function : is there a way to save multiple (more than one) scalar node fields, in my case i need to save in the same vtu 10 scalar fields. is there a way to save a scala… --- ## [Building a Mesh in Two Steps](https://community.freefem.org/t/building-a-mesh-in-two-steps/1481)
**Author:** [@willrey](https://community.freefem.org/u/willrey)\ **Replies:** 2\ **Last updated:** [February 9, 2022, 3:12pm UTC](https://community.freefem.org/t/building-a-mesh-in-two-steps/1481 "2022-02-09T15:12:28Z")
Hi there, So that I can separate out functionality into different files, I’m trying to build one mesh from two sets of border definitions. Fundamentally, I’m trying to do this: ??? AdditionalBorders = MaterialBotto… --- ## [Access normal vector](https://community.freefem.org/t/access-normal-vector/274)
**Author:** [@BeniaminBogosel](https://community.freefem.org/u/BeniaminBogosel)\ **Replies:** 10\ **Last updated:** [February 9, 2022, 12:53pm UTC](https://community.freefem.org/t/access-normal-vector/274 "2022-02-09T12:53:16Z")
I would like to try and write some code for approximating the curvature of the boundary of the mesh. The current solution proposed in the function “curvature” does not work too well and I would like to try other variants… --- ## [Build mesh from a vector of nodes](https://community.freefem.org/t/build-mesh-from-a-vector-of-nodes/1479)
**Author:** [@larismartins](https://community.freefem.org/u/larismartins)\ **Replies:** 3\ **Last updated:** [February 9, 2022, 1:51am UTC](https://community.freefem.org/t/build-mesh-from-a-vector-of-nodes/1479 "2022-02-09T01:51:48Z")
I’m trying to build a mesh using a vector of nodes real\[int,int\] nodes = \[\[0,0\], \[0.5,0\], \[1,0\], \[0,0.5\], \[0.5,0.5\], \[1,0.5\], \[0,1\], \[0.5,1\], … --- ## [Extracting data on boundary](https://community.freefem.org/t/extracting-data-on-boundary/1469)
**Author:** [@Ajinks](https://community.freefem.org/u/Ajinks)\ **Replies:** 1\ **Last updated:** [February 6, 2022, 2:07pm UTC](https://community.freefem.org/t/extracting-data-on-boundary/1469 "2022-02-06T14:07:24Z")
Dear all, I am solving a simple mechanical problem. I am able to solve the problem. I want to get the reactions at the fixed boundary. I tried but was not able to get the values correct. Can anyone tell me how to get re… --- ## [How to compute body forces](https://community.freefem.org/t/how-to-compute-body-forces/1473)
**Author:** [@distractor](https://community.freefem.org/u/distractor)\ **Replies:** 2\ **Last updated:** [February 6, 2022, 2:01pm UTC](https://community.freefem.org/t/how-to-compute-body-forces/1473 "2022-02-06T14:01:36Z")
Hook law in weak formulation is where f are body forces (gravity for example). If there are no body forces, then the last integral simply equals zero. So I made an example, where one side of the cube as displacement… --- ## [Problem on calculating a number](https://community.freefem.org/t/problem-on-calculating-a-number/821)
**Author:** [@hezl09](https://community.freefem.org/u/hezl09)\ **Replies:** 1\ **Last updated:** [February 4, 2022, 5:17pm UTC](https://community.freefem.org/t/problem-on-calculating-a-number/821 "2022-02-04T17:17:19Z")
Hello, I met a problem in FreeFEM++ on calculating a integer number, which can be simplified as the following problem. I defined a integer M in the following two ways, and I expected that they give me the same number 2. … --- ## [Thermal body force definition](https://community.freefem.org/t/thermal-body-force-definition/1470)
**Author:** [@distractor](https://community.freefem.org/u/distractor)\ **Replies:** 6\ **Last updated:** [February 4, 2022, 3:52pm UTC](https://community.freefem.org/t/thermal-body-force-definition/1470 "2022-02-04T15:52:01Z")
Hi, I am trying to use FreeFem to solve thermal expansion, but my results make no sense. With this problem definition solve ThermoPlasticity(\[tdux, tduy, tduz\], \[vx, vy, vz\], solver = CG) = … --- ## [Apply different solution on the same mesh](https://community.freefem.org/t/apply-different-solution-on-the-same-mesh/1467)
**Author:** [@ruffi92](https://community.freefem.org/u/ruffi92)\ **Replies:** 9\ **Last updated:** [February 4, 2022, 9:09am UTC](https://community.freefem.org/t/apply-different-solution-on-the-same-mesh/1467 "2022-02-04T09:09:13Z")
Hi to all, i try to estimate the H1-seminorm error of my solution, but unfortunatly i haven’t the analytical solution. So i calculate my solution on a very dense mesh “mesh1” (around 170k vertices) to obtain the “real”… --- ## [Meshing in FreeFem++](https://community.freefem.org/t/meshing-in-freefem/1459)
