# General Discussion **URL:** https://community.freefem.org/c/general-discussion/7.md?page=6 [Latest](https://community.freefem.org/latest.md) · [Categories](https://community.freefem.org/categories.md) **Page:** 7 --- ## [FreeFEM days Thursday 18 & Friday 19, December (program and Zoom links available)](https://community.freefem.org/t/freefem-days-thursday-18-friday-19-december-program-and-zoom-links-available/4014)
**Author:** [@prj](https://community.freefem.org/u/prj)\ **Replies:** 0\ **Last updated:** [July 24, 2025, 2:18pm UTC](https://community.freefem.org/t/freefem-days-thursday-18-friday-19-december-program-and-zoom-links-available/4014 "2025-07-24T14:18:53Z")
Program and Zoom links for remote access available at: FreeFEM Days - Events. --- ## [Solve the 3D-MHD model in parallel using PETSc](https://community.freefem.org/t/solve-the-3d-mhd-model-in-parallel-using-petsc/4004)
**Author:** [@Dainy-Jia](https://community.freefem.org/u/Dainy-Jia)\ **Replies:** 9\ **Last updated:** [July 24, 2025, 2:13pm UTC](https://community.freefem.org/t/solve-the-3d-mhd-model-in-parallel-using-petsc/4004 "2025-07-24T14:13:19Z")
Hi, everyone! I want to solve a 3D MHD model, but when I used solver=UMFPACK to solve it, an error occurred on the \[16,16,16\] grid, which exceeded the memory, and the running speed was extremely slow. My aim is to obta… --- ## [Periodicity in 3D](https://community.freefem.org/t/periodicity-in-3d/4011)
**Author:** [@taha](https://community.freefem.org/u/taha)\ **Replies:** 1\ **Last updated:** [July 24, 2025, 1:58pm UTC](https://community.freefem.org/t/periodicity-in-3d/4011 "2025-07-24T13:58:31Z")
Hello everyone, i hope you are doing welle, i juste have a probleme in periodicity for this stokes probleme,"load “msh3” load “iovtk” load “medit” real pEps = 1.e-8; real r=0.05; border C01(t=-r, r){x=-1; y=t; labe… --- ## [Transfer scalar field to deformed mesh with movemesh2d](https://community.freefem.org/t/transfer-scalar-field-to-deformed-mesh-with-movemesh2d/4010)
**Author:** [@angelaros](https://community.freefem.org/u/angelaros)\ **Replies:** 4\ **Last updated:** [July 24, 2025, 11:25am UTC](https://community.freefem.org/t/transfer-scalar-field-to-deformed-mesh-with-movemesh2d/4010 "2025-07-24T11:25:38Z")
Hi, I am new to FreeFem++. I googled for the answer of this problem but without success. I need some help, please. I have an scalar field Temperature defined on a 2D mesh Th2. I deform this mesh with movemesh23 and get… --- ## [RT0Ortho FE on surface mesh](https://community.freefem.org/t/rt0ortho-fe-on-surface-mesh/4008)
**Author:** [@YYy](https://community.freefem.org/u/YYy)\ **Replies:** 0\ **Last updated:** [July 18, 2025, 8:06am UTC](https://community.freefem.org/t/rt0ortho-fe-on-surface-mesh/4008 "2025-07-18T08:06:11Z")
Hi everyone, I’m trying to use RT0Ortho on a surface mesh (meshS ThL), but it doesn’t seem to work. The interpolation matrix fails to build. Below are my code: load “msh3” load “medit” load “Element\_Mixte3d” mesh3 T… --- ## [Simulating neo-hookean material](https://community.freefem.org/t/simulating-neo-hookean-material/1480)
**Author:** [@djamel](https://community.freefem.org/u/djamel)\ **Replies:** 7\ **Last updated:** [July 17, 2025, 9:01pm UTC](https://community.freefem.org/t/simulating-neo-hookean-material/1480 "2025-07-17T21:01:12Z")
Dear all, I am using the example given in the FF documentation about “Compressible Neo-hookean materials” in the “Mathematical Models” menu. I am wondering why the program makes use of only one Lame coefficient, mu (de… --- ## [Non-linear Poisson](https://community.freefem.org/t/non-linear-poisson/4006)
