How to define infinite extent elements in COMSOL?

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Discussion Overview

The discussion centers around the definition and implementation of infinite extent elements in COMSOL, specifically in the context of modeling capacitor plates. Participants explore how to set boundaries and adjust settings for infinite elements in both x and y directions, addressing potential issues and configurations in a 1D model.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant questions the terminology change from 'infinite element' to 'infinite extent element', expressing unfamiliarity with the latter term.
  • Several participants suggest placing boundaries at the edges of the capacitor plates in the y direction, assuming constant potential for each plate.
  • In the x direction, a participant proposes treating the problem as 1D, indicating that the computational area should end with the plate to simulate infinite extent.
  • Another participant mentions that the dimensions not included in the model correspond to an infinite extent, suggesting that this aspect is already addressed.
  • A later reply raises a concern about obtaining different results when implementing a 1D model in the x direction, asking for clarification on specific boundary definitions needed for extension.

Areas of Agreement / Disagreement

Participants express varying opinions on the terminology and approach to defining infinite extent elements. While there is some agreement on boundary placements, the discussion remains unresolved regarding the specifics of implementing the 1D model and the implications of different results.

Contextual Notes

Participants have not fully clarified the assumptions underlying their proposed configurations, and there are unresolved questions regarding the boundary definitions necessary for the 1D model.

feynman1
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1592995338476.png

This figure shows 2 capacitor plates. Except the region in between the 2 plates, I want to set the others as infinite elements. How to 'stretch' the x and y directions in the infinite element settings?
 
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I don't know why my question was edited and changed from 'infinite element' to 'infinite extent element'. I've never heard of the latter.
 
In the y direction, I think you simply need to put the boundaries at the edge of the capacitor plates (considering you would put each plate at a constant potential).

For the x direction, you then have simply a 1D problem.
 
DrClaude said:
In the y direction, I think you simply need to put the boundaries at the edge of the capacitor plates (considering you would put each plate at a constant potential).

For the x direction, you then have simply a 1D problem.
Thanks. How to arrange the infinite element settings according to what you say?
 
feynman1 said:
Thanks. How to arrange the infinite element settings according to what you say?
The dimensions not included in the model corresponds to an infinite extent, so this is taken care of.

As for the other direction, I would simply make the computational area end with the plate. For example, in the 2D model you posted above, the line at R1 would be the same as the one at R6. COMSOL will then not compute any electric field below the bottom plate, which is equivalent to having the plate extend to infinity.
 
DrClaude said:
The dimensions not included in the model corresponds to an infinite extent, so this is taken care of.

As for the other direction, I would simply make the computational area end with the plate. For example, in the 2D model you posted above, the line at R1 would be the same as the one at R6. COMSOL will then not compute any electric field below the bottom plate, which is equivalent to having the plate extend to infinity.
1593165265948.png

How to adjust the setting in this pic?
 
DrClaude said:
In the y direction, I think you simply need to put the boundaries at the edge of the capacitor plates (considering you would put each plate at a constant potential).

For the x direction, you then have simply a 1D problem.

Hello Sir,
I implemented a 1D model in x-direction as the problem is infinite is infinite in y-direction. However, I obtained different results.
Is there a specific boundary I shall define to indicate that the 1D model in x-direction shall be extended?
Thanks in advance
 

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