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Maximum number of Newton iterations reached.

Posted 31 août 2018, 06:54 UTC−4 Studies & Solvers Version 5.3a 6 Replies

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Hello everybody I'm currently trying to design a heat transfer with electric flow in Comsol. and I could not solve this problem for a few days. The problem is that every time I get an error saying: Feature: Stationary Solver 1 (sol1 / s1) Failed to find a solution. Maximum number of newton iterations reached. There is an error message from the linear solver. The relative error (14) is greater than the relative tolerance. Returned solution is not converged. Not all parameter steps returned.

I also found some possible solutions on the internet, but they do not work for me. The possibilities were eg: change the "Maximum number of iterations" to 1000 under the Fully Coupled . or change Relative tolerance to a number less than 1. eg 0.1.

Thanks for the help.

6 Replies Last Post 12 sept. 2018, 17:27 UTC−4
Jeff Hiller COMSOL Employee

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Posted: 6 years ago 31 août 2018, 08:47 UTC−4

Given what you've already tried, one possibility is that your model is set up in such a way as not to have one and only one solution. For instance, if you have a volumetric heat source and all the boundaries are insulated, there is no stationary solution to the model. Or if you have no volumetric heat source and all the boundaries are insulated, there is an infinite number of solutions (in the absence of temperature constraint anywhere).

Could be a number of other things. You may want to post your mph file for more specific answers.

Jeff

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Jeff Hiller
Given what you've already tried, one possibility is that your model is set up in such a way as not to have one and only one solution. For instance, if you have a volumetric heat source and all the boundaries are insulated, there is no stationary solution to the model. Or if you have no volumetric heat source and all the boundaries are insulated, there is an infinite number of solutions (in the absence of temperature constraint anywhere). Could be a number of other things. You may want to post your mph file for more specific answers. Jeff
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Posted: 6 years ago 7 sept. 2018, 03:20 UTC−4

Hello Jeff, Thank you for your answer. I think the problem is with Mesh. But I do not know, what should I change. Here I upload my file. I hope you can help me.

Thanks

Hello Jeff, Thank you for your answer. I think the problem is with Mesh. But I do not know, what should I change. Here I upload my file. I hope you can help me. Thanks

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Jeff Hiller COMSOL Employee

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Posted: 6 years ago 7 sept. 2018, 09:09 UTC−4

It looks like the problem is an electric version of my first guess ("For instance, if you have a volumetric heat source and all the boundaries are insulated, there is no stationary solution to the model."). Here you have an electrical source term in the form of your terminal, but there's nowhere for the current to exit because all boundaries are insulated.

You can make the problem physical by, for instance, setting an electric potential (or a ground) boundary condition somewhere.

Jeff

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Jeff Hiller
It looks like the problem is an electric version of my first guess ("For instance, if you have a volumetric heat source and all the boundaries are insulated, there is no stationary solution to the model."). Here you have an electrical source term in the form of your terminal, but there's nowhere for the current to exit because all boundaries are insulated. You can make the problem physical by, for instance, setting an electric potential (or a ground) boundary condition somewhere. Jeff
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Posted: 6 years ago 10 sept. 2018, 06:34 UTC−4
Updated: 6 years ago 10 sept. 2018, 06:50 UTC−4

It looks like the problem is an electric version of my first guess ("For instance, if you have a volumetric heat source and all the boundaries are insulated, there is no stationary solution to the model."). Here you have an electrical source term in the form of your terminal, but there's nowhere for the current to exit because all boundaries are insulated.

You can make the problem physical by, for instance, setting an electric potential (or a ground) boundary condition somewhere.

Jeff

Thanks for the answer. I have now selected the bottom side as ground. There are still errors in Algebraic Multigrid Solver (ht) and Geometric Multigrid Solver (ht). Can you please help me with this? I also want to define the temperatures [K] as variables in parameters. That means: I do not know with 4A electric current how hot will be the components . what can I write as an expression?

  • Actually, this simulation is for me to be able to read the final temperature at the end

Thanks

>It looks like the problem is an electric version of my first guess ("For instance, if you have a volumetric heat source and all the boundaries are insulated, there is no stationary solution to the model."). Here you have an electrical source term in the form of your terminal, but there's nowhere for the current to exit because all boundaries are insulated. > >You can make the problem physical by, for instance, setting an electric potential (or a ground) boundary condition somewhere. > >Jeff Thanks for the answer. I have now selected the bottom side as ground. There are still errors in Algebraic Multigrid Solver (ht) and Geometric Multigrid Solver (ht). Can you please help me with this? I also want to define the temperatures [K] as variables in parameters. That means: I do not know with 4A electric current how hot will be the components . what can I write as an expression? * Actually, this simulation is for me to be able to read the final temperature at the end Thanks

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Jeff Hiller COMSOL Employee

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Posted: 6 years ago 10 sept. 2018, 09:15 UTC−4

I am afraid I don't understand why you made the changes you made to the model and introduced T1 and T2, which are undefined as far as I can see, causing the new error.

I would encourage you to contact COMSOL's support team for a more in depth discussion of your goals.

Best,

Jeff

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Jeff Hiller
I am afraid I don't understand why you made the changes you made to the model and introduced T1 and T2, which are undefined as far as I can see, causing the new error. I would encourage you to contact COMSOL's support team for a more in depth discussion of your goals. Best, Jeff
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Posted: 6 years ago 12 sept. 2018, 17:27 UTC−4

Hi Jeff, Thank you again for your answer. I have in the copper (the small piece) 4 A electric current. The initial temperature is -5 degC. I want to know what will be the temperatures of these two components (copper and kapton) at the end. I wrote T1 and T2 because I do not know the final temperature. And also do not know how should I define them as parameters. Do you mean that I should not change the default temperature (293.15 K) ?

Best regards

Hi Jeff, Thank you again for your answer. I have in the copper (the small piece) 4 A electric current. The initial temperature is -5 degC. I want to know what will be the temperatures of these two components (copper and kapton) at the end. I wrote T1 and T2 because I do not know the final temperature. And also do not know how should I define them as parameters. Do you mean that I should not change the default temperature (293.15 K) ? Best regards

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