# General Discussion **URL:** https://community.freefem.org/c/general-discussion/7.md?page=26 [Latest](https://community.freefem.org/latest.md) · [Categories](https://community.freefem.org/categories.md) **Page:** 27 --- ## [3D elasticity problem with different Young's Modulus in the field](https://community.freefem.org/t/3d-elasticity-problem-with-different-youngs-modulus-in-the-field/2753)
**Author:** [@Gooyoon](https://community.freefem.org/u/Gooyoon)\ **Replies:** 9\ **Last updated:** [November 3, 2023, 5:59am UTC](https://community.freefem.org/t/3d-elasticity-problem-with-different-youngs-modulus-in-the-field/2753 "2023-11-03T05:59:31Z")
Dear FreeFem++ developers I’m really new to FreeFem++ I want to proceed with simulation in which young’s modulus transforms other objects by dividing them into three parts as shown in the picture below, how should I pe… --- ## [How can I convert P2 fespace data to P1](https://community.freefem.org/t/how-can-i-convert-p2-fespace-data-to-p1/2757)
**Author:** [@quenot](https://community.freefem.org/u/quenot)\ **Replies:** 3\ **Last updated:** [November 2, 2023, 8:20pm UTC](https://community.freefem.org/t/how-can-i-convert-p2-fespace-data-to-p1/2757 "2023-11-02T20:20:48Z")
Hello, I have a FreeFEM simulation that works fine with a P2 fespace but not with a P1 one. I wish to export it using pyfreefem for further manipulation and visualisation in a python environment. Unfortunately, pyfree… --- ## [Difficulty with PETSc in solving vectorized problem](https://community.freefem.org/t/difficulty-with-petsc-in-solving-vectorized-problem/2770)
**Author:** [@m.lbolok](https://community.freefem.org/u/m.lbolok)\ **Replies:** 1\ **Last updated:** [November 2, 2023, 12:18pm UTC](https://community.freefem.org/t/difficulty-with-petsc-in-solving-vectorized-problem/2770 "2023-11-02T12:18:06Z")
Hi, The problem is defined by: //===========================Code==================================== load “PETSc” macro dimension() 2// include “macro\_ddm.idp” mesh omega=square(25,25); fespace Uh(omega,\[P2,P2\]); … --- ## [Elastic structure analysis with two different material constants depending on region (can't \[region\] be specified in \[buildmesh\]?)](https://community.freefem.org/t/elastic-structure-analysis-with-two-different-material-constants-depending-on-region-cant-region-be-specified-in-buildmesh/2766)
**Author:** [@Keita](https://community.freefem.org/u/Keita)\ **Replies:** 4\ **Last updated:** [November 1, 2023, 2:41am UTC](https://community.freefem.org/t/elastic-structure-analysis-with-two-different-material-constants-depending-on-region-cant-region-be-specified-in-buildmesh/2766 "2023-11-01T02:41:28Z")
Hello, FF++ developers! I would like to do structural analysis of elastic bodies with different material constants in different regions. When creating a mesh with the square command, the \[region\] can be set, but this i… --- ## [Gmshload3 only surface elements](https://community.freefem.org/t/gmshload3-only-surface-elements/2768)
**Author:** [@ksugahar](https://community.freefem.org/u/ksugahar)\ **Replies:** 1\ **Last updated:** [October 31, 2023, 5:35pm UTC](https://community.freefem.org/t/gmshload3-only-surface-elements/2768 "2023-10-31T17:35:13Z")
We created a gmsh shape with cylinder\_Gmsh\_2D5.geo. We output cylinder\_Gmsh\_2D5.msh in Gmsh format 2.2. I am expecting a 3D cylinder (including the interior), but when I check the read labels in FreeFEM\_gmshload3.edp, … --- ## [PETSc Error on windows machine](https://community.freefem.org/t/petsc-error-on-windows-machine/2740)
**Author:** [@m.lbolok](https://community.freefem.org/u/m.lbolok)\ **Replies:** 6\ **Last updated:** [October 31, 2023, 2:42pm UTC](https://community.freefem.org/t/petsc-error-on-windows-machine/2740 "2023-10-31T14:42:55Z")
Hi, I get an error message (system error) when using PETSc on a Windows machine (AMD CPU) as follows: " The procedure entry point MPI\_Comm\_split\_type could not be located in the dynamic link library C:\\Program Files(x8… --- ## [Orthonormalization of a matrix](https://community.freefem.org/t/orthonormalization-of-a-matrix/2765)
