[JMDag2004]

Hello everyone, I am using the seulex ode solver for a hydrogen /air combustion scenario. I received a run time warning:

FOAM Warning :
From function seulex::solve(scalar& x, scalarField& y, stepState&
in file ODESolvers/seulex/seulex.C at line 255
step size underflow :2.64698e-23.

I've searched the internet and the blogs here on this site and I haven't found anything that addresses the cause of this warning. I feel like it is rooted in the concentration gradients or potentially the pressure or temperature which are used to calculate reaction equilibrium rates because it's crashed the simulation due to a floating point exception. Or I should say the warning is expressed rapidly just before the simulation fails. Can anyone help me understand what causes this error please? I would really appreciate the help! I can post any of my files if necessary.

[JMDag2004]

I guess no one knows?

[dimaCFD]

hi,

Did you try other ODE solvers? The usual, I use RADAU5 for this staff =)


Thx, Dmitry

[JMDag2004]

Thank you Dmitry for your response, I've been searching high and low for information on the ODE solvers within OpenFOAM and there just isn't much information available. It's a fairly stiff system and the only information I was able to find suggested using the Seulex solver for stiff systems.

[dimaCFD]

I could suggest to try my solver edcPisoFoam =) which is based on rhoReactingFoam and incorporates the Eddy Dissipation Concept with a detailed chemistry approach for the turbulence-chemistry interaction. I have finished my PhD related to OpenFOAM and turbulent combustion modeling with OpenFOAM this year using this solver, so it has good validation and references =)

edcPisoFoam utilizes the RADAU5 algorithm which is implicit 5th order RK method for stiff chemistry kinetics.

You can download it for free from: http://www.edcpisofoam.decgroup.org/

[JMDag2004]

Thank you very much for your suggestions as well as your offer to use the solver you developed. I just downloaded the solver and will probably spend the next week or so going though it. I like the challenge of creating my own but look forward to learning from the construction of yours. Very much appreciated!

Regards
Josh

[demolaoye]

Hello, JMDag2004.

Did you get a solution to your problem? If yes, I do have the same problem and would appreciate your help.

Thank you!

[comingdaytime]

Have you tried to decrease the relative tolerance. I decreased from 0.01 to 0.0001. That warning message doesn't appear then.

[zhangyan]

Hi Dmitry,
I cannot dowload the code of edcPisoFoam from www.edcpisofoam.decgroup.org.
can you send me a copy of it?
my email: zytju@tju.edu.cn
Thank you!

[charryzzz]

I have the same warning, but luckily my case does not crash, I just wonder what case this warning and does this warning affect the result?

[sanjeev_adhikari]

Originally Posted by dimaCFD

I could suggest to try my solver edcPisoFoam =) which is based on rhoReactingFoam and incorporates the Eddy Dissipation Concept with a detailed chemistry approach for the turbulence-chemistry interaction. I have finished my PhD related to OpenFOAM and turbulent combustion modeling with OpenFOAM this year using this solver, so it has good validation and references =)

edcPisoFoam utilizes the RADAU5 algorithm which is implicit 5th order RK method for stiff chemistry kinetics.

You can download it for free from: http://www.edcpisofoam.decgroup.org/

webpage is not available to download can you email it ? I am having similar issues with stiff ODE problem. i am looking for RADAU5 email: 071bme435sanjeev@ioe.edu.np

[sante_junior]

Hi Dmitry,
I can't download the edcPisoFoam code from www.edcpisofoam.decgroup.org . Can you send me a copy?
My email is: santelima8@gmail
Thanks!