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Help with "Nonlinear solver did not converge"
Posted 24 mars 2014, 07:55 UTC−4 Fluid & Heat, Chemical Reaction Engineering, Studies & Solvers Version 4.4 1 Reply
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Good day everyone!
I am working on a multiphysics problem involving reaction engineering, thermal stress, fluid flow in porous media, and species transport in porous media. At a certain timestep, I receive the error:
"
Nonlinear solver did not converge.
Maximum number of iterations reached.
Time: [max time solved for]
Last time step is not converged.
"
I am using a fully coupled (advanced, direct) solver for now, as I haven't been able to get a segregated solver to converge for even the first time step. My question is this: Is there any way I can go into the log files and find out which of my dependent variables is causing the convergence problem?
Thank you all!
-Nathan
I am working on a multiphysics problem involving reaction engineering, thermal stress, fluid flow in porous media, and species transport in porous media. At a certain timestep, I receive the error:
"
Nonlinear solver did not converge.
Maximum number of iterations reached.
Time: [max time solved for]
Last time step is not converged.
"
I am using a fully coupled (advanced, direct) solver for now, as I haven't been able to get a segregated solver to converge for even the first time step. My question is this: Is there any way I can go into the log files and find out which of my dependent variables is causing the convergence problem?
Thank you all!
-Nathan
1 Reply Last Post 26 mars 2014, 08:16 UTC−4
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Posted:
1 decade ago
I have found the solution to my problem.
Although I could not explicitly identify the nonconvergent dependent variable, I was able to figure out iteratively which one was the offender. I suspect that the reason this was difficult is that most of my dependent variables are couples. This means, for instance, that if the offending dependent variable was concentration of a species, it may behave aberrantly near my final converged timestep, but so would the fluid velocity field, or pressure, or stress.
I ultimately guessed that the nonconverging dependent variable was the velocity field. In order to test that hypothesis, I went under the following interface:
Study 1 >> Solver Configurations >> Dependent Variables (I only have one solver step) >> Velocity Field
In this interface, I expanded the "Scaling" menu, and selected "Initial Value Based" from the drop down menu. My solution then converged, even for timesteps past where it had been failing before!
If velocity field had not been the nonconvergent dependent variable, I would have reset the scaling to the default (in my case, it was "From Parent"), and tried the same process on the next most likely candidate (in my case, concentration of gas).
I still don't know if there is a way to explicitly identify a nonconvergent dependent variable in a fully-coupled multiphysics problem. However, if someone knows how to do this, feel free to post here!
-Nathan
Although I could not explicitly identify the nonconvergent dependent variable, I was able to figure out iteratively which one was the offender. I suspect that the reason this was difficult is that most of my dependent variables are couples. This means, for instance, that if the offending dependent variable was concentration of a species, it may behave aberrantly near my final converged timestep, but so would the fluid velocity field, or pressure, or stress.
I ultimately guessed that the nonconverging dependent variable was the velocity field. In order to test that hypothesis, I went under the following interface:
Study 1 >> Solver Configurations >> Dependent Variables (I only have one solver step) >> Velocity Field
In this interface, I expanded the "Scaling" menu, and selected "Initial Value Based" from the drop down menu. My solution then converged, even for timesteps past where it had been failing before!
If velocity field had not been the nonconvergent dependent variable, I would have reset the scaling to the default (in my case, it was "From Parent"), and tried the same process on the next most likely candidate (in my case, concentration of gas).
I still don't know if there is a way to explicitly identify a nonconvergent dependent variable in a fully-coupled multiphysics problem. However, if someone knows how to do this, feel free to post here!
-Nathan