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Solving nonlinear problem using parameter sweep

Posted Mar 6, 2012, 9:38 p.m. EST RF & Microwave Engineering, Studies & Solvers Version 4.0a, Version 4.1, Version 4.2, Version 4.2a 4 Replies

Zhiqi Zhang
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Hi, everyone!

I am struggling to solve some nonlinear optical problem (the material has 3rd-order nonlinear optical response to the electrical-magnetic field) using Comsol RF-frequency domain module. But when the nonlinear become significant enough, the calculation can not converge.
I heard that the problem may be solved by using parameter sweep and adding the nonlinear parameter gradually, but I am not sure the right way to do that, I have set

Study 1 > Solver Configurations > Dependent Variables: Initial Values of Variables Solved For / Not Solved For > Method: Initial Expression, Solution: Solver 1

Is that enough? Under the "Mehtod" tab there is another choice as " Solution" , what's the difference with "Initial Expression"? which one should I choose? Under the "Solution" tab there is also another choice as "Parametric 1", what's the difference then?

Is there any thing else I should do? Does anyone has suggestions about how to correctly solve such nonlinear problem?

Thank you!

Best regards!
Zhiqi
4 Replies Last Post Jan 4, 2016, 12:06 p.m. EST
Alexander Kuznetsov
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Posted: 1 decade ago Mar 6, 2012, 9:56 p.m. EST
If you are using iterative solver, try changing it to direct. For RF-simulations, it helps with convergence in many cases.
If you are using iterative solver, try changing it to direct. For RF-simulations, it helps with convergence in many cases.
Zhiqi Zhang
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Posted: 1 decade ago Mar 7, 2012, 4:45 a.m. EST
Thank you, I used the default solver.

under Stationary solver --> "Direct" tab, it is "MUMPS" solver,
under Stationary solver --> "Fully coupled" tab, the linear slover is "Direct".

I don't know which one do you mean?
Thank you, I used the default solver. under Stationary solver --> "Direct" tab, it is "MUMPS" solver, under Stationary solver --> "Fully coupled" tab, the linear slover is "Direct". I don't know which one do you mean?
Maurice Sesay
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Posted: 1 decade ago Jun 13, 2012, 10:05 p.m. EDT
Hi,
How did you use COMSOL to solve the nonlinear response? can you please send me the module file.
Regards,
Maurice
Hi, How did you use COMSOL to solve the nonlinear response? can you please send me the module file. Regards, Maurice
Sriram Guddala
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Posted: 9 years ago Jan 4, 2016, 12:06 p.m. EST
HI Zhang,
I am also having the similar confusions that you have faced during nonlinear problem solving. If you have any progress, plese could you share your file. Especially for parametric sweep I am not able to figure out the way to call the intial parameter.

Thanks in advance for the files.

sriram
HI Zhang, I am also having the similar confusions that you have faced during nonlinear problem solving. If you have any progress, plese could you share your file. Especially for parametric sweep I am not able to figure out the way to call the intial parameter. Thanks in advance for the files. sriram

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