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Why the imported 3D variable through the “interpolation” does not imported correctly in COMSOL?

Posted Jun 19, 2018, 9:39 p.m. EDT Structural & Acoustics, Geomechanics Version 5.3 3 Replies

Wx Deng
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I have a solid mechanics problem to solve by COMSOL. The answer of first one (such as stress or displacement ) later replace as position dependent variable in second one.

There is two option. One way to do that is to export the answer from “Data Export” as a txt file and later import it in second COMSOL model by “interpolation”. Other way is to have two physics in one model and connect them by “Value of variable not solved for “in the sitting of “study”. When I import the data in second way and got the plot from the “interpolation” window everything is fine.

Unfortunately, there is problem with first way and the result at the end is not exactly same. Take von mises as a example. Maximum error can reach 14%. The error is mainly concentrated at the bottom.

With the nonlinear enhancement, the error is bigger and it locate in the all area. Maximum error can reach 60%.

I found that there is a difference between what I imported and what is read from those data.I don’t need interpolation. I will use same mesh. Therefore I just need to import a 3D variable correctly. The imported data is quite nonlinear. I look forward to hearing from you soon .

3 Replies Last Post Oct 22, 2018, 2:33 a.m. EDT
Jim Freels mechanical side of nuclear engineering, multiphysics analysis, COMSOL specialist
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Posted: 6 years ago Jun 28, 2018, 9:42 p.m. EDT

One question: Is this data imported only one time to establish initial conditions or constant data? If so, you can import by formatting the data correctly in the text file. See the manual on the correct way. If you intend to change this imported data at each iteration and generate the data using some external program, you will have convergence issues due to the decoupled nature of your problem. I would suggest to incorporate the physics altogether and allow COMSOL to solve all variables at once using solvers provided (direct, segregated, iterative, etc.).

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James D. Freels, Ph.D., P.E.
One question: Is this data imported only one time to establish initial conditions or constant data? If so, you can import by formatting the data correctly in the text file. See the manual on the correct way. If you intend to change this imported data at each iteration and generate the data using some external program, you will have convergence issues due to the decoupled nature of your problem. I would suggest to incorporate the physics altogether and allow COMSOL to solve all variables at once using solvers provided (direct, segregated, iterative, etc.).
Nichal Gentilal
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Posted: 6 years ago Jun 29, 2018, 2:25 p.m. EDT

Hi Deng,

I experienced the same problem. I tried to export with a extremely fine grid (very small discretizations) but I had some problems with that as well because COMSOL seems to have a limitation on the number of elements that it imports and exports (files >10 gb are usually problematic). Why don't you just use the 2nd option you suggested?

Regards, Nichal

Hi Deng, I experienced the same problem. I tried to export with a extremely fine grid (very small discretizations) but I had some problems with that as well because COMSOL seems to have a limitation on the number of elements that it imports and exports (files >10 gb are usually problematic). Why don't you just use the 2nd option you suggested? Regards, Nichal
Wx Deng
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Posted: 6 years ago Oct 22, 2018, 2:33 a.m. EDT
Updated: 6 years ago Oct 22, 2018, 2:34 a.m. EDT

Thank u for your reply. Sorry for the delay, I get the account recenlty. So you use the second option?

Thank u for your reply. Sorry for the delay, I get the account recenlty. So you use the second option?

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