# General Discussion **URL:** https://community.freefem.org/c/general-discussion/7.md?page=13 [Latest](https://community.freefem.org/latest.md) · [Categories](https://community.freefem.org/categories.md) **Page:** 14 --- ## [Computing vorticity axisymmetric](https://community.freefem.org/t/computing-vorticity-axisymmetric/3637)
**Author:** [@zese](https://community.freefem.org/u/zese)\ **Replies:** 1\ **Last updated:** [December 17, 2024, 8:46am UTC](https://community.freefem.org/t/computing-vorticity-axisymmetric/3637 "2024-12-17T08:46:55Z")
Dear all I want to compute vorticity in axisymmetric flow. The components are as follows: what to do to overcome singularity for axial vorticity at r=0 in FF++? BR --- ## [The boundary condition of Hall-MHD model](https://community.freefem.org/t/the-boundary-condition-of-hall-mhd-model/3484)
**Author:** [@weixj](https://community.freefem.org/u/weixj)\ **Replies:** 11\ **Last updated:** [December 17, 2024, 7:48am UTC](https://community.freefem.org/t/the-boundary-condition-of-hall-mhd-model/3484 "2024-12-17T07:48:59Z")
Hello, everyone. Now I’m using freefem++ to solve the incompressible hall-MHD equations, but I’ve encountered a problem regarding the boundary conditions of the magnetic field. \\mu\\nabla\\times (\\nabla\\times\\mathbf{B})+… --- ## [Mixed finite element in parallel](https://community.freefem.org/t/mixed-finite-element-in-parallel/3634)
**Author:** [@abdobenf](https://community.freefem.org/u/abdobenf)\ **Replies:** 7\ **Last updated:** [December 16, 2024, 7:41pm UTC](https://community.freefem.org/t/mixed-finite-element-in-parallel/3634 "2024-12-16T19:41:31Z")
Hello, I have a mixed finite element method, I would like to implement it where I assemble the matrix for each variable and then assemble the global matrix like G = \[\[A,B\], \[C,D\]\], is there anyway to do this in parallel… --- ## [How to use mAL preconditioner with periodic boundary](https://community.freefem.org/t/how-to-use-mal-preconditioner-with-periodic-boundary/3627)
**Author:** [@quentin](https://community.freefem.org/u/quentin)\ **Replies:** 5\ **Last updated:** [December 16, 2024, 1:27pm UTC](https://community.freefem.org/t/how-to-use-mal-preconditioner-with-periodic-boundary/3627 "2024-12-16T13:27:41Z")
I tried to modify boundary condition in natural-convection-fieldsplit-2d-PETSc.edp to have a periodic boundary pair \[2,4\]. But it reports an error in the line set(dA, fieldsplit = 0... How to fix it? Best Regards. --- ## [What does the array of \`\`data\[ \]'' represent during the process of adding a new finite element?](https://community.freefem.org/t/what-does-the-array-of-data-represent-during-the-process-of-adding-a-new-finite-element/3635)
**Author:** [@Alex2019](https://community.freefem.org/u/Alex2019)\ **Replies:** 0\ **Last updated:** [December 16, 2024, 12:44pm UTC](https://community.freefem.org/t/what-does-the-array-of-data-represent-during-the-process-of-adding-a-new-finite-element/3635 "2024-12-16T12:44:06Z")
Hello all, I would like to add a new finite element 2010–A nonstandard mixed finite element family.pdf (170.3 KB) in FreeFem as https://doc.freefem.org/documentation/developers.html. However, I am unable to provide t… --- ## [Databased nonlinear coefficients](https://community.freefem.org/t/databased-nonlinear-coefficients/3626)
**Author:** [@Phuang](https://community.freefem.org/u/Phuang)\ **Replies:** 0\ **Last updated:** [December 14, 2024, 2:18pm UTC](https://community.freefem.org/t/databased-nonlinear-coefficients/3626 "2024-12-14T14:18:12Z")
Hi, I am exploring the possibilities to use FreeFem to solve electromagnetic problem using the test date for coefficients. Specifically, I have test data for magnetic permeability /mu which depends on the solution. I sea… --- ## [New space for FreeFEM](https://community.freefem.org/t/new-space-for-freefem/3624)
**Author:** [@candy](https://community.freefem.org/u/candy)\ **Replies:** 5\ **Last updated:** [December 13, 2024, 6:56am UTC](https://community.freefem.org/t/new-space-for-freefem/3624 "2024-12-13T06:56:14Z")
Hello, everyone! Is there a space like this? The space of functions which are constant over the whole domain. It is employed to model concepts such as global constraints. Any comments are welcome. --- ## [Need programming speed fast](https://community.freefem.org/t/need-programming-speed-fast/3625)
