Professor Wolfgang Bangerth and Bruno Blais,
Thank you for your explanations. I get clear about this problem now.
Best
D.
________________________________
From: dealii@googlegroups.com <dealii@googlegroups.com> on behalf of Wolfgang
Bangerth <bange...@colostate.edu>
Sent: Tuesday, January 21, 2020 11:48 PM
To: dealii@googlegroups.com <dealii@googlegroups.com>
Subject: Re: [deal.II] discontinous contour over elements
On 1/18/20 5:02 PM, David Eaton wrote:
> I just use tecplot directly visualize the results. The vorticity contour from
> my simple code is continuous, and the results from deal.II is discontinuous
> (without L2 projection).
Ah, I think that is it. Bruno was already on the right track.
I bet that your own code outputs the solution in a way that assigns only one
value to each node, and tecplot then computes a discontinuous gradient that it
averages at each node again from the adjacent cells. On the other hand,
deal.II outputs the value at each node as many times as there are adjacent
cells, and tecplot doesn't know how to average in that case.
In other words, what tecplot is doing *internally* is to do a projection (or
some other averaging operation) so that it *shows* you a continuous gradient
or vorticity field. But this is just another case where what you *see* is not
actually what it *is*. The gradient is discontinuous, regardless of what
tecplot shows you.
Best
W.
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Wolfgang Bangerth email: bange...@colostate.edu
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