# General Discussion **URL:** https://community.freefem.org/c/general-discussion/7.md?page=66 [Latest](https://community.freefem.org/latest.md) · [Categories](https://community.freefem.org/categories.md) **Page:** 67 --- ## [Plots in different graphic windows](https://community.freefem.org/t/plots-in-different-graphic-windows/676)
**Author:** [@e-aranda](https://community.freefem.org/u/e-aranda)\ **Replies:** 1\ **Last updated:** [December 7, 2020, 4:29pm UTC](https://community.freefem.org/t/plots-in-different-graphic-windows/676 "2020-12-07T16:29:13Z")
Hi, Is it possible to show two plots in different windows at the same time? Thanks, Ernesto --- ## [Energy term in wave equation simulation](https://community.freefem.org/t/energy-term-in-wave-equation-simulation/672)
**Author:** [@mordechaiy](https://community.freefem.org/u/mordechaiy)\ **Replies:** 5\ **Last updated:** [December 2, 2020, 7:22pm UTC](https://community.freefem.org/t/energy-term-in-wave-equation-simulation/672 "2020-12-02T19:22:53Z")
Dear users, I have to implement an energy term defined by E(t)= integral2d (u\_t^2+c^2\*(u\_x^2+u\_y^2)); The domain of the integral is the square \[0,3\]X\[0,3\]: I defined: real x0=0.0,y0=0.0; real xF=3.0,yF=3.0; int n=… --- ## [Adding noise to data](https://community.freefem.org/t/adding-noise-to-data/673)
**Author:** [@mordechaiy](https://community.freefem.org/u/mordechaiy)\ **Replies:** 2\ **Last updated:** [December 2, 2020, 10:49am UTC](https://community.freefem.org/t/adding-noise-to-data/673 "2020-12-02T10:49:23Z")
Dear users, I would like to add noise to data in my code using FF++, Can anyone send please an example of adding noise? Thanks in advance, Mordechai. --- ## [StabFem (a Matlab/Octave interface to FreeFem)](https://community.freefem.org/t/stabfem-a-matlab-octave-interface-to-freefem/655)
**Author:** [@david.fabre](https://community.freefem.org/u/david.fabre)\ **Replies:** 5\ **Last updated:** [December 1, 2020, 9:31pm UTC](https://community.freefem.org/t/stabfem-a-matlab-octave-interface-to-freefem/655 "2020-12-01T21:31:13Z")
Dear FreeFem developers & users. We are happy to announce a new stable release of the StabFem project. StabFem is a Matlab/Octave interface to FreeFem which allows to launch your programs, manipulate and plot your resul… --- ## [Info about mesh quality](https://community.freefem.org/t/info-about-mesh-quality/662)
**Author:** [@Lily](https://community.freefem.org/u/Lily)\ **Replies:** 4\ **Last updated:** [December 1, 2020, 9:21pm UTC](https://community.freefem.org/t/info-about-mesh-quality/662 "2020-12-01T21:21:04Z")
Dear FreeFem users, I’d like to know if there is an option to get information about mesh quality such as : the quality of a tetrahedron, or the quality of all elements and indicate the worst one the volume of a tetrah… --- ## [Refinement with splitmesh](https://community.freefem.org/t/refinement-with-splitmesh/668)
**Author:** [@IF300](https://community.freefem.org/u/IF300)\ **Replies:** 1\ **Last updated:** [November 27, 2020, 8:12am UTC](https://community.freefem.org/t/refinement-with-splitmesh/668 "2020-11-27T08:12:15Z")
Hi, I am trying to implement a problem with refinement of the mesh (2D) based on some local error estimation. The refinement is done by adding nodes and edges into some elements (they are selected thanks to the local er… --- ## [Issue with transfer between two meshes](https://community.freefem.org/t/issue-with-transfer-between-two-meshes/667)
**Author:** [@christof](https://community.freefem.org/u/christof)\ **Replies:** 7\ **Last updated:** [November 24, 2020, 9:54pm UTC](https://community.freefem.org/t/issue-with-transfer-between-two-meshes/667 "2020-11-24T21:54:49Z")
Hello, I am having an issue when using the transfer routine when trying to copy variables from one mesh to another. I have used the following Maxwell 3D example: https://github.com/FreeFem/FreeFem-sources/blob/develop/e… --- ## [Sum of functions](https://community.freefem.org/t/sum-of-functions/666)
**Author:** [@mordechaiy](https://community.freefem.org/u/mordechaiy)\ **Replies:** 2\ **Last updated:** [November 23, 2020, 5:28pm UTC](https://community.freefem.org/t/sum-of-functions/666 "2020-11-23T17:28:18Z")
Dear FF++ users I would like to ask please, I have functions which are connected via an index “i” how can I sum these functions concerning this index? For example, if I define macro kappai(x,y,xi,yi) ((x-xi)^2+(y-yi… --- ## [Mesh "Matryoshka"](https://community.freefem.org/t/mesh-matryoshka/663)
