# General Discussion **URL:** https://community.freefem.org/c/general-discussion/7.md?page=68 [Latest](https://community.freefem.org/latest.md) · [Categories](https://community.freefem.org/categories.md) **Page:** 69 --- ## [Can int0d deal with robin boundary condition?](https://community.freefem.org/t/can-int0d-deal-with-robin-boundary-condition/559)
**Author:** [@gero](https://community.freefem.org/u/gero)\ **Replies:** 4\ **Last updated:** [September 4, 2020, 9:46am UTC](https://community.freefem.org/t/can-int0d-deal-with-robin-boundary-condition/559 "2020-09-04T09:46:52Z")
Hi all, I am trying to use FreeFem++ for calculation of carburizing operations (steel heattreament). On a basic level these processes can be modelled as axisymmetric 1D. The attached code works with Dirichlet boundary… --- ## [Perform integrals in func](https://community.freefem.org/t/perform-integrals-in-func/563)
**Author:** [@nicoloabrate](https://community.freefem.org/u/nicoloabrate)\ **Replies:** 7\ **Last updated:** [September 3, 2020, 9:40am UTC](https://community.freefem.org/t/perform-integrals-in-func/563 "2020-09-03T09:40:50Z")
Dear FF developers, I would like to ask you how to correct the following error, 2 : { 3 : Vh w; 4 : w\[\] = u; 5 : real tI; 6 : tI = int2d(core) (w); 7 : cout\<\ **Author:** [@gero](https://community.freefem.org/u/gero)\ **Replies:** 0\ **Last updated:** [September 2, 2020, 5:54pm UTC](https://community.freefem.org/t/deal-with-diffusivity-as-function-of-concentration-and-temperature-in-diffusion-equation/565 "2020-09-02T17:54:41Z") Hi all, in case hardening simulation the diffusion coefficient of Carbon in Austenite Dc should depend on local Carbon concentration and Temperature: My first questionis: Is it really as easy as simply updating Dc in t… --- ## [Bloch boundary conditions](https://community.freefem.org/t/bloch-boundary-conditions/280)
**Author:** [@PhyzWiz](https://community.freefem.org/u/PhyzWiz)\ **Replies:** 1\ **Last updated:** [September 1, 2020, 4:07pm UTC](https://community.freefem.org/t/bloch-boundary-conditions/280 "2020-09-01T16:07:14Z")
Is there a way to implement Bloch (i.e. “twisted” periodic) boundary conditions in FreeFEM? --- ## [Simple integration question](https://community.freefem.org/t/simple-integration-question/558)
**Author:** [@dajopez](https://community.freefem.org/u/dajopez)\ **Replies:** 1\ **Last updated:** [August 31, 2020, 7:02am UTC](https://community.freefem.org/t/simple-integration-question/558 "2020-08-31T07:02:56Z")
Hello, I am trying to integrate the generated function over one of the borders of my domain, but I cannot figure out how. I tried cout \<\< int1d(border)(function) but int1d wants a mesh. To make a 1d mesh I believe I am… --- ## ["make check" failures on macOS](https://community.freefem.org/t/make-check-failures-on-macos/556)
**Author:** [@bpabbott](https://community.freefem.org/u/bpabbott)\ **Replies:** 5\ **Last updated:** [August 31, 2020, 6:23am UTC](https://community.freefem.org/t/make-check-failures-on-macos/556 "2020-08-31T06:23:15Z")
Running macOS 10.16.5 and the development branch. I see two failures. FAIL: LapComplexEigenValue.edp FAIL: LapnosymComplexEigenValue.edp Shall I copy the log my response, or is there a a preferred alternative? --- ## [Newton Method Convergence Error](https://community.freefem.org/t/newton-method-convergence-error/554)
**Author:** [@sumantkr](https://community.freefem.org/u/sumantkr)\ **Replies:** 0\ **Last updated:** [August 29, 2020, 10:26am UTC](https://community.freefem.org/t/newton-method-convergence-error/554 "2020-08-29T10:26:42Z")
Dear @frederichecht Sir, Based on the Steady NS Eqn, I am trying to solve a non-linear coupled equation. Unfortunately, my code is running but the relative error value is not decreasing after iteration. Sir, can you c… --- ## [Absolute value of real\[int,int\]](https://community.freefem.org/t/absolute-value-of-real-int-int/552)
**Author:** [@BeniaminBogosel](https://community.freefem.org/u/BeniaminBogosel)\ **Replies:** 1\ **Last updated:** [August 29, 2020, 7:24am UTC](https://community.freefem.org/t/absolute-value-of-real-int-int/552 "2020-08-29T07:24:32Z")
Hello, In the FreeFEM manual it is said that the function abs() should work on arrays of type real\[int,int\]. In practice, when I try to use it I get the error: Warning ambiguity Polymorphic Find 2. I have FreeFem 4.6 in… --- ## [Mesh generation](https://community.freefem.org/t/mesh-generation/551)
