# General Discussion **URL:** https://community.freefem.org/c/general-discussion/7.md?page=47 [Latest](https://community.freefem.org/latest.md) · [Categories](https://community.freefem.org/categories.md) **Page:** 48 --- ## [Having a Jump BC for a continuous element type](https://community.freefem.org/t/having-a-jump-bc-for-a-continuous-element-type/1673)
**Author:** [@mahdi](https://community.freefem.org/u/mahdi)\ **Replies:** 2\ **Last updated:** [April 28, 2022, 8:20am UTC](https://community.freefem.org/t/having-a-jump-bc-for-a-continuous-element-type/1673 "2022-04-28T08:20:19Z")
Dear colleagues; Is it possible to have a jump over an edge for a continuous element type? Based on my smattering, it should work for p0, p1dc, p2dc, … However, the example in the document has done it for a p1 element. … --- ## [Periodic FE space in parallel computation (PETSc)](https://community.freefem.org/t/periodic-fe-space-in-parallel-computation-petsc/1652)
**Author:** [@marcodeba](https://community.freefem.org/u/marcodeba)\ **Replies:** 16\ **Last updated:** [April 28, 2022, 8:05am UTC](https://community.freefem.org/t/periodic-fe-space-in-parallel-computation-petsc/1652 "2022-04-28T08:05:04Z")
Dear FreeFem developers and users, I’m writing since I’m facing a trouble conncected with the definition of periodic finite element spaces in case of parallel computations. I am just trying to define a very simple peri… --- ## [Three dimensional anisotropic mesh adaptive](https://community.freefem.org/t/three-dimensional-anisotropic-mesh-adaptive/1657)
**Author:** [@wanglongfei](https://community.freefem.org/u/wanglongfei)\ **Replies:** 3\ **Last updated:** [April 28, 2022, 1:23am UTC](https://community.freefem.org/t/three-dimensional-anisotropic-mesh-adaptive/1657 "2022-04-28T01:23:33Z")
hello Sorry to bother you, recently, I tried to use Mshmet and MMG3D to generate three-dimensional anisotropic mesh, but the generated mesh anisotropy is not strong, that is, the mesh ratio is not very large, for exampl… --- ## [Writing a constraint for a jump](https://community.freefem.org/t/writing-a-constraint-for-a-jump/1694)
**Author:** [@mahdi](https://community.freefem.org/u/mahdi)\ **Replies:** 1\ **Last updated:** [April 25, 2022, 10:44pm UTC](https://community.freefem.org/t/writing-a-constraint-for-a-jump/1694 "2022-04-25T22:44:33Z")
Dear colleagues; I have trouble creating a jump over an edge for my field, \\psi, a P2 element. I am solving, where q and \\mu are known, and r is a multiplier: Over a square, with an extracted circle from the center … --- ## [Visulization of xy plot](https://community.freefem.org/t/visulization-of-xy-plot/1699)
**Author:** [@zese](https://community.freefem.org/u/zese)\ **Replies:** 0\ **Last updated:** [April 26, 2022, 11:34am UTC](https://community.freefem.org/t/visulization-of-xy-plot/1699 "2022-04-26T11:34:53Z")
Dear all, I want to plot a xy graph through solving and update it. for example the velocity in a point through time to see if it is converged or not (periodic). I tried using the following real\[int\] xx(2), yy(2); for … --- ## [OpenFOAM Solution to FreeFEM Solution Interpolation](https://community.freefem.org/t/openfoam-solution-to-freefem-solution-interpolation/1691)
**Author:** [@D\_N\_Sarkar](https://community.freefem.org/u/D_N_Sarkar)\ **Replies:** 2\ **Last updated:** [April 22, 2022, 7:56am UTC](https://community.freefem.org/t/openfoam-solution-to-freefem-solution-interpolation/1691 "2022-04-22T07:56:57Z")
I have a flow field solution that has been computed in OpenFOAM. But I would like to interpolate the solution to FreeFEM. What is the method/process to carry out this interpolation on FreeFEM mesh? --- ## [How to select a field in a specific area?](https://community.freefem.org/t/how-to-select-a-field-in-a-specific-area/1659)
**Author:** [@chalmi](https://community.freefem.org/u/chalmi)\ **Replies:** 1\ **Last updated:** [April 21, 2022, 6:26am UTC](https://community.freefem.org/t/how-to-select-a-field-in-a-specific-area/1659 "2022-04-21T06:26:30Z")
Hi everyone, I’m new here, and I need some help. I’m working on CSI (contrast source inversion method) which is an inverse scattering problem. In this method, I have to solve EDP this is why I use Freefem++. My domain i… --- ## [Savevtk() for 3D curve data](https://community.freefem.org/t/savevtk-for-3d-curve-data/1687)
