# General Discussion **URL:** https://community.freefem.org/c/general-discussion/7.md?page=71 [Latest](https://community.freefem.org/latest.md) · [Categories](https://community.freefem.org/categories.md) **Page:** 72 --- ## [Applying point displacement boundary condition](https://community.freefem.org/t/applying-point-displacement-boundary-condition/392)
**Author:** [@willkin](https://community.freefem.org/u/willkin)\ **Replies:** 0\ **Last updated:** [May 5, 2020, 8:01pm UTC](https://community.freefem.org/t/applying-point-displacement-boundary-condition/392 "2020-05-05T20:01:37Z")
I am looking for how to applying point displacement boundary conditions for elasticity bro. --- ## [Poisson equation for ions in the gas phase](https://community.freefem.org/t/poisson-equation-for-ions-in-the-gas-phase/387)
**Author:** [@val](https://community.freefem.org/u/val)\ **Replies:** 0\ **Last updated:** [May 4, 2020, 3:44pm UTC](https://community.freefem.org/t/poisson-equation-for-ions-in-the-gas-phase/387 "2020-05-04T15:44:06Z")
Hello Freefem community ! I am trying to solve a transport equation of ions in the gas phase between two circular electrode plates. There is a small radioactive source that produces ions in the space, both positives and… --- ## [Heat equation problem](https://community.freefem.org/t/heat-equation-problem/386)
**Author:** [@leopold](https://community.freefem.org/u/leopold)\ **Replies:** 0\ **Last updated:** [May 4, 2020, 12:56pm UTC](https://community.freefem.org/t/heat-equation-problem/386 "2020-05-04T12:56:06Z")
Hello, I am trying to solve the heat equation in a molten salt and in a metallic tank in 1D. The thickness of the system is equal to 7cm (2cm for the tank wall and 5cm for the salt). The salt has a residual power and in… --- ## [Are functions with general arguments possible?](https://community.freefem.org/t/are-functions-with-general-arguments-possible/383)
**Author:** [@amtravco](https://community.freefem.org/u/amtravco)\ **Replies:** 1\ **Last updated:** [May 3, 2020, 7:59am UTC](https://community.freefem.org/t/are-functions-with-general-arguments-possible/383 "2020-05-03T07:59:55Z")
Is there a way to write a function equivalent to f(a, b) = ax + by where a, b are local variables to the function and x, y, the built in current-point variables? Thus f(3, 5) would return 3x + 5y, with x, y having wha… --- ## [Adapmesh and heat equation](https://community.freefem.org/t/adapmesh-and-heat-equation/371)
**Author:** [@mrbenson](https://community.freefem.org/u/mrbenson)\ **Replies:** 2\ **Last updated:** [May 1, 2020, 6:21pm UTC](https://community.freefem.org/t/adapmesh-and-heat-equation/371 "2020-05-01T18:21:38Z")
Hello, I tried mesh adaptation procedure with a very simple heat equation and it seems something wrong with my basic heat problem. The geometry is a two layered wall junction and two Robin boundary conditions are prescr… --- ## [Load a large mesh](https://community.freefem.org/t/load-a-large-mesh/381)
**Author:** [@mrbenson](https://community.freefem.org/u/mrbenson)\ **Replies:** 0\ **Last updated:** [April 30, 2020, 5:49pm UTC](https://community.freefem.org/t/load-a-large-mesh/381 "2020-04-30T17:49:16Z")
(topic withdrawn by author, will be automatically deleted in 24 hours unless flagged) --- ## [Error assembling a matrix 3d surface mesh](https://community.freefem.org/t/error-assembling-a-matrix-3d-surface-mesh/325)
**Author:** [@Remi](https://community.freefem.org/u/Remi)\ **Replies:** 12\ **Last updated:** [April 27, 2020, 2:41pm UTC](https://community.freefem.org/t/error-assembling-a-matrix-3d-surface-mesh/325 "2020-04-27T14:41:18Z")
Hello, I came across a segmentation fault when trying to get a matrix from varf when using a 3d surface mesh. The following code gives the error, using the torus given as example in the doc. I have tried with both FreeF… --- ## [Non-penetration condition at solid wall](https://community.freefem.org/t/non-penetration-condition-at-solid-wall/369)