**Author:** [@mordechaiy](https://community.freefem.org/u/mordechaiy)\ **Replies:** 2\ **Last updated:** [August 27, 2020, 7:05pm UTC](https://community.freefem.org/t/mesh-generation/551 "2020-08-27T19:05:33Z")
Hello, I wanted to ask please, Is it possible in FreeFem++ to generate a uniform mesh while using the commands “border” and “buildmesh”? I looked at the FreeFem++ tutorial but, didn’t find an example. I know that t… --- ## [Maxwell related question](https://community.freefem.org/t/maxwell-related-question/548)
**Author:** [@fotios.kasolis](https://community.freefem.org/u/fotios.kasolis)\ **Replies:** 1\ **Last updated:** [August 24, 2020, 9:34am UTC](https://community.freefem.org/t/maxwell-related-question/548 "2020-08-24T09:34:55Z")
Dear all, I am trying to understand a bit more of FreeFEM’s type deduction strategy in the following case. If u is a P1 function, then grad(u) is an NE0 function, say in E1. If such a P1 function is known from solving a… --- ## [A Tutorial Introduction to FreeFEM](https://community.freefem.org/t/a-tutorial-introduction-to-freefem/539)
**Author:** [@fotios.kasolis](https://community.freefem.org/u/fotios.kasolis)\ **Replies:** 8\ **Last updated:** [August 22, 2020, 6:32am UTC](https://community.freefem.org/t/a-tutorial-introduction-to-freefem/539 "2020-08-22T06:32:20Z")
In https://github.com/fotios-kasolis/FreeFEM-tutorial-public you can find a hands-on FreeFEM tutorial. Although my initial plan was different, working time constraints force me to keep this work as an introduction to Fre… --- ## [Navier Stoke Operation Error](https://community.freefem.org/t/navier-stoke-operation-error/478)
**Author:** [@sumantkr](https://community.freefem.org/u/sumantkr)\ **Replies:** 6\ **Last updated:** [August 21, 2020, 12:59pm UTC](https://community.freefem.org/t/navier-stoke-operation-error/478 "2020-08-21T12:59:32Z")
Dear @prj I have taken a simple model for Navier Stoke Equation over a square. which I have taken from Navier-Stoke. I am getting an error as " operation error ". code is: real nu = 1.0/50.; real eps = 1e-6; verbo… --- ## [FEM Weak Form Help](https://community.freefem.org/t/fem-weak-form-help/541)
**Author:** [@sumantkr](https://community.freefem.org/u/sumantkr)\ **Replies:** 0\ **Last updated:** [August 19, 2020, 8:17am UTC](https://community.freefem.org/t/fem-weak-form-help/541 "2020-08-19T08:17:04Z")
Can anyone help me to get a weak form coding for equation: u\_x \* T\_y - u\_y \* T\_x = 0 ---------------------(1) The weak form as for test fn w is: w\_x \* u \* T\_y + w\_y \* u \* T\_x = 0 ---------------------------(2) And… --- ## [Conditions at the point](https://community.freefem.org/t/conditions-at-the-point/181)
**Author:** [@PoTS](https://community.freefem.org/u/PoTS)\ **Replies:** 5\ **Last updated:** [August 9, 2020, 4:31pm UTC](https://community.freefem.org/t/conditions-at-the-point/181 "2020-08-09T16:31:43Z")
Is it possible to provide additional condition for the solution of 2d problem at one point of the boundary (in FreeFem++)? Solution is a vector and the condition includes equality between one component and derivative of … --- ## [meshS for a Möbius strip](https://community.freefem.org/t/meshs-for-a-mobius-strip/536)
**Author:** [@julienG](https://community.freefem.org/u/julienG)\ **Replies:** 1\ **Last updated:** [August 9, 2020, 4:26pm UTC](https://community.freefem.org/t/meshs-for-a-mobius-strip/536 "2020-08-09T16:26:56Z")
Dear all, Is it possible to build a meshS for a Mobius strip? I am trying the following code mobius.edp (508 Bytes), with either movemesh23 or square3 functions. Both methods fail with similar error: Bad orientation:… --- ## [Global solution with PETSc](https://community.freefem.org/t/global-solution-with-petsc/239)
