Nikki,
apologies for not getting to this any earlier!
I've recently implemented a 1d standard wave equation and have been messing
around with different boundary conditions. For instance, I have run my code
with 1 dirichlet and 1 neumann, 2 neumann, and 1 absorbing condition and 1
neumann (as in step-24). When I run step-23 from the examples, which utilizes
Dirichlet conditions, you can easily see the expected behavior of a phase flip
after interaction from the boundary, i.e. as the source approaches the
boundary it looks like a cap and after the boundary interaction it looks like
a cup. However, in all 3 cases that I have tried, listed above, I am not
observing the phase flip. No matter what boundary I change the left one to
(dirichlet, neumann, absorbing) it seems to be giving me the same neumann
behavior. Do you have any idea why this might be?
I don't see any specific thing that looks wrong, but then it's an 800 line
code -- not easy to see anything without spending a couple of hours with it.
But here's where I would start: Look at the difference between Dirichlet and
Neumann cases. If I see this right, setting up Dirichlet conditions happens in
line 319 for boundary zero, which in line 162 you seem to think of as the
right boundary. So does the call to VectorTools::interpolate_boundary_values
actually do anything? If you comment it out, does it change anything?
I suspect no: You put the result into the 'boundary_value_map' variable, but
that's a local variable whose lifetime ends at the end of the function, and it
is never used after calling VectorTools::interpolate_boundary_values. So that
looks like a bug -- or at least a pointless piece of code.
Of course, you do the same again in line 573. There, you seem to set the
elements of the solution vector to the correct boundary values, but you do not
touch the matrix. But you need to adjust the matrix before you solve with it
if you want to apply the correct set of boundary values -- take a look at
step-3, step-4, step-26, for example. In particular the last one.
Best
W.
--
------------------------------------------------------------------------
Wolfgang Bangerth email: [email protected]
www: http://www.math.colostate.edu/~bangerth/
--
The deal.II project is located at http://www.dealii.org/
For mailing list/forum options, see
https://groups.google.com/d/forum/dealii?hl=en
---
You received this message because you are subscribed to the Google Groups "deal.II User Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To view this discussion on the web visit
https://groups.google.com/d/msgid/dealii/63071152-2f7b-de45-8ede-71e91ad84e00%40colostate.edu.