**Author:** [@kelvindsou91](https://community.freefem.org/u/kelvindsou91)\ **Replies:** 1\ **Last updated:** [July 16, 2025, 9:50pm UTC](https://community.freefem.org/t/non-linear-poisson/4006 "2025-07-16T21:50:50Z")
Hi, I am trying to implement a Non-Linear Poisson Solver for heterojunctions. The weak formulation is given by Here is my code and the error I am facing regarding the optimize function. 1 : 2 : load "msh3" (alr… --- ## [“Problem” and “varf” format](https://community.freefem.org/t/problem-and-varf-format/4002)
**Author:** [@Dainy-Jia](https://community.freefem.org/u/Dainy-Jia)\ **Replies:** 4\ **Last updated:** [July 13, 2025, 1:54pm UTC](https://community.freefem.org/t/problem-and-varf-format/4002 "2025-07-13T13:54:45Z")
Hi, everyone! I have a three-dimensional model： E+u\\times B-(1/Rm)\* \\curl B=g in \\Omega (\\partial B)/(\\partial t)+\\curl E=0 in \\Omega The boundary condition is B\\cdot n=0, E\\times n=0 On … --- ## [SNES Function norm meaning](https://community.freefem.org/t/snes-function-norm-meaning/4001)
**Author:** [@ipnglt](https://community.freefem.org/u/ipnglt)\ **Replies:** 1\ **Last updated:** [July 11, 2025, 3:53pm UTC](https://community.freefem.org/t/snes-function-norm-meaning/4001 "2025-07-11T15:53:07Z")
Dear all, I am using SNESSolve to solve PDEs. During the iterative process, PETSc prints the norm of the SNES function at each iteration. I would like to understand what this SNES function norm actually represents. I tr… --- ## [Negative strain energy density](https://community.freefem.org/t/negative-strain-energy-density/3999)
**Author:** [@mllabshuji](https://community.freefem.org/u/mllabshuji)\ **Replies:** 0\ **Last updated:** [July 9, 2025, 6:48am UTC](https://community.freefem.org/t/negative-strain-energy-density/3999 "2025-07-09T06:48:11Z")
I’m a beginner and currently having trouble with analysis results. Strain energy density is not supposed to be negative, correct? However, the analysis using the code below gives negative values for it. Chat GPT and g… --- ## [Input/output issues](https://community.freefem.org/t/input-output-issues/3996)
**Author:** [@ipnglt](https://community.freefem.org/u/ipnglt)\ **Replies:** 2\ **Last updated:** [July 8, 2025, 3:44pm UTC](https://community.freefem.org/t/input-output-issues/3996 "2025-07-08T15:44:16Z")
Dear all, I am currently working on a code that computes the mean flow in a supersonic nozzle. To properly initialize each CFD run, I need to save and later read the simulation results. I chose to use ifstream and ofstr… --- ## [How to configure the solver parameters to reduce simulation time and lower memory usage](https://community.freefem.org/t/how-to-configure-the-solver-parameters-to-reduce-simulation-time-and-lower-memory-usage/3989)
**Author:** [@Lancy](https://community.freefem.org/u/Lancy)\ **Replies:** 2\ **Last updated:** [July 7, 2025, 9:35am UTC](https://community.freefem.org/t/how-to-configure-the-solver-parameters-to-reduce-simulation-time-and-lower-memory-usage/3989 "2025-07-07T09:35:58Z")
Hello, I am currently using FreeFEM to solve three-dimensional elasticity problems with approximately 5–10 million degrees of freedom, and I’ve encountered the following issue: 1.When running parallel simulations under… --- ## [How to use ParMmg for mesh adaptation when performing parallel computations within the FFDDM framework?](https://community.freefem.org/t/how-to-use-parmmg-for-mesh-adaptation-when-performing-parallel-computations-within-the-ffddm-framework/3990)
