# General Discussion **URL:** https://community.freefem.org/c/general-discussion/7.md?page=53 [Latest](https://community.freefem.org/latest.md) · [Categories](https://community.freefem.org/categories.md) **Page:** 54 --- ## [Non matching meshes](https://community.freefem.org/t/non-matching-meshes/1198)
**Author:** [@mrbenson](https://community.freefem.org/u/mrbenson)\ **Replies:** 2\ **Last updated:** [December 1, 2021, 6:00am UTC](https://community.freefem.org/t/non-matching-meshes/1198 "2021-12-01T06:00:23Z")
Hi, Is there a way to handle non-matching meshes (with no overlaps) with freefem. I have a very basic laplacian test case, two squares meshed independly but sharing a common boundary (same tag). I read that mortar metho… --- ## [RAM usage during parallel simulation](https://community.freefem.org/t/ram-usage-during-parallel-simulation/1357)
**Author:** [@marcodeba](https://community.freefem.org/u/marcodeba)\ **Replies:** 13\ **Last updated:** [November 30, 2021, 9:24am UTC](https://community.freefem.org/t/ram-usage-during-parallel-simulation/1357 "2021-11-30T09:24:09Z")
Dear FF users and developers, I’m writing here since I’m not properly understanding what’s happening to the RAM during the solution of a transient problem with PETSc. I have developed my code that is perfectly working,… --- ## [Optimized version](https://community.freefem.org/t/optimized-version/1358)
**Author:** [@Qianrui](https://community.freefem.org/u/Qianrui)\ **Replies:** 0\ **Last updated:** [November 28, 2021, 2:26am UTC](https://community.freefem.org/t/optimized-version/1358 "2021-11-28T02:26:04Z")
Hi, I also met the some problem for klein-gordon. --- ## [Unsteady Navier-Stokes Large Mesh](https://community.freefem.org/t/unsteady-navier-stokes-large-mesh/1018)
**Author:** [@Robert](https://community.freefem.org/u/Robert)\ **Replies:** 6\ **Last updated:** [November 28, 2021, 2:19am UTC](https://community.freefem.org/t/unsteady-navier-stokes-large-mesh/1018 "2021-11-28T02:19:39Z")
Hej, I am doing a mesh sensitivity analysis of an unsteady three-dimensional laminar flow. I am running the code in parallel with the preconditioner “-pc\_type lu”. Now I reached a mesh with ~200k nodes (~1 million eleme… --- ## [Error while using sparsesolver or UMFPACK](https://community.freefem.org/t/error-while-using-sparsesolver-or-umfpack/421)
**Author:** [@saptarshi](https://community.freefem.org/u/saptarshi)\ **Replies:** 5\ **Last updated:** [November 27, 2021, 1:35pm UTC](https://community.freefem.org/t/error-while-using-sparsesolver-or-umfpack/421 "2021-11-27T13:35:14Z")
Hello I am trying to solve a system using the Edge element and the variation form involves complex numbers . Some lines of the code : fespace Th( meshName , Edge13d ) … … … Th \< complex \> \[Ex,Ey,Ez\] ; … … … s… --- ## [Plot function does't work in a loop](https://community.freefem.org/t/plot-function-doest-work-in-a-loop/1356)
**Author:** [@lizemin5235](https://community.freefem.org/u/lizemin5235)\ **Replies:** 0\ **Last updated:** [November 27, 2021, 11:23am UTC](https://community.freefem.org/t/plot-function-doest-work-in-a-loop/1356 "2021-11-27T11:23:42Z")
I need to generate the train data used by the mechine learning, When I use random() function to build the vary domain, the output of the plot function does’t work, edp code is list as follow: int index =0; int NCount=1… --- ## [Time dependent Dirichlet BC](https://community.freefem.org/t/time-dependent-dirichlet-bc/987)
**Author:** [@adi\_luk](https://community.freefem.org/u/adi_luk)\ **Replies:** 6\ **Last updated:** [November 26, 2021, 10:45pm UTC](https://community.freefem.org/t/time-dependent-dirichlet-bc/987 "2021-11-26T22:45:12Z")
time\_dependent\_Dirichlet\_BC.edp (3.0 KB) Hello, i am new to FreeFem and i am trying to simulate the propagation of an acoustic wave generated by a transducer by solving the wave equation with a time dependent Dirichlet… --- ## [Define different regions and border in a 3D mesh](https://community.freefem.org/t/define-different-regions-and-border-in-a-3d-mesh/1341)