**Author:** [@ELAchraf](https://community.freefem.org/u/ELAchraf)\ **Replies:** 0\ **Last updated:** [October 30, 2023, 3:10pm UTC](https://community.freefem.org/t/orthonormalization-of-a-matrix/2765 "2023-10-30T15:10:34Z")
Hello dear FreeFem++ community, I want to orthonormalize a rectangular real matrix A of size mxn in such a way to satisfy the property of a column-orthogonal matrix : (A)^T A = Id\_n Is there any way to do it using Fre… --- ## [Confused about correct method](https://community.freefem.org/t/confused-about-correct-method/2758)
**Author:** [@zese](https://community.freefem.org/u/zese)\ **Replies:** 4\ **Last updated:** [October 27, 2023, 12:55pm UTC](https://community.freefem.org/t/confused-about-correct-method/2758 "2023-10-27T12:55:34Z")
Dear all, I have a question about different methods of calculation of a relation. my relation is fespace Xh(th,P2); Xh U,F,GradJ; real alpha; GradJ=alpha\*F+U; I have F and U from previous solutions of PDE equations a… --- ## [PETSc : integrate surface](https://community.freefem.org/t/petsc-integrate-surface/2760)
**Author:** [@agTSL](https://community.freefem.org/u/agTSL)\ **Replies:** 7\ **Last updated:** [October 27, 2023, 10:03am UTC](https://community.freefem.org/t/petsc-integrate-surface/2760 "2023-10-27T10:03:41Z")
Dear all, I would like to calculate a surface with “int2d” but I have fews issues to find the good keyword to not take the overlap real Surf = int2d(Th3,1)( 1.0); give the surface on each local mesh Th3 I try mp… --- ## [Trying to understand difference between 3D and 2D plot](https://community.freefem.org/t/trying-to-understand-difference-between-3d-and-2d-plot/2761)
**Author:** [@jsmacd](https://community.freefem.org/u/jsmacd)\ **Replies:** 0\ **Last updated:** [October 26, 2023, 11:23pm UTC](https://community.freefem.org/t/trying-to-understand-difference-between-3d-and-2d-plot/2761 "2023-10-26T23:23:41Z")
Dear Community, I am trying to understand why in my 3D plot it looks like this function has a pole in the middle (centred along the line (0.5, 0,5 s)), but when I project it onto a 2D cross-section I no longer see this. … --- ## [Code for Dynamics of Rotating Bose-Einstein Condensate](https://community.freefem.org/t/code-for-dynamics-of-rotating-bose-einstein-condensate/2756)
**Author:** [@lchen123123](https://community.freefem.org/u/lchen123123)\ **Replies:** 0\ **Last updated:** [October 24, 2023, 1:33pm UTC](https://community.freefem.org/t/code-for-dynamics-of-rotating-bose-einstein-condensate/2756 "2023-10-24T13:33:30Z")
Dear Forum Members, I am currently working on solving the Gross-Pitaevskii (GP) equation for a rotating Bose-Einstein Condensate (BEC) in 2D and am in search of an example finite-element code that would allow me to stud… --- ## [Index of array entry?](https://community.freefem.org/t/index-of-array-entry/2755)
**Author:** [@jna1g18](https://community.freefem.org/u/jna1g18)\ **Replies:** 1\ **Last updated:** [October 21, 2023, 1:32pm UTC](https://community.freefem.org/t/index-of-array-entry/2755 "2023-10-21T13:32:19Z")
Hi all, is it possible to determine the index of a particular entry in a 1 dimensional array (i.e. a list)? E.g if I had an array A=\[3,2,8,22,1\], is there a function that would give the index of a chosen entry, maybe som… --- ## [Section 2.18 in documentation](https://community.freefem.org/t/section-2-18-in-documentation/2747)
**Author:** [@jna1g18](https://community.freefem.org/u/jna1g18)\ **Replies:** 7\ **Last updated:** [October 15, 2023, 8:11pm UTC](https://community.freefem.org/t/section-2-18-in-documentation/2747 "2023-10-15T20:11:30Z")
Apologies, I’ve asked this before, but unfortunately didn’t get a reply! So trying one more time. Hi all, section 2.18 (Tutorial to write a transient Stokes solver in matrix form) seems like it could be quite useful to … --- ## [Analyze with doxygen](https://community.freefem.org/t/analyze-with-doxygen/2749)
**Author:** [@tess35](https://community.freefem.org/u/tess35)\ **Replies:** 1\ **Last updated:** [October 12, 2023, 1:26pm UTC](https://community.freefem.org/t/analyze-with-doxygen/2749 "2023-10-12T13:26:11Z")
Hi, I would like to analyze an old Freefem code with Doxygen. It’s an open source software with some parts in C++. The authors made a good documentation, but Doxygen can produce call graph, instance graph and could help… --- ## [Stokes in Cubic Pipe](https://community.freefem.org/t/stokes-in-cubic-pipe/2744)