**Author:** [@Hong](https://community.freefem.org/u/Hong)\ **Replies:** 0\ **Last updated:** [April 24, 2020, 1:24am UTC](https://community.freefem.org/t/non-penetration-condition-at-solid-wall/369 "2020-04-24T01:24:21Z")
I impose a Navier slip boundary condition at an inclined wall to solve the liquid slip flow over hydrophobic surface. But the slip velocity penetrates into solid wall because uN.x + vN.y = 0 is not satisfied. How to impl… --- ## [How to use the solution of other eq. to import the boundary conditions?](https://community.freefem.org/t/how-to-use-the-solution-of-other-eq-to-import-the-boundary-conditions/365)
**Author:** [@Dylan](https://community.freefem.org/u/Dylan)\ **Replies:** 0\ **Last updated:** [April 22, 2020, 7:10am UTC](https://community.freefem.org/t/how-to-use-the-solution-of-other-eq-to-import-the-boundary-conditions/365 "2020-04-22T07:10:54Z")
Dear all, Example: I want to solve Stoke equation that the BC of horizontal velocity is related to stress. The stress data comes from the solution of another equation. How to use the solution of another eq. to import… --- ## [Multi-mesh discretization](https://community.freefem.org/t/multi-mesh-discretization/34)
**Author:** [@fanyuanhong](https://community.freefem.org/u/fanyuanhong)\ **Replies:** 1\ **Last updated:** [April 21, 2020, 10:02pm UTC](https://community.freefem.org/t/multi-mesh-discretization/34 "2020-04-21T22:02:37Z")
Hi guys, I want to know how to solve the below problem? My question is that if the computation domain is separated into several parts, like 3 parts, I want to use P1 on the 1rt part, P2 on the 2nd part and DG on the 3rd… --- ## [Mesh generation from a geometry](https://community.freefem.org/t/mesh-generation-from-a-geometry/362)
**Author:** [@mrbenson](https://community.freefem.org/u/mrbenson)\ **Replies:** 2\ **Last updated:** [April 21, 2020, 8:11pm UTC](https://community.freefem.org/t/mesh-generation-from-a-geometry/362 "2020-04-21T20:11:25Z")
Hi, Regarding the documentation it seems not possible to generate a mesh from a geometry model, as the geo gmsh file, directly in freefem ? PS : A geometry model is composed with : a list of vertices list of edges l… --- ## [Euclidean norm of a vector](https://community.freefem.org/t/euclidean-norm-of-a-vector/357)
**Author:** [@Biki](https://community.freefem.org/u/Biki)\ **Replies:** 1\ **Last updated:** [April 19, 2020, 5:43pm UTC](https://community.freefem.org/t/euclidean-norm-of-a-vector/357 "2020-04-19T17:43:41Z")
Hello! I’m so sorry to bother you but I’m new to FreeFEM and I have some trouble to solve this problem. I would like to plot in each point of the domain the intensity (i.e. |u|) of the displacement field u (solution of a… --- ## [Define plot range](https://community.freefem.org/t/define-plot-range/356)
**Author:** [@mrbenson](https://community.freefem.org/u/mrbenson)\ **Replies:** 0\ **Last updated:** [April 18, 2020, 9:49pm UTC](https://community.freefem.org/t/define-plot-range/356 "2020-04-18T21:49:49Z")
Hi, I’d like to display two functions in the same plot with fill=true, is there a way to define a specific range for each function ? Best regards. --- ## [Streamfunction for streamline](https://community.freefem.org/t/streamfunction-for-streamline/353)
**Author:** [@mrbenson](https://community.freefem.org/u/mrbenson)\ **Replies:** 2\ **Last updated:** [April 18, 2020, 8:09pm UTC](https://community.freefem.org/t/streamfunction-for-streamline/353 "2020-04-18T20:09:09Z")
Hi, I’d like to compute the scalar streamfunction of a given irrotational vector field. As mentioned in the documentation (p. 538) the streamfunction satifies a laplacian equation. I don’t know how to prescribe the rig… --- ## [Output value at domain](https://community.freefem.org/t/output-value-at-domain/355)
**Author:** [@sumantkr](https://community.freefem.org/u/sumantkr)\ **Replies:** 0\ **Last updated:** [April 18, 2020, 4:52pm UTC](https://community.freefem.org/t/output-value-at-domain/355 "2020-04-18T16:52:18Z")
How to find the value of the output variable at equispaced domain point and boundary points. Like points are placed at equal spaced uniformly in a unit rectangle. I want to get the value of u at these points. --- ## [Paraview - incorporate solution computed for a certain mesh in a transformation of the same mesh](https://community.freefem.org/t/paraview-incorporate-solution-computed-for-a-certain-mesh-in-a-transformation-of-the-same-mesh/344)
