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outputs from mphgetu and mphmatrix
Posted Oct 23, 2014, 2:17 p.m. EDT Interfacing, Studies & Solvers Version 4.3b 1 Reply
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I'm looking at a time-dependent 1D 'Coefficient Form PDE' problem. I mesh the line with 4 element (5 nodes). So I have 5 degrees of freedom, the relevant system matrices are also 5x5. Also to keep things simple, my shape function is linear.
However, when I use mphgetu(model), I get 7 values, among which only the 1,3,4,5,7th value correspond to u on the nodes. I guess the 2nd and the 6th value has something to do with the boundary? How exactly are they calculated?
Another question: How to get the Lagrange multiplier from mphmatrix?
Many thanks!
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Hello wdl
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I'm having the same problems. Did you figure out the relationship between solution vector index and variable value ? I recon that the two extra values you have are the internal degrees of freedom, though I am not quite sure I understand what they are.
Also regarding the system matrices, do you know what linear system does comsol solve ? I thought (keeping the matrix names given by mphmatrix) it would be:
E*Udotdot + D*Udot + K*U == L
But that doesn't appear to be the case...
Anyhow, I hope you eventually got an answer to your questions and thanks for sharing.
Regards,
Guillaume