**Author:** [@FluidMan](https://community.freefem.org/u/FluidMan)\ **Replies:** 3\ **Last updated:** [October 10, 2023, 4:22pm UTC](https://community.freefem.org/t/stokes-in-cubic-pipe/2744 "2023-10-10T16:22:44Z")
Hello everyone, I have been using the basic features of FreeFem for years, but now I am facing a problem that I can’t seem to make sense of. Specifically, I’m struggling to implement boundary conditions for a 3D Stokes … --- ## [Solve a PDE on boundary](https://community.freefem.org/t/solve-a-pde-on-boundary/2743)
**Author:** [@zese](https://community.freefem.org/u/zese)\ **Replies:** 3\ **Last updated:** [October 9, 2023, 8:06am UTC](https://community.freefem.org/t/solve-a-pde-on-boundary/2743 "2023-10-09T08:06:14Z")
Dear all, I have a 2D axisymmetric mesh on which I am solving the optimality system. Now to update the control variable on a boundary I need to solve a PDE with some conditions. I dont know how to do that while I am on … --- ## [Interface problem](https://community.freefem.org/t/interface-problem/2739)
**Author:** [@junjie](https://community.freefem.org/u/junjie)\ **Replies:** 2\ **Last updated:** [October 7, 2023, 2:58pm UTC](https://community.freefem.org/t/interface-problem/2739 "2023-10-07T14:58:32Z")
Hello everyone, I would like to ask if the interface problem can be solved in FreeFem? The true solution u is sharded. Like the numerical example shown in the picture below. If possible, can you send me an example? Grate… --- ## [How to describe the surface of a sphere](https://community.freefem.org/t/how-to-describe-the-surface-of-a-sphere/2624)
**Author:** [@PeterQ](https://community.freefem.org/u/PeterQ)\ **Replies:** 5\ **Last updated:** [October 7, 2023, 8:19am UTC](https://community.freefem.org/t/how-to-describe-the-surface-of-a-sphere/2624 "2023-10-07T08:19:05Z")
Hello guys.I am trying to solve a pde on a sphere3. And now I want to describe the surface of a sphere3. Here are some parts of the code. solve lame(\[u1, u2, u3\], \[v1, v2, v3\]) = int3d(Th3)( lambda \* div(u1, u2, u3… --- ## [Gmsh - errror element type](https://community.freefem.org/t/gmsh-errror-element-type/2086)
**Author:** [@ftrillaudp](https://community.freefem.org/u/ftrillaudp)\ **Replies:** 3\ **Last updated:** [October 6, 2023, 2:37pm UTC](https://community.freefem.org/t/gmsh-errror-element-type/2086 "2023-10-06T14:37:36Z")
Dear all, I am starting using FreeFem++ benchmarking some code. I have created a 3D ring reusing the magnetostatic example provided in FreeFem++ website. This example in 3D does not work producing the mesh with the last… --- ## [List of edges on the mesh](https://community.freefem.org/t/list-of-edges-on-the-mesh/1841)
**Author:** [@mariancantal](https://community.freefem.org/u/mariancantal)\ **Replies:** 15\ **Last updated:** [October 4, 2023, 7:52pm UTC](https://community.freefem.org/t/list-of-edges-on-the-mesh/1841 "2023-10-04T19:52:12Z")
Hi! Is there a command in freeFEM where we can list all edges on the mesh? both internal and on the boundary? --- ## [Dirichlet boundary condition in heat equation](https://community.freefem.org/t/dirichlet-boundary-condition-in-heat-equation/2737)
**Author:** [@RaMattoso](https://community.freefem.org/u/RaMattoso)\ **Replies:** 4\ **Last updated:** [October 3, 2023, 10:19am UTC](https://community.freefem.org/t/dirichlet-boundary-condition-in-heat-equation/2737 "2023-10-03T10:19:26Z")
Hello fellows! I’m trying to implement a simple bioheat problem, but I’m having trouble with the non homogeneous boundary condition. The mesh is constructed using buildmesh and the problem is solved using varf. Mesh r… --- ## [Rate of change in temperature at everypoint on a heated circle](https://community.freefem.org/t/rate-of-change-in-temperature-at-everypoint-on-a-heated-circle/2708)
**Author:** [@M\_Usman](https://community.freefem.org/u/M_Usman)\ **Replies:** 32\ **Last updated:** [October 2, 2023, 2:00pm UTC](https://community.freefem.org/t/rate-of-change-in-temperature-at-everypoint-on-a-heated-circle/2708 "2023-10-02T14:00:25Z")
I solved a natural convection problem in a circle of radius r=0.1 with center (x0,y0)=(0.5,0.0.2\*sqrt(3)). Now I am trying to find the rate of heat transfer i.e. ∂T/∂n where n is normal at a point on a circle where we … --- ## [Umfpack\_di\_numeric failed error](https://community.freefem.org/t/umfpack-di-numeric-failed-error/2731)