**Author:** [@paolopiers](https://community.freefem.org/u/paolopiers)\ **Replies:** 11\ **Last updated:** [April 18, 2020, 8:28am UTC](https://community.freefem.org/t/paraview-incorporate-solution-computed-for-a-certain-mesh-in-a-transformation-of-the-same-mesh/344 "2020-04-18T08:28:40Z")
Dear Community Members, I would like to ask for your help in merit to a recent problem I run up against. I am trying to solve a boundary value problem defined over the square \[0,pi\] x \[0,H\], where H\>0. To define such … --- ## [Exterior \*and\* interior boundary?](https://community.freefem.org/t/exterior-and-interior-boundary/351)
**Author:** [@amtravco](https://community.freefem.org/u/amtravco)\ **Replies:** 0\ **Last updated:** [April 16, 2020, 1:57am UTC](https://community.freefem.org/t/exterior-and-interior-boundary/351 "2020-04-16T01:57:22Z")
I’m modeling a superconductor using the London equation ∇^2 A - A/λ^2 = 0, where A is the vector potential (a vector in 2D or 3D space) and λ is a constant. In the superconductor λ ≠ 0, while outside it λ = 0. In the us… --- ## [Plot of diplacement field](https://community.freefem.org/t/plot-of-diplacement-field/347)
**Author:** [@Biki](https://community.freefem.org/u/Biki)\ **Replies:** 2\ **Last updated:** [April 15, 2020, 1:07pm UTC](https://community.freefem.org/t/plot-of-diplacement-field/347 "2020-04-15T13:07:50Z")
Hi! I’ll try to explain my problem as briefly as possible. The setting is this: fespace Vh(Th,\[P1,P1\]); macro u \[u0,u1\] // Vh u; I find the displacement u as a solution of an elasticity problem. I’ve done the followi… --- ## [Fespace boundary sort](https://community.freefem.org/t/fespace-boundary-sort/342)
**Author:** [@amina](https://community.freefem.org/u/amina)\ **Replies:** 1\ **Last updated:** [April 13, 2020, 7:15pm UTC](https://community.freefem.org/t/fespace-boundary-sort/342 "2020-04-13T19:15:20Z")
Dear all, Can anyone enlighten me on the relationship between the mesh connectivity and the fespace connectivity? I actually rearranged my mesh nodes on the boundaries to make sure they’re in ascending order with regar… --- ## [Evolution problem error](https://community.freefem.org/t/evolution-problem-error/339)
**Author:** [@sumantkr](https://community.freefem.org/u/sumantkr)\ **Replies:** 9\ **Last updated:** [April 12, 2020, 5:49pm UTC](https://community.freefem.org/t/evolution-problem-error/339 "2020-04-12T17:49:14Z")
Dear All, I am trying to solve transient problem for porous media. Unfortunately, the time-dependent function is not updating after time increment, which gives us an undesired output value. Kindly suggest, where it we… --- ## [Connectivity: mesh vs. fespace](https://community.freefem.org/t/connectivity-mesh-vs-fespace/292)
**Author:** [@amina](https://community.freefem.org/u/amina)\ **Replies:** 1\ **Last updated:** [April 10, 2020, 3:17pm UTC](https://community.freefem.org/t/connectivity-mesh-vs-fespace/292 "2020-04-10T15:17:55Z")
Dear all, I was trying to rearrange my boundary nodes is ascending order and I succeeded in doing it using Th1 = change(Th1, renumv=new2old); However, I figured out that the FEM space connectivity is not the same as t… --- ## [Transformations and FEM space](https://community.freefem.org/t/transformations-and-fem-space/320)
**Author:** [@amina](https://community.freefem.org/u/amina)\ **Replies:** 4\ **Last updated:** [April 9, 2020, 11:10pm UTC](https://community.freefem.org/t/transformations-and-fem-space/320 "2020-04-09T23:10:15Z")
Hi all, I would like to create an interpolation matrix between two finite element spaces associated to the same mesh, but the geometry is transformed (rotated and translated). Actually, the connectivity at the FE space… --- ## [Exec error op\_readKN](https://community.freefem.org/t/exec-error-op-readkn/321)
**Author:** [@littleprg](https://community.freefem.org/u/littleprg)\ **Replies:** 1\ **Last updated:** [April 8, 2020, 6:04am UTC](https://community.freefem.org/t/exec-error-op-readkn/321 "2020-04-08T06:04:08Z")
Hello everybody. I’m new at using freefem and I started using a code which may have to work of a simulation of a mechanical problem. Running the code I repeatedly got this exec error: Fatal error in op\_readKN(array) C… --- ## [Gmsh: Error reading the mesh](https://community.freefem.org/t/gmsh-error-reading-the-mesh/317)
