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Impact of Zero Electrical Conductivity for Air on COMSOL Simulation Convergence

Posted Feb 7, 2024, 3:46 a.m. EST Materials Version 6.1 4 Replies

Haiyang Li
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The electrical conductivity of air in COMSOL is set to zero. Could this lead to non-convergence in the simulation results? I notice that others generally avoid setting a value of zero and instead use a very small value.

4 Replies Last Post Feb 8, 2024, 9:48 a.m. EST
Robert Koslover Certified Consultant
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Posted: 9 months ago Feb 7, 2024, 1:11 p.m. EST
Updated: 9 months ago Feb 7, 2024, 1:09 p.m. EST

In some cases, you should not set the conductivity to zero. In others, you may do so. You didn't mention which physics configuration you have chosen. Here is a related discussion: https://www.comsol.com/forum/thread/285781/Magnetic-field-created-by-a-DC-wire

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Scientific Applications & Research Associates (SARA) Inc.
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In some cases, you should not set the conductivity to zero. In others, you may do so. You didn't mention which physics configuration you have chosen. Here is a related discussion: https://www.comsol.com/forum/thread/285781/Magnetic-field-created-by-a-DC-wire
Haiyang Li
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Posted: 9 months ago Feb 7, 2024, 11:54 p.m. EST

In some cases, you should not set the conductivity to zero. In others, you may do so. You didn't mention which physics configuration you have chosen. Here is a related discussion: https://www.comsol.com/forum/thread/285781/Magnetic-field-created-by-a-DC-wire

Oh, thank you so much. I'm using Thermoelectric Effect modus. I think I made a mistake, just the non-triangular element is 0. Thank you for your explanition.

>In some cases, you should not set the conductivity to zero. In others, you may do so. You didn't mention which physics configuration you have chosen. Here is a related discussion: >https://www.comsol.com/forum/thread/285781/Magnetic-field-created-by-a-DC-wire Oh, thank you so much. I'm using Thermoelectric Effect modus. I think I made a mistake, just the non-triangular element is 0. Thank you for your explanition.
Alexander Petrov
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Posted: 9 months ago Feb 8, 2024, 9:10 a.m. EST

I'm not familiar with the Thermoelectric Effect module but I do know that the Magnetic Fields (mf) module (magnetic potential formulation) is just fine with resistivity of air being zero. At the same time, the Magnetic Field Formulation (mfh) module (H-formulation) is not. It depends on how the Maxwell equations are solved and whether they use conductivity or resistivity variables. If your simulation is running with conductivity of 0 and producing results then it's all good. If it isn't you will never converge at all.

I'm not familiar with the Thermoelectric Effect module but I do know that the Magnetic Fields (mf) module (magnetic potential formulation) is just fine with resistivity of air being zero. At the same time, the Magnetic Field Formulation (mfh) module (H-formulation) is not. It depends on how the Maxwell equations are solved and whether they use conductivity or resistivity variables. If your simulation is running with conductivity of 0 and producing results then it's all good. If it isn't you will never converge at all.
Jeff Hiller COMSOL Employee

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Posted: 9 months ago Feb 8, 2024, 9:48 a.m. EST
Updated: 9 months ago Feb 8, 2024, 9:51 a.m. EST

It would be interesting to get a more in-depth description of your model, or better yet, your mph file and a description of what you are trying to achieve with the model.

I am saying this because there is also a chance that you should not even be including the region occupied by air in your EM physics.

Jeff

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Jeff Hiller
It would be interesting to get a more in-depth description of your model, or better yet, your mph file and a description of what you are trying to achieve with the model. I am saying this because there is also a chance that you should not even be including the region occupied by air in your EM physics. Jeff

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