**Author:** [@yongxing](https://community.freefem.org/u/yongxing)\ **Replies:** 0\ **Last updated:** [April 20, 2022, 3:53pm UTC](https://community.freefem.org/t/savevtk-for-3d-curve-data/1687 "2022-04-20T15:53:05Z")
It seems that savevtk() does NOT work for 1D data. Is there an alternative method to save 1D data for paraview? --- ## [Second order dxx, solver crash](https://community.freefem.org/t/second-order-dxx-solver-crash/1635)
**Author:** [@tess35](https://community.freefem.org/u/tess35)\ **Replies:** 4\ **Last updated:** [April 19, 2022, 8:46pm UTC](https://community.freefem.org/t/second-order-dxx-solver-crash/1635 "2022-04-19T20:46:13Z")
Hi everybody, I have a difficulty with the second order dxx(). Take a simple model, u’’’(x)=1 \<=\> int2d u’’(x)v(x)=int2d 6v(x). The solution is polynomial of degree 3, like x^3 + constant mesh Th=square(100… --- ## [Basic Query regarding function spaces](https://community.freefem.org/t/basic-query-regarding-function-spaces/1675)
**Author:** [@aparna](https://community.freefem.org/u/aparna)\ **Replies:** 3\ **Last updated:** [April 18, 2022, 2:57pm UTC](https://community.freefem.org/t/basic-query-regarding-function-spaces/1675 "2022-04-18T14:57:32Z")
How we can write function space for tensor valued function ? how we can write exact solution if it is a vector ? func f = \[-2pi^3cos(piy)sin(piy)(2cos(2pix) - 1), 2pi^3sin(pix)cos(pix)(2cos(2piy) - 1)\]; This is correc… --- ## [How to calculate Euler-Lagrange equations in the linear elasticity equation?](https://community.freefem.org/t/how-to-calculate-euler-lagrange-equations-in-the-linear-elasticity-equation/1678)
**Author:** [@sosome](https://community.freefem.org/u/sosome)\ **Replies:** 1\ **Last updated:** [April 18, 2022, 8:49am UTC](https://community.freefem.org/t/how-to-calculate-euler-lagrange-equations-in-the-linear-elasticity-equation/1678 "2022-04-18T08:49:07Z")
Dear all, I am trying to euler-lagrange equation in the linear elasticity equation, but I don’t know how to calculate energy form. σ = stress, ε = strain, Ω = boundary, Γ = domain geometry //Parameters real Rho = 80… --- ## [High-pressure gas tank](https://community.freefem.org/t/high-pressure-gas-tank/1669)
**Author:** [@fgomm](https://community.freefem.org/u/fgomm)\ **Replies:** 1\ **Last updated:** [April 18, 2022, 8:38am UTC](https://community.freefem.org/t/high-pressure-gas-tank/1669 "2022-04-18T08:38:06Z")
Hi, full disclosure: I have not yet tried FreeFEM. I do have some experience with Abaqus CAE. Just wondering before getting all in, is it possible for FreeFEM to simulate the wall stresses of a pressure vessel as functio… --- ## ["Jump" boundary condition, or a Periodic Boundary Condition with offset](https://community.freefem.org/t/jump-boundary-condition-or-a-periodic-boundary-condition-with-offset/932)
**Author:** [@kevinmo08](https://community.freefem.org/u/kevinmo08)\ **Replies:** 1\ **Last updated:** [April 15, 2022, 7:20pm UTC](https://community.freefem.org/t/jump-boundary-condition-or-a-periodic-boundary-condition-with-offset/932 "2022-04-15T19:20:55Z")
Hi all, I am interested in solving the Laplace equation with a particular set of boundary conditions. Normal periodic boundaries impose u at Border A = u at Border B. I want to impose u @ Border A = u @ Border B + 1 … --- ## [SLEPc different values with -np 1 vs -np 2+](https://community.freefem.org/t/slepc-different-values-with-np-1-vs-np-2/1663)
**Author:** [@Robert](https://community.freefem.org/u/Robert)\ **Replies:** 6\ **Last updated:** [April 13, 2022, 5:07pm UTC](https://community.freefem.org/t/slepc-different-values-with-np-1-vs-np-2/1663 "2022-04-13T17:07:27Z")
Dear forum, I am using FreeFEM++ v4.8 for Windows to perform a stability analysis with the SLEPc library. If I set -np 1 and I repeat the simulations without changing anything else I get everytime the same results. When… --- ## [Segmentation error with fine mesh](https://community.freefem.org/t/segmentation-error-with-fine-mesh/1668)
