# General Discussion **URL:** https://community.freefem.org/c/general-discussion/7.md?page=17 [Latest](https://community.freefem.org/latest.md) · [Categories](https://community.freefem.org/categories.md) **Page:** 18 --- ## [Mesh grid to deal with cartesian and cylindrical coordinates](https://community.freefem.org/t/mesh-grid-to-deal-with-cartesian-and-cylindrical-coordinates/3392)
**Author:** [@idk2020](https://community.freefem.org/u/idk2020)\ **Replies:** 0\ **Last updated:** [July 11, 2024, 2:20pm UTC](https://community.freefem.org/t/mesh-grid-to-deal-with-cartesian-and-cylindrical-coordinates/3392 "2024-07-11T14:20:16Z")
I want to convert the following code into Freefem++, but I am not sure how to deal with the theta variable in case i choose a square mesh and periodic boundary conditions. k = 2; a = 4; gaussian\_like\_tanh = @(x) tanh(… --- ## [Error with restrict() and loaded mesh](https://community.freefem.org/t/error-with-restrict-and-loaded-mesh/3385)
**Author:** [@etj](https://community.freefem.org/u/etj)\ **Replies:** 2\ **Last updated:** [July 11, 2024, 10:35am UTC](https://community.freefem.org/t/error-with-restrict-and-loaded-mesh/3385 "2024-07-11T10:35:01Z")
Hello, I am having problems using restrict() with a mesh loaded with loadDmesh(). Here is a MWE that returns an error when either of the last 2 lines is not commented. Could you please tell me if I am doing something w… --- ## [Same code, different freefem versions, but different results](https://community.freefem.org/t/same-code-different-freefem-versions-but-different-results/3383)
**Author:** [@pi.3.141etc](https://community.freefem.org/u/pi.3.141etc)\ **Replies:** 2\ **Last updated:** [July 9, 2024, 2:23pm UTC](https://community.freefem.org/t/same-code-different-freefem-versions-but-different-results/3383 "2024-07-09T14:23:17Z")
Hello everybody, I am new to Freefem. I am experimenting with the code from Bertand Maury and collaborators, found here https://www.imo.universite-paris-saclay.fr/~bertrand.maury/Files/NSpenal.edp . When I run the cod… --- ## [DG for incompressible NSE](https://community.freefem.org/t/dg-for-incompressible-nse/3357)
**Author:** [@Ravi](https://community.freefem.org/u/Ravi)\ **Replies:** 5\ **Last updated:** [July 9, 2024, 1:03pm UTC](https://community.freefem.org/t/dg-for-incompressible-nse/3357 "2024-07-09T13:03:13Z")
In the above trilinear form we need to use the convect(.) operator for first term but for other terms how we can write them in freefem. --- ## [simply supported beam](https://community.freefem.org/t/simply-supported-beam/3380)
**Author:** [@Kevin](https://community.freefem.org/u/Kevin)\ **Replies:** 1\ **Last updated:** [July 9, 2024, 12:36pm UTC](https://community.freefem.org/t/simply-supported-beam/3380 "2024-07-09T12:36:51Z")
Good day, I am trying to make a simulation of the elastic analysis of a steel beam simply supported with a point load in the program, to make the review with my teachers we observed that the data are fine, but not having… --- ## [Mistake in the documentation on functions](https://community.freefem.org/t/mistake-in-the-documentation-on-functions/3387)
**Author:** [@AdityasOcean](https://community.freefem.org/u/AdityasOcean)\ **Replies:** 0\ **Last updated:** [July 6, 2024, 1:17am UTC](https://community.freefem.org/t/mistake-in-the-documentation-on-functions/3387 "2024-07-06T01:17:15Z")
The function dyy has a typo error under documentation. Please check the link - Functions --- ## [DG Pressure Correction for Navier Stokes](https://community.freefem.org/t/dg-pressure-correction-for-navier-stokes/3386)
**Author:** [@Ravi](https://community.freefem.org/u/Ravi)\ **Replies:** 0\ **Last updated:** [July 5, 2024, 1:36pm UTC](https://community.freefem.org/t/dg-pressure-correction-for-navier-stokes/3386 "2024-07-05T13:36:42Z")
Hello everyone, I am trying to apply DG for pressure correction scheme of navier stokes equation. In the code the bilinear form,:- problem U (\[uu1,uu2\], \[v1,v2\])= int2d(Th) (uu1v1+uu2v2) + int2d(Th) (phidt(dx(v1) +… --- ## [How to deal with "out of memory"](https://community.freefem.org/t/how-to-deal-with-out-of-memory/3358)
