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Warning sign in "Step 2: Time Dependent" node in COMSOL

Posted Jan 6, 2015, 2:14 p.m. EST Low-Frequency Electromagnetics, Studies & Solvers Version 4.4 4 Replies

Mohsen
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Hello guys,

I am solving a ODE in COMSOL which is coupled with AC/DC module through the velocity (Lorentz term) in "Magnetic and Electric fields" interface. When I choose "study controlled" in Equation form of this interface, as shown in picture 1.1 attached, the solver converges quickly and I get good results, at least their trends are reasonable. However, in this case, a "Waning sign" appears in the node "step 1: Time Dependent" which the picture 1.2 shows that. Is there any problem with this "Warning sign" or not?

Could you please tell me the here what does "study controlled" mean? I checked the COMSOL help but did not find related comments about this.

In another case, when I choose "Stationary" in Equation form of "Magnetic and Electric fields" interface, it can be seen in picture 2.1, the "Warning sign" disappear and I can see the "Green tick sign", see picture 2.2 please. But the problem is that my model in this case does not converges !!!

Any help or idea would be appreciated.

Thanks,
Mohsen
4 Replies Last Post Jul 5, 2017, 11:24 p.m. EDT
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Hello Mohsen

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Deepshikha Bhargava
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Posted: 7 years ago Jul 3, 2017, 10:52 p.m. EDT
Hi,
Did you find the solution for your problem?
I am having the same problem... please see the attached pics below.

Thanks
Hi, Did you find the solution for your problem? I am having the same problem... please see the attached pics below. Thanks
Magnus Ringh COMSOL Employee

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Posted: 7 years ago Jul 4, 2017, 4:05 a.m. EDT
Hi,

Choosing "Study controlled" (which is the default setting) means that the physics interface uses an equation form that is compatible with the study (a time-dependent equation form, for example). In this case, you are using a Time Dependent study together with a Magnetic and Electric Fields interface, which does not support any time-dependent form. That is why you see the warning icon in the table in the "Physics and Variables Selection" section. The warning icon indicates that that physics is not solved for even if it is selected in that table, in this case because the physics interface is not compatible with the study step.

Switching from a "Study controlled" equation form to a "Stationary" form, for example, removes this incompatibility (and the warning icon), but you may want to think about if you want to solve a stationary equation as part of a time-dependent simulation.

Best regards,
Magnus Ringh, COMSOL
Hi, Choosing "Study controlled" (which is the default setting) means that the physics interface uses an equation form that is compatible with the study (a time-dependent equation form, for example). In this case, you are using a Time Dependent study together with a Magnetic and Electric Fields interface, which does not support any time-dependent form. That is why you see the warning icon in the table in the "Physics and Variables Selection" section. The warning icon indicates that that physics is not solved for even if it is selected in that table, in this case because the physics interface is not compatible with the study step. Switching from a "Study controlled" equation form to a "Stationary" form, for example, removes this incompatibility (and the warning icon), but you may want to think about if you want to solve a stationary equation as part of a time-dependent simulation. Best regards, Magnus Ringh, COMSOL
Mohsen
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Posted: 7 years ago Jul 5, 2017, 11:23 p.m. EDT
Hi Deepshikha ,

Yes, I solved my problem. It backs to 2015!

I just used "Stationary" form. For the convergence problem, I think I assigned a small number to the electric conductivity of the surrounding air.

Good Luck,
Mohsen
Hi Deepshikha , Yes, I solved my problem. It backs to 2015! I just used "Stationary" form. For the convergence problem, I think I assigned a small number to the electric conductivity of the surrounding air. Good Luck, Mohsen
Mohsen
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Posted: 7 years ago Jul 5, 2017, 11:24 p.m. EDT
Thank you.
Thank you.

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