**Author:** [@Lancy](https://community.freefem.org/u/Lancy)\ **Replies:** 1\ **Last updated:** [July 3, 2025, 5:23am UTC](https://community.freefem.org/t/how-to-use-parmmg-for-mesh-adaptation-when-performing-parallel-computations-within-the-ffddm-framework/3990 "2025-07-03T05:23:38Z")
Hello, I am currently using FreeFEM to solve three-dimensional elasticity problems with approximately 5–10 million degrees of freedom. I encountered the following issues when using ParMmg for mesh adaptation. 1.In the … --- ## [The Edge03d element is used for numerical solution in freefem](https://community.freefem.org/t/the-edge03d-element-is-used-for-numerical-solution-in-freefem/3974)
**Author:** [@Dainy-Jia](https://community.freefem.org/u/Dainy-Jia)\ **Replies:** 9\ **Last updated:** [June 30, 2025, 4:37pm UTC](https://community.freefem.org/t/the-edge03d-element-is-used-for-numerical-solution-in-freefem/3974 "2025-06-30T16:37:58Z")
I have a three-dimensional model： E+u\\times B-\\curl B=g in \\Omega, E \\times n=0 on \\partal \\Omega here, u represents the velocity field, E represents the electric field, and B represents the magnetic field. … --- ## [Are the BDM2 elements stable?](https://community.freefem.org/t/are-the-bdm2-elements-stable/3987)
**Author:** [@smyrback](https://community.freefem.org/u/smyrback)\ **Replies:** 1\ **Last updated:** [June 28, 2025, 4:26pm UTC](https://community.freefem.org/t/are-the-bdm2-elements-stable/3987 "2025-06-28T16:26:29Z")
Hi, In December 2023, the BDM2 elements were added as “tests”. I’m wondering if they are working as of today? I’m using a code that uses a slightly modified version of FreeFEM as base, and when I try to incorporate the … --- ## [Complex solver despite real input](https://community.freefem.org/t/complex-solver-despite-real-input/3956)
**Author:** [@wurschtbrotwilli](https://community.freefem.org/u/wurschtbrotwilli)\ **Replies:** 5\ **Last updated:** [June 26, 2025, 5:28pm UTC](https://community.freefem.org/t/complex-solver-despite-real-input/3956 "2025-06-26T17:28:51Z")
Hello, I am dealing with Maxwell equations and want to have a vector-valued electical field whose components are complex values \[Ex,Ey,Ez\]. The imaginary part of each of the three components corresponds to the phase phi,… --- ## [Asking about the jump definition for Darcy Flow problem in Freefem](https://community.freefem.org/t/asking-about-the-jump-definition-for-darcy-flow-problem-in-freefem/3986)
**Author:** [@NhuLe](https://community.freefem.org/u/NhuLe)\ **Replies:** 0\ **Last updated:** [June 26, 2025, 3:13pm UTC](https://community.freefem.org/t/asking-about-the-jump-definition-for-darcy-flow-problem-in-freefem/3986 "2025-06-26T15:13:25Z")
Dear all experts, I’m a beginner in Freefem. I tried to write the Freefem code for the eq.(28) in the paper " Mixed Discontinuous Galerkin methods for Darcy flow. F. Brezzi, T.J.R. Hughes, L.D. Marini and A. Masud" (200… --- ## [Node values of unknown and test FE in varf](https://community.freefem.org/t/node-values-of-unknown-and-test-fe-in-varf/3950)
**Author:** [@pi.3.141](https://community.freefem.org/u/pi.3.141)\ **Replies:** 9\ **Last updated:** [June 25, 2025, 7:56am UTC](https://community.freefem.org/t/node-values-of-unknown-and-test-fe-in-varf/3950 "2025-06-25T07:56:38Z")
Hello, Wondering if it is possible to use node values of FEs in varf. Something like the following. Thank you! // mesh Th=square(10,10); fespace V1h(Th,P1); V1h u, uh; varf ma(u,uh) = int2d(Th) (u\[Th\[nuTriangle\]\[… --- ## [Block Matrices and varf](https://community.freefem.org/t/block-matrices-and-varf/3980)