**Author:** [@ruffi92](https://community.freefem.org/u/ruffi92)\ **Replies:** 3\ **Last updated:** [November 26, 2021, 10:09pm UTC](https://community.freefem.org/t/define-different-regions-and-border-in-a-3d-mesh/1341 "2021-11-26T22:09:25Z")
Hi to all , i have problems to understand how to define a particular region inside a 3D mesh, and in particular how it works the definition of “labelmid” ecc… In detail, i have the following mesh: //Builds a mesh on 3d… --- ## [Remove all internal edges](https://community.freefem.org/t/remove-all-internal-edges/1353)
**Author:** [@Loic](https://community.freefem.org/u/Loic)\ **Replies:** 1\ **Last updated:** [November 26, 2021, 4:06pm UTC](https://community.freefem.org/t/remove-all-internal-edges/1353 "2021-11-26T16:06:37Z")
Hello all, How could I remove all internal edges from a meshed domain to keep only the border of the domain ? I have tried with the function change with "rmInternalEdges=true", but it does not work. Thank you in advan… --- ## [Streamline laplace equation](https://community.freefem.org/t/streamline-laplace-equation/833)
**Author:** [@mrbenson](https://community.freefem.org/u/mrbenson)\ **Replies:** 3\ **Last updated:** [November 26, 2021, 10:58am UTC](https://community.freefem.org/t/streamline-laplace-equation/833 "2021-11-26T10:58:16Z")
Hello, I’m back to compute streamlines function using the vorticity equation but it seems that something is wrong… It’s a very basic test case solving laplacian problem on a square. The streamlines are not parallel to … --- ## [Measure area only for specific labels](https://community.freefem.org/t/measure-area-only-for-specific-labels/1349)
**Author:** [@distractor](https://community.freefem.org/u/distractor)\ **Replies:** 2\ **Last updated:** [November 25, 2021, 6:12pm UTC](https://community.freefem.org/t/measure-area-only-for-specific-labels/1349 "2021-11-25T18:12:39Z")
So imagine a 3D body, can also be as simple as cube. load "msh3" int\[int\] l6 = \[37, 42, 45, 40, 25, 57\]; int r11 = 11; mesh3 Th = cube(4, 5, 6, \[x\*2-1, y\*2-1, z\*2-1\], label=l6, flags =3, region=r11); cout \<\< "Volume =… --- ## [Impose me value as boundary condition](https://community.freefem.org/t/impose-me-value-as-boundary-condition/1347)
**Author:** [@Loic](https://community.freefem.org/u/Loic)\ **Replies:** 1\ **Last updated:** [November 23, 2021, 1:53pm UTC](https://community.freefem.org/t/impose-me-value-as-boundary-condition/1347 "2021-11-23T13:53:54Z")
Hello, I want to impose the mean value of u as boundary condition. So I have tried to do this: on(1, int1d(Th,1)(u)=1), but it doesn’t work. Could someone face the same problem and help me ? Best regards, Loïc, --- ## [Is it possible to assign a pointer to a variable?](https://community.freefem.org/t/is-it-possible-to-assign-a-pointer-to-a-variable/1343)
**Author:** [@Markov](https://community.freefem.org/u/Markov)\ **Replies:** 11\ **Last updated:** [November 23, 2021, 11:57am UTC](https://community.freefem.org/t/is-it-possible-to-assign-a-pointer-to-a-variable/1343 "2021-11-23T11:57:27Z")
Hello, I was wondering if it is possible to assign a pointer to a variable like in C++ for instance, in order to access the value stored by this variable using (\*). --- ## [Cylinder sand column](https://community.freefem.org/t/cylinder-sand-column/1346)
**Author:** [@xiaojiemo](https://community.freefem.org/u/xiaojiemo)\ **Replies:** 0\ **Last updated:** [November 23, 2021, 6:37am UTC](https://community.freefem.org/t/cylinder-sand-column/1346 "2021-11-23T06:37:05Z")
hello,everyone, I am writing mesh code which is a column which is consisted of sand particle and water. I have finished the cylinder,which I still don’t have idea on how to generate the particles. maybe forming thounsan… --- ## [Rectangular Mat directly from varf](https://community.freefem.org/t/rectangular-mat-directly-from-varf/1344)
**Author:** [@aszaboa](https://community.freefem.org/u/aszaboa)\ **Replies:** 2\ **Last updated:** [November 22, 2021, 3:29pm UTC](https://community.freefem.org/t/rectangular-mat-directly-from-varf/1344 "2021-11-22T15:29:46Z")
Dear FreeFem users, I am trying to assemble a system from block matrices. Generally, one can create a Mat object and assign a value to it directly using the varf keyword. However, it does not seem to work for rectangula… --- ## [Applying pressure as boundary condition](https://community.freefem.org/t/applying-pressure-as-boundary-condition/1340)
