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.