**Author:** [@kelvindsou91](https://community.freefem.org/u/kelvindsou91)\ **Replies:** 3\ **Last updated:** [June 25, 2025, 7:40am UTC](https://community.freefem.org/t/block-matrices-and-varf/3980 "2025-06-25T07:40:02Z")
Hi, I’m trying to solve an eigenvalue problem for a matrix that involves second-order derivatives, such as: My initial approach was to implement each component of the matrix individually using separate varf definiti… --- ## [Request help with a 3D model](https://community.freefem.org/t/request-help-with-a-3d-model/3935)
**Author:** [@EChase](https://community.freefem.org/u/EChase)\ **Replies:** 4\ **Last updated:** [June 24, 2025, 10:44am UTC](https://community.freefem.org/t/request-help-with-a-3d-model/3935 "2025-06-24T10:44:12Z")
Good morning, Please be patient with this request. I am trying to learn Freefem, and decided to try to convert the 2D example in the documentation (under the system of elasticity) into a 3d problem. I am stuck at the … --- ## [Inconsistent rates of convergence](https://community.freefem.org/t/inconsistent-rates-of-convergence/3947)
**Author:** [@xavier1](https://community.freefem.org/u/xavier1)\ **Replies:** 8\ **Last updated:** [June 23, 2025, 11:16am UTC](https://community.freefem.org/t/inconsistent-rates-of-convergence/3947 "2025-06-23T11:16:55Z")
Hi everyone, I’m trying to compute the order of convergence for a nonlinear PDE solver using a three-level time-stepping scheme in FreeFEM++, but I’m not getting the expected results. I’m computing L2 and H1 errors agai… --- ## [Need to create nonuniform mesh on four boundaries of unit square](https://community.freefem.org/t/need-to-create-nonuniform-mesh-on-four-boundaries-of-unit-square/3981)
**Author:** [@Monirul25](https://community.freefem.org/u/Monirul25)\ **Replies:** 0\ **Last updated:** [June 23, 2025, 9:18am UTC](https://community.freefem.org/t/need-to-create-nonuniform-mesh-on-four-boundaries-of-unit-square/3981 "2025-06-23T09:18:08Z")
Hello, i have tried . Here, is my code\> real z = 5; // Stretching factor for exponential density // Exponentially stretched borders: fine near ends (i.e., corners) border bottom(t=0,1){ x=(exp(z\*t)-1)/(exp(z)-1); y=0; … --- ## [Correctness of solution for Helmholtz equation for open RF cavity?](https://community.freefem.org/t/correctness-of-solution-for-helmholtz-equation-for-open-rf-cavity/3978)
**Author:** [@Songtech-0912](https://community.freefem.org/u/Songtech-0912)\ **Replies:** 3\ **Last updated:** [June 23, 2025, 9:25am UTC](https://community.freefem.org/t/correctness-of-solution-for-helmholtz-equation-for-open-rf-cavity/3978 "2025-06-23T09:25:23Z")
I am studying a square RF cavity of side lengths L = 1 with a small aperture of radius a = 0.1 using the 2D Helmholtz equation: (\\nabla^2 + k^2)E = 0 I model the RF cavity walls as perfectly reflective, so I have Diri… --- ## [Variable formulation error](https://community.freefem.org/t/variable-formulation-error/3976)
**Author:** [@goutham2023](https://community.freefem.org/u/goutham2023)\ **Replies:** 3\ **Last updated:** [June 22, 2025, 11:01am UTC](https://community.freefem.org/t/variable-formulation-error/3976 "2025-06-22T11:01:21Z")
Hi FF Community, I have attempted to convert a gas flow problem into a varf formulation, but there seems to be an error that’s resulting in incorrect solutions. I’ve attached a screenshot of the varf statement along wit… --- ## [Petrov-Galerkin Least-Squares](https://community.freefem.org/t/petrov-galerkin-least-squares/3979)
