Markus,
Thank you for your response.
Hello Justin,
does the error go down for degree 0, if you use a finer grid?
Yes, it decreases exactly as expected as the grid becomes finer. The
problem is very well-behaved in that regard.
Why do you have to reimplement the curl?
Best Regards,
Markus
I didn't know there was one already implemented! (It's not in the
FEValues class, right?) Does it compute the curl differently?
Best,
-J
Hello Justin,
does the error go down for degree 0, if you use a finer grid? Why do
you have to reimplement the curl?
Best Regards,
Markus
On 05.04.2012 04:56, Justin Droba wrote:
Hi,
First, I want to thank the authors of this software package and the
tutorials for all their hard work. The latter are especially
excellent and really make learning this extensive package very easy
and intuitive. I'm having a bit of trouble with high-order Nedelec
Elements. Everything compiles and runs without error, but when I use
an order higher than 0, the computed solution is very poor. Using one
of the 2D examples from Anna's paper, with order 0 elements, on a
certain small grid I get an L2 error of 1.610e-01, but when I use
order 1, I get an error of 8.722. From what I understand, the
gradients of Nedelec elements are not computed correctly, but when
one uses them to compute the curl, the "wrong parts cancel" and the
curl ends up correct. Is that right? I am using a self-written curl
function, implemented in the obvious way (for 2D only, here):
template<int dim>
double MaxwellToy<dim>::curl (const Tensor<2,2> &Gradients) const
{
return (Gradients[1][0] - Gradients[0][1]);
}
Do I need to do something special to make Nedelec elements work for
orders > 0? Is it a matter of something like enforcing a divergence
condition on the elements? The field I am attempting to compute is
div free, and for order 0 elements, we have that automatically (but
not for order 1 elements). Thanks for your help!
Best,
-J
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