On 8/18/24 21:02, Sean Carney wrote:
* For the case of adaptive refinement, the solution looks discontinuous also
at edges without refinement. Is that reasonable? What's the element you
are using?
I am currently using 2nd order FE_DGQ elements. Unfortunately, no, the
solution certainly should not be discontinuous
at any point in the domain.
But if the element is discontinuous, how do you enforce that the solution
"should not be discontinuous"?
My sense is that something is incorrect in my program's assemble_system
function, which in turn causes the computed
solution to be wrong. The picture from the adaptive refinement case was simply
intended to support this point.
To reiterate, what is incorrect is not an issue in the case of uniform
refinement--
if I take the mesh with 4x4 cells and refine to 8x8, the energy norm error
decreases accordingly. This continues with repeated
refinements; I see reasonable convergence rates as I drive $h$ to zero.
Short of posting my assemble_system code, does this behavior sound like
anything you have seen before?
Would be grateful for any other places to look.
There's a bug somewhere, as there always is :-) I'm sure many of us have seen
the sort of thing you're seeing, but what specifically the problem is is of
course hard to tell without actually knowing both the method and the code :-(
The only suggestion I have is to double-check that all lifting or
stabilization terms you have use a stabilization factor that is large enough
for the small edge size you have on the refined side, not just for the large edge.
Best
W.
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Wolfgang Bangerth email: [email protected]
www: http://www.math.colostate.edu/~bangerth/
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