**Author:** [@lipesantosa](https://community.freefem.org/u/lipesantosa)\ **Replies:** 6\ **Last updated:** [June 21, 2025, 9:33pm UTC](https://community.freefem.org/t/petrov-galerkin-least-squares/3979 "2025-06-21T21:33:12Z")
I’m having trouble with an Incompressible Navier Stokes script using the Petrov Galerkin method with Least Squares. matrix J = Jac(Vh2, Ph); // Matrix Jacobian matrix JGLS = GLS(Vh2, Ph); J = J + JGLS; … --- ## [Higher-order face finite elements in 3D](https://community.freefem.org/t/higher-order-face-finite-elements-in-3d/3973)
**Author:** [@kallol](https://community.freefem.org/u/kallol)\ **Replies:** 0\ **Last updated:** [June 18, 2025, 6:21am UTC](https://community.freefem.org/t/higher-order-face-finite-elements-in-3d/3973 "2025-06-18T06:21:51Z")
Are there any higher-order face finite elements (eg. P1face3d, P2face3d ) like P0face3d and P0facedc3d in 3D? --- ## [Error order problem in 3D micropolar fluid numerical simulation](https://community.freefem.org/t/error-order-problem-in-3d-micropolar-fluid-numerical-simulation/3968)
**Author:** [@AKang](https://community.freefem.org/u/AKang)\ **Replies:** 1\ **Last updated:** [June 13, 2025, 10:37am UTC](https://community.freefem.org/t/error-order-problem-in-3d-micropolar-fluid-numerical-simulation/3968 "2025-06-13T10:37:59Z")
3D micropolar fluid numerical simulation is being carried out. Using the BDF2 format, the time step is equal to the square of the space step. It is found that the L2 error of the velocity and angular velocity is a stable… --- ## [Strange behaviour of FE initialization in a loop](https://community.freefem.org/t/strange-behaviour-of-fe-initialization-in-a-loop/3962)
**Author:** [@Loic](https://community.freefem.org/u/Loic)\ **Replies:** 5\ **Last updated:** [June 10, 2025, 6:22pm UTC](https://community.freefem.org/t/strange-behaviour-of-fe-initialization-in-a-loop/3962 "2025-06-10T18:22:16Z")
Dear all, I am trying to understand the strange behaviour of the small example: mesh Th = square(1,1); macro def(i)\[i, i#B\]// EOM // vector field definition func Pk = \[P1, P1\]; fespace Wh0(Th, Pk); Wh0 de… --- ## [EigenValue, vectors and block matrices](https://community.freefem.org/t/eigenvalue-vectors-and-block-matrices/3960)
**Author:** [@ross](https://community.freefem.org/u/ross)\ **Replies:** 2\ **Last updated:** [June 10, 2025, 10:04am UTC](https://community.freefem.org/t/eigenvalue-vectors-and-block-matrices/3960 "2025-06-10T10:04:42Z")
I’m solving a simple 2D neutron diffusion problem, with delayed neutron precursors (DNPs). In steady-state, the equations look like this: We see clearly that, since we’re in steady-state, we could plug (DNP) into (N)… --- ## [Equivalent of P0edge for face in 3D](https://community.freefem.org/t/equivalent-of-p0edge-for-face-in-3d/2101)
**Author:** [@Loic](https://community.freefem.org/u/Loic)\ **Replies:** 2\ **Last updated:** [June 10, 2025, 7:50am UTC](https://community.freefem.org/t/equivalent-of-p0edge-for-face-in-3d/2101 "2025-06-10T07:50:36Z")
Dear all, Do you know if it exists an equivalent of the finite element “P0edge” in 3D (on tetrahedra), that is to say a piecewise P0 discontinuous finite element contained on each face of the mesh ? Thank you in adv… [Previous page](https://community.freefem.org/c/general-discussion/7.md?page=5) [Next page](https://community.freefem.org/c/general-discussion/7.md?page=7)