On 1/17/20 9:11 PM, David Eaton wrote:
>
> Thanks the help from you and the others. The issue of discontinuous vorticity
> field is resolved. Theoretically, I understand the gradient should be
> discontinuous for C0 elements. However, I still want to convince myself with
> a explanation. while I used Q2Q1 Taylor-Hood element, the discontinuous
> contour still appear. What could be the reason for this?
And they should! You might be thinking that for Q2 functions, if you take the
gradient, you should still get a linear function that is continuous. But the
Q2 functions are only quadratic on each cell separately; they still have a
kink at cell interfaces, and consequently their gradient is discontinuous.
> On the other hand, I
> have a very simple FEM code using C0 elements without doing the projections.
> I just simply assembly the matrix, use a Lagrangian shape function in C0
> element and solve it with a linear solver. It does give a continuous contour
> without doing a projection. What could be the theoretical reason why it does
> not give a discontinuous contour? Is L2 projection is necessary step while
> computing gradients over elements for C0 elements?
Can you describe in mathematical terms what you do? When you say "assemble a
matrix" and "solve it", that sounds a lot like a projection to me.
Best
W.
--
------------------------------------------------------------------------
Wolfgang Bangerth email: bange...@colostate.edu
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 dealii+unsubscr...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/dealii/8c39a2a4-1b8c-7531-e52f-b13085978a38%40colostate.edu.