**Author:** [@henkel](https://community.freefem.org/u/henkel)\ **Replies:** 11\ **Last updated:** [August 7, 2020, 3:45pm UTC](https://community.freefem.org/t/global-solution-with-petsc/239 "2020-08-07T15:45:44Z")
For verification purposes I would like to compare a solution computed in parallel with the sequentially computed one. As a basis for an minimal working example I took an example from Pierre Jolivet’s tutorial and tried … --- ## [Need help in plotting graph of velocity (ux) vs time](https://community.freefem.org/t/need-help-in-plotting-graph-of-velocity-ux-vs-time/529)
**Author:** [@Rhushikesh](https://community.freefem.org/u/Rhushikesh)\ **Replies:** 3\ **Last updated:** [August 6, 2020, 10:17am UTC](https://community.freefem.org/t/need-help-in-plotting-graph-of-velocity-ux-vs-time/529 "2020-08-06T10:17:03Z")
/////////////////////////////////////////////////// /// UNSTEADY 2D NAVIER--STOKES //// /////////////////////////////////////////////////// ////////////////////////////////////////////////////////////… --- ## [A problem about adaptation](https://community.freefem.org/t/a-problem-about-adaptation/532)
**Author:** [@hai](https://community.freefem.org/u/hai)\ **Replies:** 0\ **Last updated:** [August 6, 2020, 4:20am UTC](https://community.freefem.org/t/a-problem-about-adaptation/532 "2020-08-06T04:20:49Z")
Dear all Recently I want to use an adaptive mesh to solve the equations to compare with the finite element results we have done before. However, there is a problem with adapation mesh.The plot adaptation mesh code is as… --- ## [Saving and loading global/distibuted arrays](https://community.freefem.org/t/saving-and-loading-global-distibuted-arrays/493)
**Author:** [@cmd](https://community.freefem.org/u/cmd)\ **Replies:** 39\ **Last updated:** [August 5, 2020, 8:24am UTC](https://community.freefem.org/t/saving-and-loading-global-distibuted-arrays/493 "2020-08-05T08:24:28Z")
Hello FreeFEM developers! Is there an easy way to gather/scatter distributed arrays on local partitions to/from a global array for file I/O under the HPDDM framework developed by @prj? In the examples I’ve seen (e.g. na… --- ## [Exporting Matrices of AS method for Poisson Equation](https://community.freefem.org/t/exporting-matrices-of-as-method-for-poisson-equation/526)
**Author:** [@gernot](https://community.freefem.org/u/gernot)\ **Replies:** 8\ **Last updated:** [July 31, 2020, 5:32pm UTC](https://community.freefem.org/t/exporting-matrices-of-as-method-for-poisson-equation/526 "2020-07-31T17:32:22Z")
I want to decompose a 3D mesh (sphere) into multiple subdomains and export the stiffness matrices / load vectors to solve the problem with an external CG solver. Unfortunately it seems that the local matrices are non-sy… --- ## [Static condensation for hybrid discontinuous Galerkin methods](https://community.freefem.org/t/static-condensation-for-hybrid-discontinuous-galerkin-methods/524)
**Author:** [@rochabm](https://community.freefem.org/u/rochabm)\ **Replies:** 6\ **Last updated:** [July 31, 2020, 5:23pm UTC](https://community.freefem.org/t/static-condensation-for-hybrid-discontinuous-galerkin-methods/524 "2020-07-31T17:23:21Z")
Hello everyone, I’ve been playing around with FF++ to solve some problems quite successfully. We are using a hybrid discontinuous Galerkin formulation. Currently, we are solving a time-dependent Cahn-Hilliard-like probl… --- ## [Number of degrees of freedom](https://community.freefem.org/t/number-of-degrees-of-freedom/523)
**Author:** [@hamed](https://community.freefem.org/u/hamed)\ **Replies:** 3\ **Last updated:** [July 30, 2020, 2:08pm UTC](https://community.freefem.org/t/number-of-degrees-of-freedom/523 "2020-07-30T14:08:29Z")
Dear all I like to limit my integration over a portion of whole. To do this I changed int2d(Th) to int2d(Th,Coil) varf vPoi(u,v) =int2d(Th,Coil) (sig \* Grad(u)' \* Grad(v)) +on(CoilTerminalIn, u=0) +on(Coil… --- ## [How to use Lagrange Multipliers in FreeFEM](https://community.freefem.org/t/how-to-use-lagrange-multipliers-in-freefem/514)
**Author:** [@kevinmo08](https://community.freefem.org/u/kevinmo08)\ **Replies:** 7\ **Last updated:** [July 29, 2020, 6:02am UTC](https://community.freefem.org/t/how-to-use-lagrange-multipliers-in-freefem/514 "2020-07-29T06:02:29Z")
Hi all, I am very new to the finite element field, and I want to try to solve the a variant of the fokker-plank equation with periodic boundary conditions. To do this, I need to find a way to impose an actual concentrat… --- ## [Manual modification of a mesh](https://community.freefem.org/t/manual-modification-of-a-mesh/522)
