Dear Aaron Oaks,
In that example, the Dirichlet data is defined on mf_ue which is in fact not a
finite element space, it is defined to span a certain number of global
functions. So that the Dirichlet Data is a particular linear combination of
these global functions.
Of course, it is not possible to prescribe it exactly on the unknow which is
define on an enriched finite element space. So, here, the Dirichlet condition
is prescribed with a penalization technique. This means that a term
\int_{\Gamma} (u - Dirichlet_data) * gamma * Test_u
is added to the formulation, with gamma a penalization parameter (1e12 here).
Another possibility would be to prescribe the Dirichlet condition with a
Lagrange multiplier or with Nitsche's method.
Best regards,
Yves.
----- Original Message -----
From: "Oaks, Aaron Jameson" <[email protected]>
To: "getfem-users" <[email protected]>
Sent: Monday, July 13, 2015 9:01:20 PM
Subject: [Getfem-users] demo_crack.py Dirichlet condition
Greetings,
I am a PhD student at University of Illinois and I'm starting in on a project
studying crack propagation. I'm just starting out with GetFEM++ and FEM in
general, so I apologize if this question is remedial. I went through the
thermo-elastic and electrical coupling tutorial on the website, and that went
well, but going through the demo_crack.py example I'm having trouble seeing how
the Dirichlet BC is assigned. In the coupled tutorial I understood how it
worked using either a constant value or values interpolated on the same MeshFem
for each boundary node, but with all the different MeshFems in different bases
defined to accommodate the crack I seem to be at a loss. Could I get a
mathematical description of the Dirichlet condition to be assigned, and an
explanation of how the example code goes about assigning that condition? Thank
you very much for your time.
Aaron Oaks
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