Re: [deal.II] In example 40, the results are significantly different between the first-order and second-order finite element meshes

2023-11-15 Thread Abbas Ballout 

ztdep, 
You got me curious 

You can output the results of the Kelly error estimate with something like 
this in the data output: 








*Vector 
estimated_error_per_cell(triangulation.n_active_cells());
KellyErrorEstimator::estimate(dof_handler,QGauss(fe.degree + 1),std::map 
*>(),locally_relevant_solution,estimated_error_per_cell);  
  data_out.add_data_vector(estimated_error_per_cell, "kelly");*

and you'll see that the estimate is horrible with fe(1). Why? because the 
estimate is based on the jump of the gradients across cells and fe(1) isn't 
cutting it 
So if you output the gradient with:


*GradientPostprocessor gradient_postprocessor;
data_out.add_data_vector(locally_relevant_solution, 
gradient_postprocessor);*
(copy paste the postprocessor 
from 
https://www.dealii.org/current/doxygen/deal.II/classDataPostprocessorVector.html)
 

You can see in Paraview that the gradient doesn't look continuous/clean 
across elements when you use fe(1). 
So this isn't weird and unexpected. 

Apparently the gradient approx with bi-linear fe(1) is bad? 
The only way would be for me to be 100% sure would be to write these terms 
down and check for myself. 
If you do it let me know. 


On Monday, November 13, 2023 at 1:45:17 PM UTC+1 blais...@gmail.com wrote:

> Changing to Fe1 really alters the solution, so consequently the kelly 
> error estimator will also give you a different error estimation and thus a 
> different mesh adaptation.
> If your mesh adaptation is based on an error estimator, altering the 
> finite element interpolation order will alter the solution and thus alter 
> the mesh adaptation process.
>
>
> On Monday, November 6, 2023 at 9:13:31 p.m. UTC-5 ztdep...@gmail.com 
> wrote:
>
>>
>> The default setting is  'fe(2)" , we can clearly see a refined region in 
>>  the resulting mesh. While after i changed it to "fe(1)", we cann't see 
>> this region.  
>> This is what i wnat to know .
>> ztdepyahoo
>> ztdep...@gmail.com
>>
>> 
>>  
>>  Replied Message  
>> From Wolfgang Bangerth 
>> Date 11/7/2023 02:59 
>> To  
>> Subject Re: [deal.II] In example 40, the results are significantly 
>> different between the first-order and second-order finite element meshes 
>> On 11/6/23 03:12, ztdep...@gmail.com wrote:
>>
>> **
>>
>> the adaptivited mesh are very diffent as shown in attachments.
>>
>>
>> @ztdep:
>> We don't actually know what you are asking: Your post has no question. We 
>> also 
>> don't know what it is you did: The post doesn't show how you modified 
>> step-40. 
>> Finally, you do not say why you think that the result is wrong or 
>> surprising: 
>> You just show a picture, but for all we know this may be correct.
>>
>> Please spend a bit of thought in formulating questions in such a way that 
>> it 
>> is clear what you are asking, why you are asking it, and what is behind 
>> the 
>> question you are asking.
>>
>> Best
>> W.
>>
>> -- 
>> 
>> Wolfgang Bangerth  email: bang...@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
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>> .
>>
>

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Re: [deal.II] In example 40, the results are significantly different between the first-order and second-order finite element meshes

2023-11-13 Thread blais...@gmail.com 
Changing to Fe1 really alters the solution, so consequently the kelly error 
estimator will also give you a different error estimation and thus a 
different mesh adaptation.
If your mesh adaptation is based on an error estimator, altering the finite 
element interpolation order will alter the solution and thus alter the mesh 
adaptation process.