**Author:** [@LXX](https://community.freefem.org/u/LXX)\ **Replies:** 0\ **Last updated:** [June 27, 2024, 9:08am UTC](https://community.freefem.org/t/how-to-deal-with-out-of-memory/3358 "2024-06-27T09:08:45Z")
Hello everyone, I am a beginner of freefem++. For the freefem++ code, I can only solve PDEs in a single thread. I want to use Freefem++ to solve the unsteady incompressible magnetohydrodynamic equations. I read a pa… --- ## [Simulation of inflating a balloon or membrane](https://community.freefem.org/t/simulation-of-inflating-a-balloon-or-membrane/3378)
**Author:** [@piotrne](https://community.freefem.org/u/piotrne)\ **Replies:** 0\ **Last updated:** [July 4, 2024, 4:58am UTC](https://community.freefem.org/t/simulation-of-inflating-a-balloon-or-membrane/3378 "2024-07-04T04:58:31Z")
Hello, I want to simulate the deformation of a thin, flexible material (membrane) under the influence of air pressure acting from below. The edge of the membrane is attached to a plane and air is pumped between this pla… --- ## [Problem related to SUPG](https://community.freefem.org/t/problem-related-to-supg/3026)
**Author:** [@FilippoVaselli](https://community.freefem.org/u/FilippoVaselli)\ **Replies:** 7\ **Last updated:** [July 3, 2024, 6:11am UTC](https://community.freefem.org/t/problem-related-to-supg/3026 "2024-07-03T06:11:41Z")
I am trying to solve the Navier Stokes equation in a driven cavity but i am acctually having problem with adding the stabilization term related to SUPG. Freefam can only solve weak formulation problem and in the integra… --- ## [Finite volume and anisotropic mesh](https://community.freefem.org/t/finite-volume-and-anisotropic-mesh/3309)
**Author:** [@Ali](https://community.freefem.org/u/Ali)\ **Replies:** 6\ **Last updated:** [July 2, 2024, 2:40pm UTC](https://community.freefem.org/t/finite-volume-and-anisotropic-mesh/3309 "2024-07-02T14:40:02Z")
Hello, My question is : Is it possible to solve Euler’s equation using the Finite Volume Method with an anisotropic mesh in FreeFem++? Thank you in advance for your answer. --- ## [Navier Stokes with Newton method](https://community.freefem.org/t/navier-stokes-with-newton-method/3371)
**Author:** [@Loic](https://community.freefem.org/u/Loic)\ **Replies:** 6\ **Last updated:** [July 1, 2024, 3:22pm UTC](https://community.freefem.org/t/navier-stokes-with-newton-method/3371 "2024-07-01T15:22:19Z")
Dear all, I am trying to solve the Navier Stokes problem (a channel flow with a parabolic inflow) using the Newton method. I have the following code (inspired from what I have found on the FreeFEM tutorial Newton Method… --- ## [Assistance with Peclet Number Calculation in FreeFem++](https://community.freefem.org/t/assistance-with-peclet-number-calculation-in-freefem/3360)
**Author:** [@noureddine](https://community.freefem.org/u/noureddine)\ **Replies:** 1\ **Last updated:** [June 29, 2024, 11:57pm UTC](https://community.freefem.org/t/assistance-with-peclet-number-calculation-in-freefem/3360 "2024-06-29T23:57:48Z")
Hi everyone, I would like to ask if there is any previous code where the calculation of the Peclet number was addressed. I tried to calculate it myself, but I am not getting reasonable results. I think I might have made… --- ## [Solution to the Poisson Boltzmann equation](https://community.freefem.org/t/solution-to-the-poisson-boltzmann-equation/3337)
**Author:** [@EJimenez](https://community.freefem.org/u/EJimenez)\ **Replies:** 3\ **Last updated:** [June 28, 2024, 9:35pm UTC](https://community.freefem.org/t/solution-to-the-poisson-boltzmann-equation/3337 "2024-06-28T21:35:33Z")
Hello community, I am new to using FreeFem++. I have been trying to solve the Poisson-Boltzmann equation, however the code I am using does not solve said equation. I attach the image of the equations I am trying to solve… --- ## [Hele shaw flow problem](https://community.freefem.org/t/hele-shaw-flow-problem/3352)
**Author:** [@111-1111](https://community.freefem.org/u/111-1111)\ **Replies:** 2\ **Last updated:** [June 28, 2024, 9:10am UTC](https://community.freefem.org/t/hele-shaw-flow-problem/3352 "2024-06-28T09:10:18Z")
Dear developer: I’m solving for a hele shaw flow over a rectangular region (2×1). The boundary conditions on all four edges are no-flux boundary conditions. The code I developed fails to converge.Note that If the nonlin… --- ## [Fast computation of bilinear forms](https://community.freefem.org/t/fast-computation-of-bilinear-forms/3355)