**Author:** [@Monirul25](https://community.freefem.org/u/Monirul25)\ **Replies:** 0\ **Last updated:** [December 13, 2024, 3:59am UTC](https://community.freefem.org/t/need-programming-speed-fast/3625 "2024-12-13T03:59:08Z")
Hi, i am using windows 11. Is there anyway to make programming speed fast on windows 10 and windows 11?. --- ## [FreeFEM days Thursday 12 & Friday 13, December (schedule and Zoom links available)](https://community.freefem.org/t/freefem-days-thursday-12-friday-13-december-schedule-and-zoom-links-available/3588)
**Author:** [@prj](https://community.freefem.org/u/prj)\ **Replies:** 1\ **Last updated:** [December 11, 2024, 1:11pm UTC](https://community.freefem.org/t/freefem-days-thursday-12-friday-13-december-schedule-and-zoom-links-available/3588 "2024-12-11T13:11:29Z")
More at FreeFEM Days - Events. --- ## [3D beginner Problem](https://community.freefem.org/t/3d-beginner-problem/3623)
**Author:** [@Ravi](https://community.freefem.org/u/Ravi)\ **Replies:** 4\ **Last updated:** [December 10, 2024, 12:30pm UTC](https://community.freefem.org/t/3d-beginner-problem/3623 "2024-12-10T12:30:22Z")
I don’t understand what I have done wrong here. It will be very helpful if someone clarifies why this cube is showing in red color. --- ## [How to use mean-zero pressure space in FreeFem](https://community.freefem.org/t/how-to-use-mean-zero-pressure-space-in-freefem/3570)
**Author:** [@Ravi](https://community.freefem.org/u/Ravi)\ **Replies:** 7\ **Last updated:** [December 9, 2024, 9:20am UTC](https://community.freefem.org/t/how-to-use-mean-zero-pressure-space-in-freefem/3570 "2024-12-09T09:20:13Z")
It will be very helpful if anyone can explain how to use mean-zero pressure space in Free Fem. I am talking about the space M\_h0 in the attached file. --- ## [Obtaining Current Date/Time](https://community.freefem.org/t/obtaining-current-date-time/3556)
**Author:** [@AllBall](https://community.freefem.org/u/AllBall)\ **Replies:** 4\ **Last updated:** [December 9, 2024, 6:59am UTC](https://community.freefem.org/t/obtaining-current-date-time/3556 "2024-12-09T06:59:31Z")
Hi Freefem community, I am reaching out to you to ask about possible ways to obtain the current date/time in my script, as I would like to create a folder with the date and time labeled to organize my plots in. Upon di… --- ## [Mesh Challenges: Non-drawable Sections and Outer Ring Uniformity](https://community.freefem.org/t/mesh-challenges-non-drawable-sections-and-outer-ring-uniformity/3620)
**Author:** [@MariamiMamgo](https://community.freefem.org/u/MariamiMamgo)\ **Replies:** 1\ **Last updated:** [December 9, 2024, 4:46am UTC](https://community.freefem.org/t/mesh-challenges-non-drawable-sections-and-outer-ring-uniformity/3620 "2024-12-09T04:46:21Z")
Hello, everyone, In the EDP file I am working with, I am encountering two issues: Incomplete Mesh: I am unable to build the entire mesh. Specifically, the lower half remains non-drawable. Could someone explain why thi… --- ## [Newbie question about integrating](https://community.freefem.org/t/newbie-question-about-integrating/3621)
**Author:** [@oldoldman](https://community.freefem.org/u/oldoldman)\ **Replies:** 1\ **Last updated:** [December 9, 2024, 4:02am UTC](https://community.freefem.org/t/newbie-question-about-integrating/3621 "2024-12-09T04:02:08Z")
Hi guys, Have a look at the following script mesh m2=square(1,1); cout \<\< int1d(m2)(2) \<\< " " \<\< int2d(m2)(2) \<\< "\\n"; I have some basic idea of integrating , which means sum something up. The script outputs 4 and 2. … --- ## [Mesh error after adding file output code](https://community.freefem.org/t/mesh-error-after-adding-file-output-code/3618)
**Author:** [@zxss](https://community.freefem.org/u/zxss)\ **Replies:** 2\ **Last updated:** [December 8, 2024, 10:03am UTC](https://community.freefem.org/t/mesh-error-after-adding-file-output-code/3618 "2024-12-08T10:03:24Z")
Hi, everyone. I meet a strange problem when I implement my fsi of a falling ball, as you can see in my upload. The code can operate for the full 6 seconds successfully firstly. However, after adding file output code, it… --- ## [Non linear source term in heat equation](https://community.freefem.org/t/non-linear-source-term-in-heat-equation/3615)