**Author:** [@Raffa2s](https://community.freefem.org/u/Raffa2s)\ **Replies:** 2\ **Last updated:** [November 20, 2020, 3:32pm UTC](https://community.freefem.org/t/mesh-matryoshka/663 "2020-11-20T15:32:24Z")
Hi, I had created a mesh using meshS and I want to put another meshs inside it in a specific position. The other meshes are created with GMSH. Do you know how to do that? Thank you --- ## [FreeFEM days Thursday 10 & Friday 11, December (virtual conference)](https://community.freefem.org/t/freefem-days-thursday-10-friday-11-december-virtual-conference/664)
**Author:** [@prj](https://community.freefem.org/u/prj)\ **Replies:** 0\ **Last updated:** [November 20, 2020, 1:52pm UTC](https://community.freefem.org/t/freefem-days-thursday-10-friday-11-december-virtual-conference/664 "2020-11-20T13:52:20Z")
Link for the registration form: here. --- ## [Interpolation issues](https://community.freefem.org/t/interpolation-issues/661)
**Author:** [@mordechaiy](https://community.freefem.org/u/mordechaiy)\ **Replies:** 0\ **Last updated:** [November 20, 2020, 1:01am UTC](https://community.freefem.org/t/interpolation-issues/661 "2020-11-20T01:01:31Z")
Dear FF++ developers and participants, I have created FF++ code for the 2D wave equation in a square with a hole, and save the values of the solution for each point of the mesh, and for each time of the forward proble… --- ## [GMSH and FREEFEM for 3D meshes](https://community.freefem.org/t/gmsh-and-freefem-for-3d-meshes/650)
**Author:** [@bcaval](https://community.freefem.org/u/bcaval)\ **Replies:** 20\ **Last updated:** [November 18, 2020, 6:15pm UTC](https://community.freefem.org/t/gmsh-and-freefem-for-3d-meshes/650 "2020-11-18T18:15:57Z")
Hi everybody, I have some doubts on the correct use of GMSH and Freefem for 3D meshes. (1) I would like to understand what is the difference between : load “msh3” load “gmsh” mesh3 Th = gmshload3(“maillage.msh”); a… --- ## [Transient heat transfer problem with FreeFem++](https://community.freefem.org/t/transient-heat-transfer-problem-with-freefem/657)
**Author:** [@Mik](https://community.freefem.org/u/Mik)\ **Replies:** 1\ **Last updated:** [November 18, 2020, 7:30am UTC](https://community.freefem.org/t/transient-heat-transfer-problem-with-freefem/657 "2020-11-18T07:30:02Z")
Dear all, I am willing to solve a basic transient heat transfer problem with Freefelm++. While solving, I am facing the issue of a minimum temperature of 100K, which normally should not be the case with my problem. Here… --- ## [Different labels to a uniform mesh in domain with a hole & scattered field](https://community.freefem.org/t/different-labels-to-a-uniform-mesh-in-domain-with-a-hole-scattered-field/616)
**Author:** [@mordechaiy](https://community.freefem.org/u/mordechaiy)\ **Replies:** 3\ **Last updated:** [November 15, 2020, 4:08pm UTC](https://community.freefem.org/t/different-labels-to-a-uniform-mesh-in-domain-with-a-hole-scattered-field/616 "2020-11-15T16:08:29Z")
Hi, I created a uniform mesh for a square with a hole using the “square” and “trunc” commands in FF++. Thus, the domain has two boundaries, outer and inner. I would like to ask please, how to ask FF++ to assign a diff… --- ## [Label number for a domain with hole](https://community.freefem.org/t/label-number-for-a-domain-with-hole/654)
**Author:** [@mordechaiy](https://community.freefem.org/u/mordechaiy)\ **Replies:** 0\ **Last updated:** [November 14, 2020, 7:03pm UTC](https://community.freefem.org/t/label-number-for-a-domain-with-hole/654 "2020-11-14T19:03:25Z")
hi to everyone, I would like to ask please; I created a square with a hole using the commands “square” and then “trunc”. I wrote the following code in FF++ for the square domain with a hole : //parameters real x0=-… --- ## [Complex polynomial eigenvalue problem with Morley elements using SLEPc](https://community.freefem.org/t/complex-polynomial-eigenvalue-problem-with-morley-elements-using-slepc/651)
