What method does COMSOL use to interpolate post processing data?

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Discussion Overview

The discussion revolves around the method used by COMSOL to interpolate post-processing data, specifically regarding the interpolation of potentials in a volume conductor. Participants explore different interpolation methods based on the finite element model's order and provide insights into the implications of using various element orders.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about the specific interpolation method and its order used by COMSOL for exporting potentials at arbitrary locations.
  • Another suggests checking the post-processing and subdomain integration features in COMSOL, although they express uncertainty about the effectiveness of this approach.
  • A participant notes that the interpolation method depends on the order of the finite element model, indicating that first-order elements will result in linear interpolation, while elements with mid-side nodes allow for quadratic interpolation.
  • One participant advocates for using the highest order elements possible, suggesting quartic elements, but also humorously reflects on the computational strain this may cause.
  • A later reply counters the suggestion of using quartic elements, arguing that there is a trade-off between element order and the number of elements, and expresses skepticism about the necessity of quartic elements for most problems.
  • Another participant acknowledges the sarcasm in the previous message regarding the computational demands of high-order elements.

Areas of Agreement / Disagreement

Participants express differing views on the necessity and efficiency of using higher-order elements for interpolation, indicating that multiple competing perspectives remain on the best approach to take.

Contextual Notes

There are unresolved assumptions regarding the specific conditions under which different interpolation methods may be preferred, as well as the computational limitations associated with higher-order elements.

mjb7
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I'm computing the potentials in a volume conductor. I can get the potentials at any arbitrary location using the File->Export->Post Processing Data. Anybody know what method (and its order) COMSOL uses to interpolate the potentials at the arbitrary locations?
 
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try post processing, subdomain integration, and click the help button. it will probably answer your questions, but I am not sure. I've never used the export tool except for meshes
 
It will depend on what order element is being used for the finite element model. First-order (no mid-side nodes) will be a linear interpolation, while single mid-side nodes will allow for a quadratic interpolation across each element.
 
i suggest using the highest order you can... quartic i think? Tax ur computer like crazy and see comsols full potential. I ran my quad core at 100% all night once and got nowhere. I was sad because i probably cut like a year off my computers life haha.
 
Nick Bruno said:
i suggest using the highest order you can... quartic i think? Tax ur computer like crazy and see comsols full potential. I ran my quad core at 100% all night once and got nowhere. I was sad because i probably cut like a year off my computers life haha.

That is of course a waste. There is a trade-off between the order element being used and the number of elements in the model; usually, it's better to use more lower-order elements than fewer higher-order elements, but it will vary from case to case. I seriously doubt quartic elements are necessary in any problem. Ever.
 
lol sorry if u didnt pic up on my sarcasm
 

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