How to implement inhomogeneous Dirichlet boundary conditions? about gimli HOT 4 CLOSED

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I can confirm the issue.

A quick test with the new fea implementation (yet unpublished) shows the resulting field need to be exact and mesh independend due to the bilinear field characteristics:

Its a little unclear where this comes from and when I will have time to fix it. In the meantime you can set the Dirichlet values to the nodes directly which seems to work as expected.

def BCN(node):
    return (-X * node.x() -Y * node.y())
bc={'Node': [[b.node(0).id(), BCN(b.node(0))] for b in mesh.findBoundaryByMarker(1,5)]}
uh = pg.solve(mesh, a=[[1, 1]], bc=bc, verbose=True)
u = (-pg.x(mesh) - pg.y(mesh))
print('normL2(u-uh):', pg.solver.normL2(u-uh, mesh))

Also there seems an issue with the showMesh keyword argument in the current release which I need to fix.

Many thanks for reporting,
Carsten

Edit: Added the code for normL2 calculation
Edit 2: The workarround only works for p=1 meshes, for p=2 also the middle node (b.node(2)) need to be considered.

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The problem comes from the numbering directions of the boundary nodes. Not every node(0) is connected to node(1) from its neighbour, some are screwed due to triangle. So if you assign the value for one boundary to its node(0) might lead to wrong assigments. This is unfortunately broken be 'very old design' and I'm unsure if this can be fixed with moderate afford. Until the new implementation comes online, the little bit unconveniant direct node assignment will work.

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Hi @carsten-forty2,

thanks for the quick and insightful response!

The news about a re-implementation of the FE code basis is great!

Cheers,
Ralph

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