**Author:** [@AntoniJ](https://community.freefem.org/u/AntoniJ)\ **Replies:** 1\ **Last updated:** [November 12, 2020, 7:00pm UTC](https://community.freefem.org/t/complex-polynomial-eigenvalue-problem-with-morley-elements-using-slepc/651 "2020-11-12T19:00:09Z")
Dear developers, I am trying to use SLEPc to solve a complex polynomial eigenvalue problem with a sequential program (I don’t need to parallelize it yet) and the command PEPSolve doesn’t seem to be implemented, at least… --- ## [Periodic condition in FEM space](https://community.freefem.org/t/periodic-condition-in-fem-space/649)
**Author:** [@RYP](https://community.freefem.org/u/RYP)\ **Replies:** 6\ **Last updated:** [November 11, 2020, 4:17pm UTC](https://community.freefem.org/t/periodic-condition-in-fem-space/649 "2020-11-11T16:17:42Z")
Hi everybody, I want to know how the function “periodic” work in FEM space. For example, If I define fespace Vh(Th, P1, periodic = \[\[1, x\], \[3, x\], \[2, y\], \[4, y\]\]) with mesh Th = square(2, 2). Is it equivalent to d… --- ## [Quadrilateral element](https://community.freefem.org/t/quadrilateral-element/637)
**Author:** [@guanzhen](https://community.freefem.org/u/guanzhen)\ **Replies:** 1\ **Last updated:** [November 10, 2020, 2:58pm UTC](https://community.freefem.org/t/quadrilateral-element/637 "2020-11-10T14:58:35Z")
Dear friends, I am a new user of FreeFem, reading all the contents of the documentation, I see that only Triangular/Tetrahedral elements are supported. However, I would like to work with Quadrilateral elements. Is thi… --- ## [Segmentation fault with signed distance](https://community.freefem.org/t/segmentation-fault-with-signed-distance/638)
**Author:** [@Lily](https://community.freefem.org/u/Lily)\ **Replies:** 5\ **Last updated:** [November 10, 2020, 9:44am UTC](https://community.freefem.org/t/segmentation-fault-with-signed-distance/638 "2020-11-10T09:44:23Z")
Hello, I have just installed FreeFem++ 4.7-1. There is a segmentation fault when trying to use the external library “distance”. I have already identify that the segmentation fault comes from the distance command and n… --- ## [Tensor properties by domain (ex : Cijkl) on a single varf](https://community.freefem.org/t/tensor-properties-by-domain-ex-cijkl-on-a-single-varf/641)
**Author:** [@bcaval](https://community.freefem.org/u/bcaval)\ **Replies:** 0\ **Last updated:** [November 6, 2020, 7:11pm UTC](https://community.freefem.org/t/tensor-properties-by-domain-ex-cijkl-on-a-single-varf/641 "2020-11-06T19:11:29Z")
Hi everybody, I work on a thermoelastic problem but with general elasticity Cijkl. I have 3 domains, but also we could have more. And I wrote fespace Ph(Th3,P0); Ph\[int\] c(37); for (i=1;i\<=6;i++) { for (j=1;j\<=6;j++… --- ## [Gmsh and freefem](https://community.freefem.org/t/gmsh-and-freefem/352)
**Author:** [@mrbenson](https://community.freefem.org/u/mrbenson)\ **Replies:** 8\ **Last updated:** [November 6, 2020, 7:04pm UTC](https://community.freefem.org/t/gmsh-and-freefem/352 "2020-11-06T19:04:29Z")
Hi, I’m quite new, i’d like to use freefem with gmsh file mesh. LoadMesh function make easy to import a 2D gmsh mesh file and labels(Th) function give all physical boundary tags (dim=1). 1 - I’d like to know how to ge… --- ## [Malloc() error on Ubuntu](https://community.freefem.org/t/malloc-error-on-ubuntu/634)
**Author:** [@Lily](https://community.freefem.org/u/Lily)\ **Replies:** 11\ **Last updated:** [November 5, 2020, 10:13am UTC](https://community.freefem.org/t/malloc-error-on-ubuntu/634 "2020-11-05T10:13:23Z")
Hello, I’m using FreeFem on Ubuntu 20.04 and I have a strange issue. I simply want to glue two meshes with the command “Th = Th1 + Th2”. It returns the error “malloc(): invalid size (unsorted) Abandon (core dumped)” … --- ## [Help on magnetostatic problem](https://community.freefem.org/t/help-on-magnetostatic-problem/633)
**Author:** [@dajopez](https://community.freefem.org/u/dajopez)\ **Replies:** 1\ **Last updated:** [November 3, 2020, 11:02am UTC](https://community.freefem.org/t/help-on-magnetostatic-problem/633 "2020-11-03T11:02:26Z")
Hello, I would like to model a ferrofluid droplet as it deforms in a magnetic field. I know the equations, but I was wondering how to get a shape to dynamically change in free-fem, or if this is something more appropria… --- ## [Convection-diffusion problem with pre-computed velocity field](https://community.freefem.org/t/convection-diffusion-problem-with-pre-computed-velocity-field/630)
