How to define infinite extent elements in COMSOL?

In summary, the conversation discusses using infinite elements in a 1D model to simulate an infinite problem in the y-direction. The speaker suggests setting boundaries at the edge of the capacitor plates to account for the infinite extent. They also mention adjusting the computational area to end at the plates to eliminate any electric field below them. The questioner asks for clarification on how to adjust the settings in the provided image and if there is a specific boundary that needs to be defined for the 1D model in the x-direction.
  • #1
feynman1
435
29
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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  • #2
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.
 
  • #3
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.
 
  • #4
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?
 
  • #5
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.
 
  • #6
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?
 
  • #7
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
 

1. What is the definition of infinite extent elements in COMSOL?

Infinite extent elements in COMSOL refer to elements that have an infinite extent in one or more directions. These elements are used to model systems with infinite or large domains, such as waveguides, beams, and plates.

2. How do I define infinite extent elements in COMSOL?

To define infinite extent elements in COMSOL, you can use the Infinite Element Domain feature. This feature allows you to specify the infinite direction(s) and the size of the domain. You can also use the Infinite Element Boundary feature to define boundaries where the infinite element meets the finite element domain.

3. What are the benefits of using infinite extent elements in COMSOL?

Using infinite extent elements in COMSOL can provide more accurate results for systems with large or infinite domains. These elements can also reduce the computational time and memory usage compared to using a finite element mesh that covers the entire domain.

4. Can I use infinite extent elements in any type of COMSOL simulation?

No, infinite extent elements can only be used in certain types of simulations, such as electromagnetic, acoustic, and heat transfer simulations. They cannot be used in structural mechanics simulations, as these require a finite element mesh to accurately model the deformation of the structure.

5. Are there any limitations or considerations when using infinite extent elements in COMSOL?

Yes, there are some limitations and considerations when using infinite extent elements in COMSOL. These include the need to carefully choose the size of the domain and the number of elements used to ensure accurate results. Additionally, the use of infinite extent elements may not be necessary for all simulations and can increase the complexity of the model setup.

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