**Author:** [@Loic](https://community.freefem.org/u/Loic)\ **Replies:** 4\ **Last updated:** [April 13, 2022, 3:15pm UTC](https://community.freefem.org/t/segmentation-error-with-fine-mesh/1668 "2022-04-13T15:15:13Z")
Plane\_5.zip (5.7 KB) Hello all, I have the following mesh. When I try to open it like this: mesh Th1=gmshload("Plane\_5.msh"); I get the following errror: Assertion fail : (area \> 0) line :303, in file ../seq/includ… --- ## [Problems computing Eigenvalues in adaptive mesh refinement](https://community.freefem.org/t/problems-computing-eigenvalues-in-adaptive-mesh-refinement/1666)
**Author:** [@Curiin](https://community.freefem.org/u/Curiin)\ **Replies:** 0\ **Last updated:** [April 13, 2022, 11:38am UTC](https://community.freefem.org/t/problems-computing-eigenvalues-in-adaptive-mesh-refinement/1666 "2022-04-13T11:38:44Z")
Hi everyone I am trying to solve the generalised Laplace problem with Dirichlet boundary conditions on an annulus and refine the mesh adaptively. To do so, I used chapter 5.1.9 “Adaptation using residual error indicato… --- ## [How to find the largest element in the stiffness matrix？](https://community.freefem.org/t/how-to-find-the-largest-element-in-the-stiffness-matrix/1665)
**Author:** [@Qianrui](https://community.freefem.org/u/Qianrui)\ **Replies:** 0\ **Last updated:** [April 13, 2022, 5:40am UTC](https://community.freefem.org/t/how-to-find-the-largest-element-in-the-stiffness-matrix/1665 "2022-04-13T05:40:13Z")
matrix B=rhs1(Xh,Xh); --- ## [Structured Triangular Type of Mesh of "T" section](https://community.freefem.org/t/structured-triangular-type-of-mesh-of-t-section/1661)
**Author:** [@D\_N\_Sarkar](https://community.freefem.org/u/D_N_Sarkar)\ **Replies:** 3\ **Last updated:** [April 13, 2022, 3:49am UTC](https://community.freefem.org/t/structured-triangular-type-of-mesh-of-t-section/1661 "2022-04-13T03:49:21Z")
I would like to mesh a “T” type of geometry as follows: How can I mesh it using structured triangular type of mesh? Can the command “square” be used to mesh the above “T” type of geometry? --- ## [Petsc direct solvers](https://community.freefem.org/t/petsc-direct-solvers/1664)
**Author:** [@mrbenson](https://community.freefem.org/u/mrbenson)\ **Replies:** 1\ **Last updated:** [April 12, 2022, 6:24pm UTC](https://community.freefem.org/t/petsc-direct-solvers/1664 "2022-04-12T18:24:05Z")
Hello, Using petsc module, how can I be sure about the solver among mumps or pardiso ? It’s not very clear since I don’t import mumps modules, which solver is user by default ? Thanks for the explanation. --- ## [Strange behaviour with int2d (Freefem 4.10)](https://community.freefem.org/t/strange-behaviour-with-int2d-freefem-4-10/1662)
**Author:** [@Trophime](https://community.freefem.org/u/Trophime)\ **Replies:** 2\ **Last updated:** [April 12, 2022, 11:01am UTC](https://community.freefem.org/t/strange-behaviour-with-int2d-freefem-4-10/1662 "2022-04-12T11:01:22Z")
Hi, I’ve defined a Th mesh with a region Coil1. func Pk = P1; fespace Ah(Th, Pk); Ah Coil = 1\*(Th(x,y).region == Coil1); real Area = int2d(Th, qforder=6)(Coil); real Area1 = int2d(Th, qforder=6)(1\*(Th(x,y).region == C… --- ## [How to properly defined element of PkEdge](https://community.freefem.org/t/how-to-properly-defined-element-of-pkedge/1660)
**Author:** [@Trophime](https://community.freefem.org/u/Trophime)\ **Replies:** 1\ **Last updated:** [April 12, 2022, 10:37am UTC](https://community.freefem.org/t/how-to-properly-defined-element-of-pkedge/1660 "2022-04-12T10:37:41Z")
Hi, I’m trying to implement maxwell equations in 2D using the so called H model in H(curl). I cannot figure out how to declare the components of the vectorial field. I’ve naively tried: func Pk = P1edge; fespace Ah(Th,… --- ## [Solving Non-homogeneous Neumann BVP](https://community.freefem.org/t/solving-non-homogeneous-neumann-bvp/1654)
**Author:** [@asif.omi](https://community.freefem.org/u/asif.omi)\ **Replies:** 5\ **Last updated:** [April 11, 2022, 8:30am UTC](https://community.freefem.org/t/solving-non-homogeneous-neumann-bvp/1654 "2022-04-11T08:30:32Z")
Dear experts, Can you guide me how to implement this in FreeFem++ ? Many many thanks in advance. --- ## [Compressibility assumption not respected](https://community.freefem.org/t/compressibility-assumption-not-respected/1653)
