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Changing order of elements in Comsol4.2a

Posted 29 févr. 2012, 15:35 UTC−5 Version 4.2a 8 Replies

Abid Saeed
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Hi everyone,

I am new to comsol, I just want to solve some classical PDEs on curved domains using different orders of elements particularly higher order isoparametric elements.

I solved eigenvalue problem for Laplacian over a circle for default order of elements which is quadratic.

But when I want to solve the same problem over same mesh with different higher order by changing order in Element order list it does not solve the problem for new order. it solves problem with same default quadratic element (i.e. it repeats the old problem and delivers same answer) as one can see from degree of freedom.

Can anyone please help me what I am missing here.

Thank you in advance.
8 Replies Last Post 5 mars 2012, 19:24 UTC−5
Alexander Kuznetsov
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Posted: 1 decade ago 29 févr. 2012, 17:59 UTC−5
I just checked it and it works fine for me. I used PDE (c) and change order in PDE Settings - Discretization - Element Order. DoF increased from 1217 for quadratic to 4745 for quartic
I just checked it and it works fine for me. I used PDE (c) and change order in PDE Settings - Discretization - Element Order. DoF increased from 1217 for quadratic to 4745 for quartic
Abid Saeed
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Posted: 1 decade ago 1 mars 2012, 13:21 UTC−5

Thankyou for your help.

I think you talking about comsol 3.5a. I tried in comsol 3.5a and it worked there as you said. But if I use latest version i.e. comsol 4.2 and change element order in Discretization - Element Order, it does not work. I dont know why?

Would be good if I am able to solve it using latest version of comsol as well.

Anyway thanks again.

Abid
Thankyou for your help. I think you talking about comsol 3.5a. I tried in comsol 3.5a and it worked there as you said. But if I use latest version i.e. comsol 4.2 and change element order in Discretization - Element Order, it does not work. I dont know why? Would be good if I am able to solve it using latest version of comsol as well. Anyway thanks again. Abid
Abid Saeed
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Posted: 1 decade ago 2 mars 2012, 15:11 UTC−5

Hellow again,

I solved eigenvalues problem using comsol3.5a. Now I want to export all eigenvalues but i could not do it. I exported the mesh by going through File-Export-Mesh to file.....but i dont see how to export all calculated eigenvalues.

Any one help me please.

Thanks in advance.
Hellow again, I solved eigenvalues problem using comsol3.5a. Now I want to export all eigenvalues but i could not do it. I exported the mesh by going through File-Export-Mesh to file.....but i dont see how to export all calculated eigenvalues. Any one help me please. Thanks in advance.
Alexander Kuznetsov
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Posted: 1 decade ago 2 mars 2012, 15:33 UTC−5
No, I was talking about 4.2a. It works for me. Probably you do something differently. Upload your model so I can have a look.
No, I was talking about 4.2a. It works for me. Probably you do something differently. Upload your model so I can have a look.
Abid Saeed
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Posted: 1 decade ago 2 mars 2012, 15:58 UTC−5

Hi Alexander,

Please have a look at files I am sending you both m.file and .mph files.

And also tell me about exporting calculated eigenvalues.

Thanks.
Hi Alexander, Please have a look at files I am sending you both m.file and .mph files. And also tell me about exporting calculated eigenvalues. Thanks.
Alexander Kuznetsov
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Posted: 1 decade ago 2 mars 2012, 16:57 UTC−5
Here are my results after changing discretization order:

Quadratic:
Number of degrees of freedom solved for: 93.
Solution time (Study 1): 1 s.

Quintic:
Number of degrees of freedom solved for: 531.
Solution time (Study 1): 1 s.

But I changed it in the different place. Next to the "Model Builder" on top there is "Show" button. Click it to bring the menu. There you select "Discretization". Then click on PDE (c) node and in "settings" you will see that new section called "Discretization" appeared. There you can change your element order.

And sorry, I can't help you with eigenvalues.
Here are my results after changing discretization order: Quadratic: Number of degrees of freedom solved for: 93. Solution time (Study 1): 1 s. Quintic: Number of degrees of freedom solved for: 531. Solution time (Study 1): 1 s. But I changed it in the different place. Next to the "Model Builder" on top there is "Show" button. Click it to bring the menu. There you select "Discretization". Then click on PDE (c) node and in "settings" you will see that new section called "Discretization" appeared. There you can change your element order. And sorry, I can't help you with eigenvalues.
Abid Saeed
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Posted: 1 decade ago 5 mars 2012, 14:43 UTC−5


Thankyou so much Alexander it worked now.

One more thing I wanted to make sure that comsol uses the isoparametric elements of same order for domain with curved boundaries. Do you know that comsol is realy doing this what i want?


Abid
Thankyou so much Alexander it worked now. One more thing I wanted to make sure that comsol uses the isoparametric elements of same order for domain with curved boundaries. Do you know that comsol is realy doing this what i want? Abid
Alexander Kuznetsov
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Posted: 1 decade ago 5 mars 2012, 19:24 UTC−5
I'm not sure what you are asking about. If it's about curvilinear elements, then I don't think COMSOL uses them.
I'm not sure what you are asking about. If it's about curvilinear elements, then I don't think COMSOL uses them.

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