**Author:** [@jcvillaquira](https://community.freefem.org/u/jcvillaquira)\ **Replies:** 2\ **Last updated:** [June 27, 2024, 4:45am UTC](https://community.freefem.org/t/fast-computation-of-bilinear-forms/3355 "2024-06-27T04:45:31Z")
Hi, I have the bilinear form q that can be represented as q(f, g) = int2d(Th)( b \* ( dx(uf) \* dx(ug) + dy(uf) \* dy(ug) ) ) where b is a fixed function, uf and ug solve a given BVP (details of the specific problem are no… --- ## [Sample code for homogenization](https://community.freefem.org/t/sample-code-for-homogenization/3356)
**Author:** [@mas](https://community.freefem.org/u/mas)\ **Replies:** 0\ **Last updated:** [June 27, 2024, 1:41am UTC](https://community.freefem.org/t/sample-code-for-homogenization/3356 "2024-06-27T01:41:14Z")
Is there a sample program to calculate the homogenized modulus of elasticity of a unit cell using the homogenization method? --- ## [SVDSolve with two matrices (generalized SVD)](https://community.freefem.org/t/svdsolve-with-two-matrices-generalized-svd/3348)
**Author:** [@etj](https://community.freefem.org/u/etj)\ **Replies:** 5\ **Last updated:** [June 26, 2024, 9:18am UTC](https://community.freefem.org/t/svdsolve-with-two-matrices-generalized-svd/3348 "2024-06-26T09:18:22Z")
Hello, I am wondering if one can use SVDSolve(...) with two matrices? Something similar to EPSSolve(J,M,...) for generalized eigenvalue problems. From SLEPc’s documentation it seems that it’s possible (e.g. here), but … --- ## [Regional attributes](https://community.freefem.org/t/regional-attributes/3338)
**Author:** [@qingYang](https://community.freefem.org/u/qingYang)\ **Replies:** 9\ **Last updated:** [June 25, 2024, 11:53am UTC](https://community.freefem.org/t/regional-attributes/3338 "2024-06-25T11:53:07Z")
Hello everyone, may I ask how the Regional attributes in the regionlist are generated when using Tetgen to generate mesh? how to get “145” as follow? real\[int\] domain =\[1.5,pi,0.75,145,0.0025\]; mesh3 Thfinal = tetg(Th3… --- ## [Inforce homogeneous Neumann BCs using DG FEM](https://community.freefem.org/t/inforce-homogeneous-neumann-bcs-using-dg-fem/3339)
**Author:** [@noureddine](https://community.freefem.org/u/noureddine)\ **Replies:** 3\ **Last updated:** [June 24, 2024, 1:44pm UTC](https://community.freefem.org/t/inforce-homogeneous-neumann-bcs-using-dg-fem/3339 "2024-06-24T13:44:36Z")
Dear experts, I am currently working on implementing the discontinuous Galerkin Finite Element Method (DG-FEM) for solving the Richards equation in a square domain with homogeneous Neumann boundary conditions on the lat… --- ## [Error in FreeFEM Solving Equations with Time Terms](https://community.freefem.org/t/error-in-freefem-solving-equations-with-time-terms/3341)
**Author:** [@doublehai](https://community.freefem.org/u/doublehai)\ **Replies:** 1\ **Last updated:** [June 24, 2024, 10:28am UTC](https://community.freefem.org/t/error-in-freefem-solving-equations-with-time-terms/3341 "2024-06-24T10:28:25Z")
I am a beginner in finite element methods and I am using FreeFem++to solve parabolic equations. However, I encountered a problem: when I solved the Posion equation without a time term, the refinement grid error and error… --- ## [Composite FE spaces + Parallel assembly with PETSc](https://community.freefem.org/t/composite-fe-spaces-parallel-assembly-with-petsc/3336)
**Author:** [@pierreT](https://community.freefem.org/u/pierreT)\ **Replies:** 6\ **Last updated:** [June 23, 2024, 8:30pm UTC](https://community.freefem.org/t/composite-fe-spaces-parallel-assembly-with-petsc/3336 "2024-06-23T20:30:44Z")
Hello, I am a user of version 4.14, and I’ve run the test cases presented here: https://doc.freefem.org/documentation/composite.html#with-petsc I have a problem with parallel assembly + PETSc. Compared with the parall… --- ## [Weak form definition](https://community.freefem.org/t/weak-form-definition/3325)
**Author:** [@Walid](https://community.freefem.org/u/Walid)\ **Replies:** 11\ **Last updated:** [June 23, 2024, 5:28pm UTC](https://community.freefem.org/t/weak-form-definition/3325 "2024-06-23T17:28:44Z")
Dear All, i am asking for your kind support for the below problem I am trying to write the weak form of the below PDE ∂n/∂t +∇⋅(W.n+D∇n)=S where: W drift velocity n unknow concentration D the diffusion coefficient … --- ## [Issue on dual-cpu server with Windows 11](https://community.freefem.org/t/issue-on-dual-cpu-server-with-windows-11/3331)