**Author:** [@Ajinks](https://community.freefem.org/u/Ajinks)\ **Replies:** 3\ **Last updated:** [February 3, 2022, 3:15pm UTC](https://community.freefem.org/t/meshing-in-freefem/1459 "2022-02-03T15:15:31Z")
Hi, I am creating a 2D mesh for my crack problem. I need one edge to be discretized into 100 parts. So, I used border commands for creation. It creates mesh. but the issue here is, Freefem++ considers that edge as the bo… --- ## [Approximation of the second order derivative](https://community.freefem.org/t/approximation-of-the-second-order-derivative/1465)
**Author:** [@mariancantal](https://community.freefem.org/u/mariancantal)\ **Replies:** 1\ **Last updated:** [February 3, 2022, 12:38pm UTC](https://community.freefem.org/t/approximation-of-the-second-order-derivative/1465 "2022-02-03T12:38:08Z")
Hi! I am trying to approximate the second-order derivative using dxx(). But this gives me zero values. P1 and P2 seemed to be not working. I tried using P3 but it gave me an unstable solution. Please help me. Thank you! … --- ## [Uniform grid meshing help](https://community.freefem.org/t/uniform-grid-meshing-help/1468)
**Author:** [@sumantkr](https://community.freefem.org/u/sumantkr)\ **Replies:** 2\ **Last updated:** [February 3, 2022, 9:05am UTC](https://community.freefem.org/t/uniform-grid-meshing-help/1468 "2022-02-03T09:05:46Z")
Dear All Is there any way to generate a uniform grid for using buildmesh command? in the case of a square domain: if we use mesh Th = square(4, 5); that gives us a meshing with a uniform triangular ele… --- ## [Gmsh mesh in freefem](https://community.freefem.org/t/gmsh-mesh-in-freefem/717)
**Author:** [@LeonardoDipilato](https://community.freefem.org/u/LeonardoDipilato)\ **Replies:** 18\ **Last updated:** [February 2, 2022, 4:02pm UTC](https://community.freefem.org/t/gmsh-mesh-in-freefem/717 "2022-02-02T16:02:08Z")
I’ve been trying to export a gmsh mesh to freefem including the physical groups (for labeling purpose). Does anyone have any pointers on how to do that? I have 3 physical groups: inlet, outlet, wall (which includes all … --- ## [Interpretation Stiffness matrix P1edge/P1](https://community.freefem.org/t/interpretation-stiffness-matrix-p1edge-p1/1454)
**Author:** [@Loic](https://community.freefem.org/u/Loic)\ **Replies:** 10\ **Last updated:** [February 1, 2022, 4:16pm UTC](https://community.freefem.org/t/interpretation-stiffness-matrix-p1edge-p1/1454 "2022-02-01T16:16:54Z")
Hello all, I need some help to understand a result. I have the following mesh. I define the FE space P1edge on the Coarse mesh (mesh done only with the red edges) TH. I define the FE space P1 on the Fine mesh (all … --- ## [Normal derivative](https://community.freefem.org/t/normal-derivative/1463)
**Author:** [@zese](https://community.freefem.org/u/zese)\ **Replies:** 1\ **Last updated:** [February 1, 2022, 10:56am UTC](https://community.freefem.org/t/normal-derivative/1463 "2022-02-01T10:56:56Z")
Dear all I have two problems. first about the normal derivative. if I have a vector, u=(ux,uy) whose normal derivative is defined as du/dn. is it as : du/dn=( (dux/dx)N.x+(dux/dy)N.y , (duy/dx)N.x+(duy/dy)N.y )? or on … --- ## [Normal condition at wall](https://community.freefem.org/t/normal-condition-at-wall/1442)
**Author:** [@zese](https://community.freefem.org/u/zese)\ **Replies:** 1\ **Last updated:** [January 31, 2022, 4:19pm UTC](https://community.freefem.org/t/normal-condition-at-wall/1442 "2022-01-31T16:19:57Z")
Dear all I have a problem in defining my boundary condition. I have to define a jet on a wall (1) whose direction is normal to the wall and I just have the abs value of the jet so Vj= Aj\*(N.x+N.y) ? Aj is the magnitude… --- ## [Error on plugin c++](https://community.freefem.org/t/error-on-plugin-c/1445)
**Author:** [@larismartins](https://community.freefem.org/u/larismartins)\ **Replies:** 1\ **Last updated:** [January 31, 2022, 4:10pm UTC](https://community.freefem.org/t/error-on-plugin-c/1445 "2022-01-31T16:10:51Z")
Hi, I’m trying to execute the exemple mat\_psi.cpp but I get the following error: mat\_psi.cpp:30:10: fatal error: ff++.hpp: No such file or directory Can someone help me? [Previous page](https://community.freefem.org/c/general-discussion/7.md?page=49) [Next page](https://community.freefem.org/c/general-discussion/7.md?page=51)