**Author:** [@mchetoui](https://community.freefem.org/u/mchetoui)\ **Replies:** 3\ **Last updated:** [April 8, 2022, 3:57pm UTC](https://community.freefem.org/t/compressibility-assumption-not-respected/1653 "2022-04-08T15:57:29Z")
Hello everyone, I’m trying to simulate a 2D fluid flow in two adjacent rectangular regions separated with a border: a free flow region (Stokes) and a porous region (Darcy). The inlet and the outlet are defined in the S… --- ## [The law of triangulation of unit disk](https://community.freefem.org/t/the-law-of-triangulation-of-unit-disk/1651)
**Author:** [@Qianrui](https://community.freefem.org/u/Qianrui)\ **Replies:** 3\ **Last updated:** [April 8, 2022, 3:23pm UTC](https://community.freefem.org/t/the-law-of-triangulation-of-unit-disk/1651 "2022-04-08T15:23:32Z")
The triangulation of unit disk is not consistent with that of rectangular area, for example mesh Th=square(64,64,\[-4+8x,-4+8y\]), the spatial step size is 8/64=1/8, So the error convergence order is log(errorh)… --- ## [Integral in parallel](https://community.freefem.org/t/integral-in-parallel/1649)
**Author:** [@etj](https://community.freefem.org/u/etj)\ **Replies:** 4\ **Last updated:** [April 7, 2022, 7:26am UTC](https://community.freefem.org/t/integral-in-parallel/1649 "2022-04-07T07:26:53Z")
Hello, When computing an integral in parallel, I know one needs to scale things and do a global reduction. There are examples in previous posts (for example here) with the integral of 2 vectors, say: Vh\ scaled… --- ## [In optimized version](https://community.freefem.org/t/in-optimized-version/1650)
**Author:** [@Qianrui](https://community.freefem.org/u/Qianrui)\ **Replies:** 0\ **Last updated:** [April 6, 2022, 12:13pm UTC](https://community.freefem.org/t/in-optimized-version/1650 "2022-04-06T12:13:17Z")
In the process of time cycling, if the total time is T=0.5 and the number of cycles is KK=128, when the cycle reaches KK=50, what happens is the following situation. Why? --- ## [Adding/loading new Finite element](https://community.freefem.org/t/adding-loading-new-finite-element/1604)
**Author:** [@Carina](https://community.freefem.org/u/Carina)\ **Replies:** 4\ **Last updated:** [April 6, 2022, 10:33am UTC](https://community.freefem.org/t/adding-loading-new-finite-element/1604 "2022-04-06T10:33:12Z")
Hi, I am trying to implement a new finite Element. But I actually don’t get how to load this with the dynamical link. I already read the documentation a couple of times and I am using windows. The example load.edp works… --- ## [Install FreeFem on cluster](https://community.freefem.org/t/install-freefem-on-cluster/1645)
**Author:** [@yhao](https://community.freefem.org/u/yhao)\ **Replies:** 2\ **Last updated:** [April 5, 2022, 2:12pm UTC](https://community.freefem.org/t/install-freefem-on-cluster/1645 "2022-04-05T14:12:08Z")
Hi, I am trying to install freefem on a cluster but I always meet an error when compiling petsc. It always says there are two errors then the compilation stopped. The error message is like this: \[gmakefile:188: arch… --- ## [3D case,label of triangles, not tetrahedra](https://community.freefem.org/t/3d-case-label-of-triangles-not-tetrahedra/1640)
**Author:** [@DongweiYe](https://community.freefem.org/u/DongweiYe)\ **Replies:** 2\ **Last updated:** [April 5, 2022, 12:23pm UTC](https://community.freefem.org/t/3d-case-label-of-triangles-not-tetrahedra/1640 "2022-04-05T12:23:40Z")
Hi everyone, I am a new user of Freefem. I have a question about getting the labels of triangles from a 3D mesh. The situation is like this, I have a 3D mesh generated by Gmsh and save it as .mesh format. In the mesh, I… --- ## [Storing data for each timestep](https://community.freefem.org/t/storing-data-for-each-timestep/1647)
**Author:** [@zese](https://community.freefem.org/u/zese)\ **Replies:** 1\ **Last updated:** [April 5, 2022, 11:54am UTC](https://community.freefem.org/t/storing-data-for-each-timestep/1647 "2022-04-05T11:54:07Z")
Dear all I solve unsteady navier-stokes equation in FF++ and I want to store velocities (u,v) in a matrix for one period and for each time step. is there anyway to write it? For instance, for (i=0; i\