On Monday, November 6, 2023 at 9:13:31 p.m. UTC-5 ztdep...@gmail.com wrote:

>
> The default setting is  'fe(2)" , we can clearly see a refined region in 
>  the resulting mesh. While after i changed it to "fe(1)", we cann't see 
> this region.  
> This is what i wnat to know .
> ztdepyahoo
> ztdep...@gmail.com
>
> 
>  
>  Replied Message  
> From Wolfgang Bangerth 
> Date 11/7/2023 02:59 
> To  
> Subject Re: [deal.II] In example 40, the results are significantly 
> different between the first-order and second-order finite element meshes 
> On 11/6/23 03:12, ztdep...@gmail.com wrote:
>
> **
>
> the adaptivited mesh are very diffent as shown in attachments.
>
>
> @ztdep:
> We don't actually know what you are asking: Your post has no question. We 
> also 
> don't know what it is you did: The post doesn't show how you modified 
> step-40. 
> Finally, you do not say why you think that the result is wrong or 
> surprising: 
> You just show a picture, but for all we know this may be correct.
>
> Please spend a bit of thought in formulating questions in such a way that 
> it 
> is clear what you are asking, why you are asking it, and what is behind 
> the 
> question you are asking.
>
> Best
> W.
>
> -- 
> 
> Wolfgang Bangerth  email: bang...@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 a topic in the 
> Google Groups "deal.II User Group" group.
> To unsubscribe from this topic, visit 
> https://groups.google.com/d/topic/dealii/VcsXMXhl_YQ/unsubscribe.
> To unsubscribe from this group and all its topics, send an email to 
> dealii+un...@googlegroups.com.
> To view this discussion on the web visit 
> https://groups.google.com/d/msgid/dealii/e17928b7-f1d0-e5f2-83b9-872ba95e492a%40colostate.edu
> .
>

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Re: [deal.II] In example 40, the results are significantly different between the first-order and second-order finite element meshes

2023-11-06 Thread ztdepyahoo 







The default setting is  'fe(2)" , we can clearly see a refined region in  the resulting mesh. While after i changed it to "fe(1)", we cann't see this region. 
This is what i wnat to know .
 


ztdepyahooztdepya...@gmail.com


 

  
 Replied Message 
  
  

  

 From 


Wolfgang Bangerth


  
  

 Date 


11/7/2023 02:59

  
  

 To 


 
  


  

  
  

 Subject 


  Re: [deal.II] In example 40, the results are significantly different between the first-order and second-order finite element meshes

  

  
On 11/6/23 03:12, ztdep...@gmail.com wrote: **  the adaptivited mesh are very diffent as shown in attachments.@ztdep:We don't actually know what you are asking: Your post has no question. We also don't know what it is you did: The post doesn't show how you modified step-40. Finally, you do not say why you think that the result is wrong or surprising: You just show a picture, but for all we know this may be correct.Please spend a bit of thought in formulating questions in such a way that it is clear what you are asking, why you are asking it, and what is behind the question you are asking.Best  W.-- Wolfgang Bangerth  email: bange...@colostate.eduwww: 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 a topic in the Google Groups "deal.II User Group" group.To unsubscribe from this topic, visit https://groups.google.com/d/topic/dealii/VcsXMXhl_YQ/unsubscribe.To unsubscribe from this group and all its topics, send an email to dealii+unsubscr...@googlegroups.com.To view this discussion on the web visit https://groups.google.com/d/msgid/dealii/e17928b7-f1d0-e5f2-83b9-872ba95e492a%40colostate.edu.




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Re: [deal.II] In example 40, the results are significantly different between the first-order and second-order finite element meshes

2023-11-06 Thread Wolfgang Bangerth 

On 11/6/23 03:12, ztdep...@gmail.com wrote:

**

the adaptivited mesh are very diffent as shown in attachments.


@ztdep:
We don't actually know what you are asking: Your post has no question. We also 
don't know what it is you did: The post doesn't show how you modified step-40. 
Finally, you do not say why you think that the result is wrong or surprising: 
You just show a picture, but for all we know this may be correct.


Please spend a bit of thought in formulating questions in such a way that it 
is clear what you are asking, why you are asking it, and what is behind the 
question you are asking.


Best
 W.

--

Wolfgang Bangerth  email: bange...@colostate.edu
   www: http://www.math.colostate.edu/~bangerth/


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