**Author:** [@441998gg](https://community.freefem.org/u/441998gg)\ **Replies:** 3\ **Last updated:** [December 5, 2024, 12:33pm UTC](https://community.freefem.org/t/non-linear-source-term-in-heat-equation/3615 "2024-12-05T12:33:45Z")
Hello everyone, I am trying to solve an heat diffusion equation which has a non linear source term. when i am trying to compile it is showing the linear combination error (error operator ( \<10LinearCombI7MGauche4C\_F0E\>,… --- ## [Using Raviart-Thomas elements on a surface mesh](https://community.freefem.org/t/using-raviart-thomas-elements-on-a-surface-mesh/3614)
**Author:** [@yowie](https://community.freefem.org/u/yowie)\ **Replies:** 0\ **Last updated:** [December 4, 2024, 4:42pm UTC](https://community.freefem.org/t/using-raviart-thomas-elements-on-a-surface-mesh/3614 "2024-12-04T16:42:58Z")
Hey y’all! As a part of my master thesis, I’m trying to implement a mixed finite element method for a diffusion equation on a curved surface. This means that I have to use RT0 finite elements on a meshS. The problem is … --- ## [RT1 space results](https://community.freefem.org/t/rt1-space-results/3611)
**Author:** [@AzizTakhirov](https://community.freefem.org/u/AzizTakhirov)\ **Replies:** 3\ **Last updated:** [December 4, 2024, 10:31am UTC](https://community.freefem.org/t/rt1-space-results/3611 "2024-12-04T10:31:01Z")
Hi everyone, I’m confused with the results I’m getting with the RT1 space for the mixed formulation of the Poisson Equation. I adapted the LaplaceRT.edp code to have an analytical solution. When I use the RT0&P0 pair, … --- ## [Periodic mesh advection](https://community.freefem.org/t/periodic-mesh-advection/3612)
**Author:** [@quentin](https://community.freefem.org/u/quentin)\ **Replies:** 0\ **Last updated:** [December 3, 2024, 2:28pm UTC](https://community.freefem.org/t/periodic-mesh-advection/3612 "2024-12-03T14:28:18Z")
How to track a moving Lagrangian boundary with L-periodic in x direction? I know such problem is solved by Alan Riquier, Numerical study of a viscous breaking water wave and the limit of vanishing viscosity In s… --- ## [Problem in computing discontinuous Galerkin method for incompressible Stokes equation](https://community.freefem.org/t/problem-in-computing-discontinuous-galerkin-method-for-incompressible-stokes-equation/801)
**Author:** [@kallol](https://community.freefem.org/u/kallol)\ **Replies:** 3\ **Last updated:** [December 2, 2024, 6:48am UTC](https://community.freefem.org/t/problem-in-computing-discontinuous-galerkin-method-for-incompressible-stokes-equation/801 "2024-12-02T06:48:32Z")
I am trying to compute incompressible steady Stokes equation by using discontinuous Galerkin SIPG method. But in FreeFem++ the operators jump and mean giving error message for using vector valued finite element function … --- ## [Cantilever beam vibration modes](https://community.freefem.org/t/cantilever-beam-vibration-modes/3605)
**Author:** [@HMasson](https://community.freefem.org/u/HMasson)\ **Replies:** 5\ **Last updated:** [November 28, 2024, 1:22pm UTC](https://community.freefem.org/t/cantilever-beam-vibration-modes/3605 "2024-11-28T13:22:46Z")
Hello, I am trying to compute the vibration modes of a cantilever beam in 3D for different material densities. It can be summarized as solving an eigenvalue problem using stiffness and mass matrices. Here is the code … --- ## [3D mesh for paraview](https://community.freefem.org/t/3d-mesh-for-paraview/2380)
**Author:** [@jsmacd](https://community.freefem.org/u/jsmacd)\ **Replies:** 4\ **Last updated:** [November 26, 2024, 8:00am UTC](https://community.freefem.org/t/3d-mesh-for-paraview/2380 "2024-11-26T08:00:20Z")
I’ve saved some 3D data as a vtu file so that I can look at it in Paraview. However, in Paraview I am seeing only the solution along the boundary. When I try to use the volume filter, it states that I don’t have tetrahed… --- ## [To find the Order of Convergence of the heat equation when exact solution is not given](https://community.freefem.org/t/to-find-the-order-of-convergence-of-the-heat-equation-when-exact-solution-is-not-given/3601)
