Menu

Discussion Forum

New Discussion
Filtern

Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

How to define a maximum value for a dependent variable?

Posted 11.04.2011, 11:55 GMT-4 Battery Design, Parameters, Variables, & Functions Version 4.1 2 Replies

Ertan Agar
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

I have been trying to develop a performance model for an electrochemical system.
However, I got some evaluation errors of powers or logarithms when starting
the solver. This is due to concentrations getting negative values at some
solver step. I need to assure that I do not evaluate negative values, and use a maximum concentration value for all species like max(1e-9, c).

How can I define it?

Thanks,

Ertan
2 Replies Last Post 17.06.2015, 01:42 GMT-4
Ertan Agar
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 12.04.2011, 20:13 GMT-4
I have just found how to define it. If you use max(c, 1e-9) everywhere in the model instead of "c", the max function will return 1e-9 if the concetration is lower than 1e-9. Therefore, you can eliminate errors due to getting negative concentrations values at some solver step.

I have just found how to define it. If you use max(c, 1e-9) everywhere in the model instead of "c", the max function will return 1e-9 if the concetration is lower than 1e-9. Therefore, you can eliminate errors due to getting negative concentrations values at some solver step.
Adnan Brkic
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 9 years ago 17.06.2015, 01:42 GMT-4
Hi,

where have I to type in the function?

Best regards,
Adnan
Hi, where have I to type in the function? Best regards, Adnan

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.

Suggested Content