**Author:** [@M\_Usman](https://community.freefem.org/u/M_Usman)\ **Replies:** 3\ **Last updated:** [October 1, 2023, 8:47am UTC](https://community.freefem.org/t/umfpack-di-numeric-failed-error/2731 "2023-10-01T08:47:13Z")
I am trying to solve natural convection flow inside a square cavity for a higher value of Rayleigh number (Ra=10^8), for this I took mesh = 200 but received “umfpack\_di\_numeric failed” error. How to deal with this proble… --- ## [Meaning of 'anisomax'?](https://community.freefem.org/t/meaning-of-anisomax/2735)
**Author:** [@jna1g18](https://community.freefem.org/u/jna1g18)\ **Replies:** 1\ **Last updated:** [October 1, 2023, 8:42am UTC](https://community.freefem.org/t/meaning-of-anisomax/2735 "2023-10-01T08:42:14Z")
Hi all, very quick question: can someone give me a brief explanation of what ‘anisomax’ in adaptmesh means? I’m assuming that it’s a measure of the anisotropy of the mesh? Many thanks! --- ## [Isoparametric Elements](https://community.freefem.org/t/isoparametric-elements/2730)
**Author:** [@yongxing](https://community.freefem.org/u/yongxing)\ **Replies:** 3\ **Last updated:** [September 30, 2023, 11:01am UTC](https://community.freefem.org/t/isoparametric-elements/2730 "2023-09-30T11:01:43Z")
Hello everyone, You know when we compute an integration int2D( ) on a triangle, we usually transform it to a standard reference triangle to compute it. We can easily use the shape function to do the transformation (iso… --- ## [Compilation Freefem code online](https://community.freefem.org/t/compilation-freefem-code-online/2734)
**Author:** [@moufide](https://community.freefem.org/u/moufide)\ **Replies:** 1\ **Last updated:** [September 29, 2023, 3:38pm UTC](https://community.freefem.org/t/compilation-freefem-code-online/2734 "2023-09-29T15:38:27Z")
Good evening to all I would like to know if it is possible to compile a Freefem code online. If so, please send me the link. Thank you --- ## [Dividing mesh into 2 domains](https://community.freefem.org/t/dividing-mesh-into-2-domains/2728)
**Author:** [@zese](https://community.freefem.org/u/zese)\ **Replies:** 3\ **Last updated:** [September 28, 2023, 4:40pm UTC](https://community.freefem.org/t/dividing-mesh-into-2-domains/2728 "2023-09-28T16:40:36Z")
Dear all, I have created a mesh in gmsh and imported to freefem. now I have a problem. I need to divide the mesh into 2 domains by creating a rectangle inside the imported domain. can I do that inside freefem or I have … --- ## [Dealing with fallback errors](https://community.freefem.org/t/dealing-with-fallback-errors/2234)
**Author:** [@jsmacd](https://community.freefem.org/u/jsmacd)\ **Replies:** 2\ **Last updated:** [September 28, 2023, 2:58pm UTC](https://community.freefem.org/t/dealing-with-fallback-errors/2234 "2023-09-28T14:58:59Z")
I’m funning FreeFEM on a macbook. My program runs on coarse grids, but when I try to refine I am getting the following error: FALLBACK (log once): Fallback to SW vertex processing (lineMode && (localGroupInfo & GLRGroup… --- ## [How to solve Possion equation have a parameter h for different values of h using loop](https://community.freefem.org/t/how-to-solve-possion-equation-have-a-parameter-h-for-different-values-of-h-using-loop/2716)
**Author:** [@M\_Usman](https://community.freefem.org/u/M_Usman)\ **Replies:** 16\ **Last updated:** [September 28, 2023, 9:09am UTC](https://community.freefem.org/t/how-to-solve-possion-equation-have-a-parameter-h-for-different-values-of-h-using-loop/2716 "2023-09-28T09:09:33Z")
Dear, I want to solve the Poisson equation involving h for different values of h given in Pram (in the following code). Then, I used a loop to pick each value from Pram as a value for h and then solve the problem. I want… --- ## [How to define signum function](https://community.freefem.org/t/how-to-define-signum-function/2727)
**Author:** [@RaghunathBandha](https://community.freefem.org/u/RaghunathBandha)\ **Replies:** 3\ **Last updated:** [September 28, 2023, 8:27am UTC](https://community.freefem.org/t/how-to-define-signum-function/2727 "2023-09-28T08:27:38Z")
I want to define sgn(x)=1 for x\>=0 and sgn(x)=-1 for x\<0. How can I define this at starting of my program in freefem. [Previous page](https://community.freefem.org/c/general-discussion/7.md?page=25) [Next page](https://community.freefem.org/c/general-discussion/7.md?page=27)