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Solving Nonlinear Coupled PDEs

Posted May 7, 2015, 5:19 p.m. EDT Battery Design, Geometry, Studies & Solvers Version 4.4 4 Replies

Harikesh Arunachalam
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I am trying to simulate a micro-scale model. My unit cell consists of an anode spherical particle surrounded by electrolyte material. My problem is that while the system simulates, the results do not show any time variation for the solved variables. I am at a loss to understand how to enable the variables to update as a function of time. Kindly advise what is wrong in the attached model. (Dear Mr. Ivar Kjelberg, if you see this message, I would greatly appreciate your inputs).
4 Replies Last Post May 13, 2015, 10:06 a.m. EDT
DW
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Posted: 10 years ago May 8, 2015, 12:26 p.m. EDT
Hello,
If one tries to run your .MPH file one gets the error message below:
File not found.
- Filename: C:\Users\harunac\Desktop\Model Validation\E_neg_nondim.txt
- Function name: E_neg
Error in multiphysics compilation.
-DW
Hello, If one tries to run your .MPH file one gets the error message below: File not found. - Filename: C:\Users\harunac\Desktop\Model Validation\E_neg_nondim.txt - Function name: E_neg Error in multiphysics compilation. -DW
Harikesh Arunachalam
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Posted: 10 years ago May 8, 2015, 12:31 p.m. EDT
Hello,

I apologize. Please find attached the text file (I had to put it in a Zipped Folder) for the parameter E_neg_nondim.

I hope you can help resolve this issue that I am facing.

Thanks,

Harikesh
Hello, I apologize. Please find attached the text file (I had to put it in a Zipped Folder) for the parameter E_neg_nondim. I hope you can help resolve this issue that I am facing. Thanks, Harikesh

Attachments:

DW
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Posted: 10 years ago May 8, 2015, 10:49 p.m. EDT
Hello,
One point would be that the diffusion time should be on the order of L^2/D, so the value would be (24E-6m)^2/(5E-13m^2/s)=1152 seconds. Therefore, one should not see significant diffusion in 5 seconds. When one calculates the solution for c_1 it is still equal to the initial value of 0.065 after 5 seconds, and the calculated value of c_2 is still equal to the initial value of .393 after 5 seconds.
What is the source of your equations in the "problem statement"?
Don't you need a boundary condition for phi_1 at the "far" boundary (away from the active particle)?
-DW
Hello, One point would be that the diffusion time should be on the order of L^2/D, so the value would be (24E-6m)^2/(5E-13m^2/s)=1152 seconds. Therefore, one should not see significant diffusion in 5 seconds. When one calculates the solution for c_1 it is still equal to the initial value of 0.065 after 5 seconds, and the calculated value of c_2 is still equal to the initial value of .393 after 5 seconds. What is the source of your equations in the "problem statement"? Don't you need a boundary condition for phi_1 at the "far" boundary (away from the active particle)? -DW
Harikesh Arunachalam
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Posted: 10 years ago May 13, 2015, 10:06 a.m. EDT
Dear DW,

Please accept my sincere apologies for the delayed response. I was very sick over the last few days and could not get in touch with you earlier.

I completely agree with you regarding the time order of diffusion. I had completely overlooked this part. Thank you fro pointing that out. The only reason I simulated for 5 seconds is to see if the simulator would complete its process. It was taking a significant amount of time to solve the system.

I have attached the source of the equations for my problem statement. You will notice that I have non-dimensionalized the set of equations before inputting them in COMSOL.

In comparison with the attached document and my model, I am starting by solving the system for one anode particle surrounded by electrolyte, which constitutes 1 unit cell.

Perhaps I must also enforce a boundary condition for phi_1, since the solution (when I simulated for 5 seconds) I obtained for phi_1 and phi_2 did not have any physical meaning (extremely large values were observed). I neglected this earlier assuming it may not be required for a single unit cell, but only applies for an entire electrode system.

Please review, and let me know if there must be additional modifications to my model. In the meantime, I will enforce the phi_1 boundary condition and simulate the system for longer times.

Thank you very much.

Harikesh
Dear DW, Please accept my sincere apologies for the delayed response. I was very sick over the last few days and could not get in touch with you earlier. I completely agree with you regarding the time order of diffusion. I had completely overlooked this part. Thank you fro pointing that out. The only reason I simulated for 5 seconds is to see if the simulator would complete its process. It was taking a significant amount of time to solve the system. I have attached the source of the equations for my problem statement. You will notice that I have non-dimensionalized the set of equations before inputting them in COMSOL. In comparison with the attached document and my model, I am starting by solving the system for one anode particle surrounded by electrolyte, which constitutes 1 unit cell. Perhaps I must also enforce a boundary condition for phi_1, since the solution (when I simulated for 5 seconds) I obtained for phi_1 and phi_2 did not have any physical meaning (extremely large values were observed). I neglected this earlier assuming it may not be required for a single unit cell, but only applies for an entire electrode system. Please review, and let me know if there must be additional modifications to my model. In the meantime, I will enforce the phi_1 boundary condition and simulate the system for longer times. Thank you very much. Harikesh

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