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From: | Renard Yves |
Subject: | Re: [Getfem-users] Lineic boundary conditions |
Date: | Tue, 01 Jun 2010 20:09:49 +0200 |
User-agent: | Dynamic Internet Messaging Program (DIMP) H3 (1.1.2) |
Dear Jean-Francois,Yes, the problem is that integration method in getfem are defined on the element and the boundary of the element not in n-2 dimension structures. If you have a mean to define an integration method on this polyline, then you can assemble your Neumann term. But the only mean, for the moment, to define a 1D integration method on a 3D domain is to define some 1D elements. The problem if you do so is that this integration method will only be defined on the 1D elements, not a the 3D elements on which you want to integrate. So, I think, the only mean which exists right now is to use an interpolation of the 3D fem on the 1D elements and assemble the term. (see interpolation of a fem) It is rather tricky for such a simple operation, but I do not see another
"simple" possibility.For Dirichlet condition, you can indeed use add_explicit_matrix to add a constraint on certain nodes or add a constraint brick. For non Lagrange element, you can use
the previous strategy to build the constraint matrix, I think. Yves. Jean-Francois Barthelemy <address@hidden> a écrit :
Dear Getfem users, Is there any simple way in Getfem to impose lineic boundary conditions on a 3D problem ? To be more precise, I have a 3D mesh and I want to impose either Dirichlet or Neumann boundary conditions on a polyline. The first problem that arises is that, if I'm not wrong, the mesh_regions in 3D can be either volumes (convexes) or surfaces (convexe faces) but not 1D elements. However, as I can gather all the dof corresponding to the polyline, Dirichlet conditions can rather easily be handled by add_explicit_matrix and add_explicit_rhs methods. But the case of Neumann conditions may be a bit more difficult. Is there any straightforward method to do so ? Thank you very much Jean-Francois Barthelemy
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