On Wednesday 04 June 2008 10:30, Sébastien Janas wrote:
Hi all,
I want to solve the transient linear equation of diffusion.
It seems that there is no function pre-build in getfem for the
transient problems. So I assemble the mass matrix (MM) and stiffness
matrix (SM) "manually", and then construct the linear system A*X=B
using the backward euler
A = (MM + delta t * SM)
B = MM * X(t-1)
Then I have to impose dirichlet conditions on the surface. I import
my
mesh from gmsh, where the surface are tagged with a number (in my
case
200). How can I modify my linear system to take into accompt the
dirichlet conditions? All the functions I found in the documentation
are in the case where you use model bricks or standard assembly
procedures...
If I can have the list of node numbers tagged by 200 I would use the
penalty method. But I am not able to obtain these list.
I am using the python interface of getfem.
Thanks for your help,
Best regards,
Janas Sébastien
This is true that there is no general strategy proposed for transient
problems, especially with the matlab or python interfaces. This is
however
not easy to build such a general strategy since the situation can
vary a lot
for differente time integration schemes.
However, You can have the list of nodes on a boundary with the command
gf_mesh_fem_get(MF, 'dof on region', [bnum]);
but you have first to tag the boundary with the command
gf_mesh_set(M, 'region', int bnum, imat CVFLST);
(see the Matlab examples).
Yves.