**Author:** [@Monirul25](https://community.freefem.org/u/Monirul25)\ **Replies:** 2\ **Last updated:** [November 25, 2024, 4:44pm UTC](https://community.freefem.org/t/to-find-the-order-of-convergence-of-the-heat-equation-when-exact-solution-is-not-given/3601 "2024-11-25T16:44:25Z")
Hi, i am trying to find order of convergence of heat equation when exact solution is not given only data is given. My code is running but it is not giving optimal results. Can you help me please. Here, is my code. Hea… --- ## [Number of elements different from what is imposed with buildmesh](https://community.freefem.org/t/number-of-elements-different-from-what-is-imposed-with-buildmesh/3593)
**Author:** [@jbl](https://community.freefem.org/u/jbl)\ **Replies:** 2\ **Last updated:** [November 25, 2024, 8:11am UTC](https://community.freefem.org/t/number-of-elements-different-from-what-is-imposed-with-buildmesh/3593 "2024-11-25T08:11:43Z")
Hello, I am doing a simple simulation on a domain with 2 triangular elements. Unfortunately I noticed that the build mesh command sometimes creates 4 triangular elements. For example I did this real l =40; real h =3; … --- ## [Is the following code is correct?](https://community.freefem.org/t/is-the-following-code-is-correct/3590)
**Author:** [@Monirul25](https://community.freefem.org/u/Monirul25)\ **Replies:** 8\ **Last updated:** [November 22, 2024, 11:13am UTC](https://community.freefem.org/t/is-the-following-code-is-correct/3590 "2024-11-22T11:13:34Z")
Can someone help me how to write the second term of the bilinear form?? Here is my code Blockquote +intalledges(Th)((abs(N.xmean(v1old)+N.ymean(v2old))jump(v1)jump(vv1))/nTonEdge(nTonEdge-1)) +int1d(Th)(abs(N.xv… --- ## [10.0014 + 0.0000123456 = 10.0014?](https://community.freefem.org/t/10-0014-0-0000123456-10-0014/3461)
**Author:** [@hanweiwei](https://community.freefem.org/u/hanweiwei)\ **Replies:** 9\ **Last updated:** [November 21, 2024, 2:13pm UTC](https://community.freefem.org/t/10-0014-0-0000123456-10-0014/3461 "2024-11-21T14:13:26Z")
Hi everyone, I have a question, for example. we define real a = 10.0014 and real b = 0.0000123456 then we compute a+b by using FreeFem we obtain a+b = 10.0014, however the ture is 10.0014123456 so how can we avoid s… --- ## [About tetrahedron definition](https://community.freefem.org/t/about-tetrahedron-definition/3587)
**Author:** [@raphael](https://community.freefem.org/u/raphael)\ **Replies:** 3\ **Last updated:** [November 21, 2024, 1:40pm UTC](https://community.freefem.org/t/about-tetrahedron-definition/3587 "2024-11-21T13:40:13Z")
Can I directly define a tetrahedral mesh in FreeFEM++ using mesh3 Th = tetrahedron(10, 10, 10, \[0, 1\], \[0, 1\], \[0, 1\]);, or are there any prerequisites? Thank you everyone! --- ## [How write code of product of average in FreeFem++](https://community.freefem.org/t/how-write-code-of-product-of-average-in-freefem/3583)
**Author:** [@Monirul25](https://community.freefem.org/u/Monirul25)\ **Replies:** 4\ **Last updated:** [November 21, 2024, 10:32am UTC](https://community.freefem.org/t/how-write-code-of-product-of-average-in-freefem/3583 "2024-11-21T10:32:09Z")
Hi, i am getting a term as following: intalledges(Th) ((average(v1vv1) +average(v2vv2)) /nTonEdge\*(nTonEdge-1)) , where v1, v2 are unkowns and vv1 and vv2 are test functions. How, incorporate this term in FreeFem++??. … --- ## [Surface gradient](https://community.freefem.org/t/surface-gradient/3589)
**Author:** [@yongxing](https://community.freefem.org/u/yongxing)\ **Replies:** 1\ **Last updated:** [November 20, 2024, 12:59pm UTC](https://community.freefem.org/t/surface-gradient/3589 "2024-11-20T12:59:25Z")
Is there an example about surface gradient and PDE? Thank you in advance! --- ## [About definition](https://community.freefem.org/t/about-definition/3586)
**Author:** [@raphael](https://community.freefem.org/u/raphael)\ **Replies:** 1\ **Last updated:** [November 20, 2024, 6:47am UTC](https://community.freefem.org/t/about-definition/3586 "2024-11-20T06:47:00Z")
I would like to ask how to define a three-dimensional curl operator in FreeFEM++ so that it can be used later in “solve…= int3d curlu\*curlv” sorry guys :smiling\_face\_with\_tear: i am a new guy [Previous page](https://community.freefem.org/c/general-discussion/7.md?page=12) [Next page](https://community.freefem.org/c/general-discussion/7.md?page=14)