**Author:** [@quentin](https://community.freefem.org/u/quentin)\ **Replies:** 3\ **Last updated:** [June 21, 2024, 10:37am UTC](https://community.freefem.org/t/issue-on-dual-cpu-server-with-windows-11/3331 "2024-06-21T10:37:13Z")
Dear all, I am unable to use all the cores to run my FreeFEM code. My FreeFEM version is 4.14 and the OS is Windows11. My machine is equipped with dual AMD 7003 series CPUs, each have 64 cores. My code uses PETSc, it w… --- ## [Composite Fe spaces](https://community.freefem.org/t/composite-fe-spaces/2596)
**Author:** [@mhg](https://community.freefem.org/u/mhg)\ **Replies:** 3\ **Last updated:** [July 12, 2023, 6:09pm UTC](https://community.freefem.org/t/composite-fe-spaces/2596 "2023-07-12T18:09:20Z")
Thank you for including composite FE spaces in version 4.13 as announced in https://community.freefem.org/t/equations-involve-different-mesh-spaces/2453/2. Is there also a documentation available for this feature? I no… --- ## [Third derivative](https://community.freefem.org/t/third-derivative/3068)
**Author:** [@111-1111](https://community.freefem.org/u/111-1111)\ **Replies:** 18\ **Last updated:** [June 20, 2024, 1:00pm UTC](https://community.freefem.org/t/third-derivative/3068 "2024-06-20T13:00:16Z")
Hello developer, I am a beginner about this software.I encountered difficulties in solving the following problem In the above equation system, I have two questions. I am not very clear about the correct expression of … --- ## [How to solve the following PDEs in Freefem](https://community.freefem.org/t/how-to-solve-the-following-pdes-in-freefem/3326)
**Author:** [@zcwang6](https://community.freefem.org/u/zcwang6)\ **Replies:** 1\ **Last updated:** [June 20, 2024, 11:21am UTC](https://community.freefem.org/t/how-to-solve-the-following-pdes-in-freefem/3326 "2024-06-20T11:21:01Z")
Dear freefem team, I am currently trying to implement the following method in freefem. In the section 2.1 of the paper, it includes 3 pdes for solving. The last one is the elasticity equation which is clear to me, h… --- ## [Inviscid Incompressible Flow in FreeFEM](https://community.freefem.org/t/inviscid-incompressible-flow-in-freefem/3284)
**Author:** [@airwarriorg91](https://community.freefem.org/u/airwarriorg91)\ **Replies:** 72\ **Last updated:** [June 20, 2024, 10:37am UTC](https://community.freefem.org/t/inviscid-incompressible-flow-in-freefem/3284 "2024-06-20T10:37:27Z")
Hello ! I am trying to solve the incompressible and invsicid flow in FreeFEM for a 3D geometry. I have written the code to work in parallel using PETSc. The mesh is imported from GMSH mesh file. I am not sure what is wr… --- ## [Different spaces for different variables](https://community.freefem.org/t/different-spaces-for-different-variables/3321)
**Author:** [@Luanusp](https://community.freefem.org/u/Luanusp)\ **Replies:** 9\ **Last updated:** [June 19, 2024, 2:21pm UTC](https://community.freefem.org/t/different-spaces-for-different-variables/3321 "2024-06-19T14:21:57Z")
Dear, i’m a beginner to this program and I was trying to implement a problem linked to the 1D heat equation. According to the author, I need to use P1 to approximate the time variable and P3 for the space variable. Howev… --- ## [First guess for the Navier-Stokes and heat equations](https://community.freefem.org/t/first-guess-for-the-navier-stokes-and-heat-equations/3322)
**Author:** [@lee-maximee](https://community.freefem.org/u/lee-maximee)\ **Replies:** 1\ **Last updated:** [June 19, 2024, 10:29am UTC](https://community.freefem.org/t/first-guess-for-the-navier-stokes-and-heat-equations/3322 "2024-06-19T10:29:11Z")
I want to solve the incompressible Navier-Stokes equations (NVSE) coupled with a heat equation (convection and diffusion term). The variables are the velocity vector (u, v), the pressure p and the temperature T. The temp… [Previous page](https://community.freefem.org/c/general-discussion/7.md?page=16) [Next page](https://community.freefem.org/c/general-discussion/7.md?page=18)