**Author:** [@distractor](https://community.freefem.org/u/distractor)\ **Replies:** 0\ **Last updated:** [November 19, 2021, 5:42pm UTC](https://community.freefem.org/t/applying-pressure-as-boundary-condition/1340 "2021-11-19T17:42:14Z")
Hi, Let’s take the official elasticity example from here. Let’s remove the body force f and add another boundary condition at the right side (label = 2). This boundary condition is a pressure p that will elongate the be… --- ## [Normal to the boundary](https://community.freefem.org/t/normal-to-the-boundary/1339)
**Author:** [@zese](https://community.freefem.org/u/zese)\ **Replies:** 3\ **Last updated:** [November 19, 2021, 10:05am UTC](https://community.freefem.org/t/normal-to-the-boundary/1339 "2021-11-19T10:05:46Z")
Dear all, I want to specify a blowing on airfoil wall as v\_j=v.n\_w in which n\_w is the normal to the airfoil. How this normal can be defined?. Is N.y for normal to the boundary or it is just a unit vector in y direction… --- ## [Navier-Stokes periodic boundary conditions](https://community.freefem.org/t/navier-stokes-periodic-boundary-conditions/1327)
**Author:** [@msjolly57](https://community.freefem.org/u/msjolly57)\ **Replies:** 3\ **Last updated:** [November 19, 2021, 6:15am UTC](https://community.freefem.org/t/navier-stokes-periodic-boundary-conditions/1327 "2021-11-19T06:15:18Z")
Hello, I tried adapting the example NSE.edp in the FreeFem documentation to be fully periodic on the square. I get the error Problem build of FEspace (2d) (may be : due to periodic Boundary condition missing ) FH The… --- ## [Setting new border label by modifying the former border](https://community.freefem.org/t/setting-new-border-label-by-modifying-the-former-border/1335)
**Author:** [@zese](https://community.freefem.org/u/zese)\ **Replies:** 0\ **Last updated:** [November 18, 2021, 8:22am UTC](https://community.freefem.org/t/setting-new-border-label-by-modifying-the-former-border/1335 "2021-11-18T08:22:18Z")
Dear all I have an airfoil which I introduced as follow in FF++. now I want to specify some sluts on the airfoil and change the label. do you know how I can do that? real CC = 0.95105651629515357211643933337938; real … --- ## [Coupled PDEs with interface BCs](https://community.freefem.org/t/coupled-pdes-with-interface-bcs/1333)
**Author:** [@sumantkr](https://community.freefem.org/u/sumantkr)\ **Replies:** 0\ **Last updated:** [November 17, 2021, 4:49pm UTC](https://community.freefem.org/t/coupled-pdes-with-interface-bcs/1333 "2021-11-17T16:49:29Z")
Dear all I have gone for the interface boundary conditions example that is given in the domain decomposition. I have implemented this concept into coupled PDEs having two square subdomains with a conformal interface bo… --- ## [Unexpected result of electrostatic simulation](https://community.freefem.org/t/unexpected-result-of-electrostatic-simulation/1332)
**Author:** [@erbaun](https://community.freefem.org/u/erbaun)\ **Replies:** 0\ **Last updated:** [November 17, 2021, 4:29pm UTC](https://community.freefem.org/t/unexpected-result-of-electrostatic-simulation/1332 "2021-11-17T16:29:47Z")
Hello, I need to do some electrostatic simulations and decided to use FreeFEM for this. After successfully installing FreeFEM 4.10 from source on my Slackware Linux box, I started with the electrostatics example present… --- ## [Adjacent triangle](https://community.freefem.org/t/adjacent-triangle/1331)
**Author:** [@Amin](https://community.freefem.org/u/Amin)\ **Replies:** 0\ **Last updated:** [November 17, 2021, 9:08am UTC](https://community.freefem.org/t/adjacent-triangle/1331 "2021-11-17T09:08:50Z")
Hello, What is the difference between the two commands: Th\[1\].adj(0); and int e; Th\[1\].adj((e=0)) the latter works but the former does not. Thanks. --- ## [Adaptmesh bamg error](https://community.freefem.org/t/adaptmesh-bamg-error/773)