**Author:** [@G\_B](https://community.freefem.org/u/G_B)\ **Replies:** 1\ **Last updated:** [November 3, 2020, 10:52am UTC](https://community.freefem.org/t/convection-diffusion-problem-with-pre-computed-velocity-field/630 "2020-11-03T10:52:23Z")
Dear FreeFem users, I’m trying to solve a convection-diffusion problem of this form: \\partial\_t c - K\\triangle c + \\nabla\\cdot(u c) - B(cv - c)=0 where K is the diffusion coefficient and it is constant, the term B(cv … --- ## [Integration over a part of the big domain](https://community.freefem.org/t/integration-over-a-part-of-the-big-domain/435)
**Author:** [@sgkkr](https://community.freefem.org/u/sgkkr)\ **Replies:** 8\ **Last updated:** [October 28, 2020, 10:28am UTC](https://community.freefem.org/t/integration-over-a-part-of-the-big-domain/435 "2020-10-28T10:28:01Z")
I have a mesh defined on x as (-20,20) and y as (-20,20). The mesh space is defined on this domain lengths. However I would like to integrate a P2 variable over a certain part of the domain given by x’=(-2,10) and y’=(-2… --- ## [Boundary conditions from finite difference to FreeFem](https://community.freefem.org/t/boundary-conditions-from-finite-difference-to-freefem/627)
**Author:** [@sgkkr](https://community.freefem.org/u/sgkkr)\ **Replies:** 0\ **Last updated:** [October 27, 2020, 8:11pm UTC](https://community.freefem.org/t/boundary-conditions-from-finite-difference-to-freefem/627 "2020-10-27T20:11:51Z")
I have 1-dimensional velocity field, defined in a finite difference space and I would like to import the 1-D velocity field and use it as a boundary condition on the inlet of the finite element mesh. Is there is an easy … --- ## [Second Order Temporal Discretization: Crank-Nicolson](https://community.freefem.org/t/second-order-temporal-discretization-crank-nicolson/623)
**Author:** [@D\_N\_Sarkar](https://community.freefem.org/u/D_N_Sarkar)\ **Replies:** 4\ **Last updated:** [October 24, 2020, 4:15pm UTC](https://community.freefem.org/t/second-order-temporal-discretization-crank-nicolson/623 "2020-10-24T16:15:22Z")
I am trying to make an unsteady incompressible isothermal Navier-Stokes FreeFEM code for 2D lid-driven cavity flow for high Reynolds number (Re). The “convect” interpolation operator allows first order discretization. Ho… --- ## [A problem of stability](https://community.freefem.org/t/a-problem-of-stability/139)
**Author:** [@xlzheng](https://community.freefem.org/u/xlzheng)\ **Replies:** 2\ **Last updated:** [October 20, 2020, 12:26pm UTC](https://community.freefem.org/t/a-problem-of-stability/139 "2020-10-20T12:26:16Z")
Hi everyone, I write a program to simulate the cavity flow’s linear temporal growth rates and the neutral curve, but the results aren’t ideal, I put the program of linear temporal growth rates as flowing, looking … --- ## [How to get a matrix into Matlab](https://community.freefem.org/t/how-to-get-a-matrix-into-matlab/620)
**Author:** [@dajopez](https://community.freefem.org/u/dajopez)\ **Replies:** 2\ **Last updated:** [October 20, 2020, 12:19pm UTC](https://community.freefem.org/t/how-to-get-a-matrix-into-matlab/620 "2020-10-20T12:19:34Z")
Hello, I have a bunch of matrices calculated for a specific problem and want to put them into Matlab for data analysis. I can already see them in the log file, but I want the individual matrices saved as their own files… --- ## [Electron beam in electric field (ray-tracking)](https://community.freefem.org/t/electron-beam-in-electric-field-ray-tracking/612)
**Author:** [@atom1477](https://community.freefem.org/u/atom1477)\ **Replies:** 2\ **Last updated:** [October 20, 2020, 7:16am UTC](https://community.freefem.org/t/electron-beam-in-electric-field-ray-tracking/612 "2020-10-20T07:16:42Z")
Hello, I’m completely newbie in FF. I know that is possible to simulate electric field distribution using FF. But my question is, if it is an easy way to make one more additional step: Pass electron beam thru this si… [Previous page](https://community.freefem.org/c/general-discussion/7.md?page=65) [Next page](https://community.freefem.org/c/general-discussion/7.md?page=67)