**Author:** [@Julien](https://community.freefem.org/u/Julien)\ **Replies:** 1\ **Last updated:** [April 3, 2020, 4:34pm UTC](https://community.freefem.org/t/gmsh-error-reading-the-mesh/317 "2020-04-03T16:34:03Z")
Hi everyone ! I have an error reading a simple Gmsh mesh in FreeFem++ #FreeFem ++ ouput: Element of type 3 is not considered in Freefem++ #FreeFem++ script: load “gmsh” mesh Th = gmshload(“square.msh”); #Gmsh .geo… --- ## [Building a .msh file with Matlab](https://community.freefem.org/t/building-a-msh-file-with-matlab/312)
**Author:** [@ppeterson75](https://community.freefem.org/u/ppeterson75)\ **Replies:** 2\ **Last updated:** [March 30, 2020, 10:11am UTC](https://community.freefem.org/t/building-a-msh-file-with-matlab/312 "2020-03-30T10:11:00Z")
Hello, I’m trying to build a volume mesh starting from points on a surface. The points are calculated by surface\_evolver, a free tool for fluidic calculations, and lie on the upper surface of a drop. To build a solid … --- ## [Thermoelastic axisymmetric problem](https://community.freefem.org/t/thermoelastic-axisymmetric-problem/314)
**Author:** [@ronic](https://community.freefem.org/u/ronic)\ **Replies:** 1\ **Last updated:** [March 27, 2020, 5:32pm UTC](https://community.freefem.org/t/thermoelastic-axisymmetric-problem/314 "2020-03-27T17:32:18Z")
Dear All, I still try to solve a circular mirror deformation (in steady state) heated by a laser beam in its center. First, I solve the temperature axisymmetric problem (with radiation) similar to the freefem documenta… --- ## [Recursion in FreeFem](https://community.freefem.org/t/recursion-in-freefem/313)
**Author:** [@Ancylutis](https://community.freefem.org/u/Ancylutis)\ **Replies:** 4\ **Last updated:** [March 27, 2020, 5:08pm UTC](https://community.freefem.org/t/recursion-in-freefem/313 "2020-03-27T17:08:06Z")
Hello, I would like to know if it is possible to do recursive function in FreeFem? Because when I try to do recursion I get “Identifier \ does not exist” error. Thanks in advance for your… --- ## [Curl in cylindrical coordinate](https://community.freefem.org/t/curl-in-cylindrical-coordinate/305)
**Author:** [@marcodeba](https://community.freefem.org/u/marcodeba)\ **Replies:** 3\ **Last updated:** [March 27, 2020, 1:12pm UTC](https://community.freefem.org/t/curl-in-cylindrical-coordinate/305 "2020-03-27T13:12:16Z")
Hi everybody! I need to perform some magnetostatic analysis in geometries that are actually close to a solenoid. I’m producing the mesh in 2D, due to the Axial symmetry of the problem and, using the A-formulation of th… --- ## [Border conditions wih thermo-elastic problem](https://community.freefem.org/t/border-conditions-wih-thermo-elastic-problem/309)
**Author:** [@ronic](https://community.freefem.org/u/ronic)\ **Replies:** 2\ **Last updated:** [March 27, 2020, 11:36am UTC](https://community.freefem.org/t/border-conditions-wih-thermo-elastic-problem/309 "2020-03-27T11:36:46Z")
Dear All, I’m a beginner in using freefem and finite elements computation and I need help to better understand in particular border conditions. I’m modeling a circular mirror in vacuum, held in his mount by the rear su… --- ## [Is the command "Th(x,y,z).region" available for surface meshes?](https://community.freefem.org/t/is-the-command-th-x-y-z-region-available-for-surface-meshes/306)
**Author:** [@Remi](https://community.freefem.org/u/Remi)\ **Replies:** 2\ **Last updated:** [March 25, 2020, 2:42pm UTC](https://community.freefem.org/t/is-the-command-th-x-y-z-region-available-for-surface-meshes/306 "2020-03-25T14:42:48Z")
Hi. I have a surface mesh, generated with GMSH, on which I have defined different regions/physical surfaces. What I would like to do is to get a point’s region’s tag. I tried Th(x,y,z).region and Th(x,y,z).label but bot… [Previous page](https://community.freefem.org/c/general-discussion/7.md?page=70) [Next page](https://community.freefem.org/c/general-discussion/7.md?page=72)