**Author:** [@mrbenson](https://community.freefem.org/u/mrbenson)\ **Replies:** 7\ **Last updated:** [November 16, 2021, 9:52am UTC](https://community.freefem.org/t/adaptmesh-bamg-error/773 "2021-11-16T09:52:15Z")
Hello, I get sometimes a fatal error in the mesh generator using adaptmesh with the following option iso=false, nbvx = 1e6, maxsubdiv=5 Is there an adaptmesh option for pervent this ? Best regards. number of require… --- ## [Parameters of mshmet](https://community.freefem.org/t/parameters-of-mshmet/1328)
**Author:** [@LucasPa](https://community.freefem.org/u/LucasPa)\ **Replies:** 2\ **Last updated:** [November 16, 2021, 8:35am UTC](https://community.freefem.org/t/parameters-of-mshmet/1328 "2021-11-16T08:35:19Z")
Hi all, This new post concerns the use of mshmet in FreeFem. My aim is to evaluate the use of mmg2d as I am now fully happy with the results obtained with adaptmesh. According to the FreeFem documentation, some paramet… --- ## [How to revise mesh using mshmet and mmg in 2d?](https://community.freefem.org/t/how-to-revise-mesh-using-mshmet-and-mmg-in-2d/1237)
**Author:** [@hezl09](https://community.freefem.org/u/hezl09)\ **Replies:** 1\ **Last updated:** [November 15, 2021, 3:18pm UTC](https://community.freefem.org/t/how-to-revise-mesh-using-mshmet-and-mmg-in-2d/1237 "2021-11-15T15:18:28Z")
Hi everyone, I have a question regarding the use of mshmet and mmg in FreeFEM++. I’m trying to revise my mesh so that its density gradually increases with the increase of x. Thus, I introduce a P1 variable G1 = x^2. + 0… --- ## [Transient problems in elasticity](https://community.freefem.org/t/transient-problems-in-elasticity/863)
**Author:** [@felric](https://community.freefem.org/u/felric)\ **Replies:** 6\ **Last updated:** [July 8, 2021, 2:26pm UTC](https://community.freefem.org/t/transient-problems-in-elasticity/863 "2021-07-08T14:26:33Z")
Dear all, first, many thanks for your wonderful software. I’m trying to solve transient problems in elasticity, more in particular simulation of mechanical resonators which have some damping (e.g. the time dependent re… --- ## [Exec error : exec assert](https://community.freefem.org/t/exec-error-exec-assert/1293)
**Author:** [@yongxing](https://community.freefem.org/u/yongxing)\ **Replies:** 33\ **Last updated:** [November 12, 2021, 10:14am UTC](https://community.freefem.org/t/exec-error-exec-assert/1293 "2021-11-12T10:14:12Z")
I run a piece of parallel code using 12 processors. This “Exec error” occurs randomly… what does this mean? --- ## [Bundling variables](https://community.freefem.org/t/bundling-variables/1319)
**Author:** [@smhosseini12](https://community.freefem.org/u/smhosseini12)\ **Replies:** 3\ **Last updated:** [November 11, 2021, 4:27pm UTC](https://community.freefem.org/t/bundling-variables/1319 "2021-11-11T16:27:54Z")
Hello all, Is there any way to bundle variables of different types in FreeFem++? Something like struct or class in C++ or MATLAB. Thanks in advance. --- ## ["Err border element not in mesh" importing 3D mesh from gmsh](https://community.freefem.org/t/err-border-element-not-in-mesh-importing-3d-mesh-from-gmsh/1317)
**Author:** [@ruffi92](https://community.freefem.org/u/ruffi92)\ **Replies:** 2\ **Last updated:** [November 11, 2021, 9:29am UTC](https://community.freefem.org/t/err-border-element-not-in-mesh-importing-3d-mesh-from-gmsh/1317 "2021-11-11T09:29:29Z")
Hi to all, i’m trying to import a 3D mesh .msh from gmsh 2.2 to FreeFem++ but i receive the following error: Loading packages… 916619 vertices closing file 5196967 4972572 5196967 tetrahedrons 4972572 triangles 1016… --- ## [Biharmonic problem with HCT element does not converge](https://community.freefem.org/t/biharmonic-problem-with-hct-element-does-not-converge/1314)
**Author:** [@viviaxenov](https://community.freefem.org/u/viviaxenov)\ **Replies:** 1\ **Last updated:** [November 9, 2021, 9:53am UTC](https://community.freefem.org/t/biharmonic-problem-with-hct-element-does-not-converge/1314 "2021-11-09T09:53:46Z")
I’ve been trying to solve the biharmonic problem Δu = f u = du/dn = 0 on the border I tried to verify it on some exact solution. I took the unit circle as the domain. The exact solution for verification was u(x, y) … [Previous page](https://community.freefem.org/c/general-discussion/7.md?page=52) [Next page](https://community.freefem.org/c/general-discussion/7.md?page=54)