**Author:** [@paolopiers](https://community.freefem.org/u/paolopiers)\ **Replies:** 0\ **Last updated:** [July 26, 2020, 7:11pm UTC](https://community.freefem.org/t/manual-modification-of-a-mesh/522 "2020-07-26T19:11:14Z")
Hi everybody, I am working on a predictor-corrector algorithm in mechanics and I am stuck on the following technicality. The problem I am interested in is the following. Given a mesh (half a circle), I would like to m… --- ## [Inconsistency with mesh labels being recognized](https://community.freefem.org/t/inconsistency-with-mesh-labels-being-recognized/520)
**Author:** [@jgonzalez49](https://community.freefem.org/u/jgonzalez49)\ **Replies:** 1\ **Last updated:** [July 25, 2020, 5:34am UTC](https://community.freefem.org/t/inconsistency-with-mesh-labels-being-recognized/520 "2020-07-25T05:34:41Z")
I’m having an issue with the way a cube’s labels are being recognized in an example piece of code. In one example script, I group together the boundary conditions 1-6 and it works fine (though it doesn’t serve my need to… --- ## [Solving a lot of independent ODEs in parallel](https://community.freefem.org/t/solving-a-lot-of-independent-odes-in-parallel/518)
**Author:** [@david9333](https://community.freefem.org/u/david9333)\ **Replies:** 2\ **Last updated:** [July 23, 2020, 3:37pm UTC](https://community.freefem.org/t/solving-a-lot-of-independent-odes-in-parallel/518 "2020-07-23T15:37:49Z")
Hi! I am considering a time-dependent fluid-kinetic problem for which, at every time step, I have a PDE to solve (that’s ok, it takes 3 seconds and that is fine by me) and ODEs for 200 particles. In order to solve these… --- ## [How to implement Stress-Free BC](https://community.freefem.org/t/how-to-implement-stress-free-bc/516)
**Author:** [@Hanen](https://community.freefem.org/u/Hanen)\ **Replies:** 1\ **Last updated:** [July 23, 2020, 12:06pm UTC](https://community.freefem.org/t/how-to-implement-stress-free-bc/516 "2020-07-23T12:06:23Z")
Hello, I have a question about the implementation of stress free BC, actually i have a system of equations with 6 unknown (u1,u2…u6), i want to impose this BC on the u2 and u4. dn(u1)=-u2/(4\*r0) with dn the normal deri… --- ## [Non-linear Conjugate Gradient with DDM and PETSc](https://community.freefem.org/t/non-linear-conjugate-gradient-with-ddm-and-petsc/515)
**Author:** [@julienG](https://community.freefem.org/u/julienG)\ **Replies:** 2\ **Last updated:** [July 22, 2020, 8:43pm UTC](https://community.freefem.org/t/non-linear-conjugate-gradient-with-ddm-and-petsc/515 "2020-07-22T20:43:37Z")
Hi all, I have been interested in using a Non-Linear Conjugate Gradient (NLCG) method for minimizing non-linear problems and using DDM/PETSc tools. As discussed here, one can use for example TAO using the flags -tao\_typ… --- ## [How to plot solution of a 2D edp on a 1D line](https://community.freefem.org/t/how-to-plot-solution-of-a-2d-edp-on-a-1d-line/513)
**Author:** [@Trophime](https://community.freefem.org/u/Trophime)\ **Replies:** 2\ **Last updated:** [July 22, 2020, 6:47pm UTC](https://community.freefem.org/t/how-to-plot-solution-of-a-2d-edp-on-a-1d-line/513 "2020-07-22T18:47:47Z")
Hi, I would like to plot the solution of 2D edp on a line using for instance gnuplot. How can I get this done? More generally I would like to plot solution on a given contour. How can I define this contour and interp… --- ## [PDE of Schrodinger type](https://community.freefem.org/t/pde-of-schrodinger-type/512)
**Author:** [@PhyzWiz](https://community.freefem.org/u/PhyzWiz)\ **Replies:** 2\ **Last updated:** [July 21, 2020, 2:44pm UTC](https://community.freefem.org/t/pde-of-schrodinger-type/512 "2020-07-21T14:44:16Z")
Hello, I wish to solve a linear PDE of the form: -\\Delta u + V u = f in some 2d domain, where \\Delta is the Laplacian. In addition to f(x,y), there is now another function V(x,y), which is specified analytically. The … [Previous page](https://community.freefem.org/c/general-discussion/7.md?page=67) [Next page](https://community.freefem.org/c/general-discussion/7.md?page=69)