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Posted: 1 decade ago 27 mar 2012, 09:30 GMT-4

The analysis is converging according to your log file. “Out” means results are saved at this point. COMSOL saves results at the times that correspond to your specified range(0,0.5e-7,24e-6). To see convergence plots you should check the “Generate convergence plots” box in the settings window of the Study node. Nagi Elabbasi Veryst Engineering

Posted: 1 decade ago 28 mar 2012, 02:35 GMT-4

[QUOTE] The analysis is converging according to your log file. “Out” means results are saved at this point. COMSOL saves results at the times that correspond to your specified range(0,0.5e-7,24e-6). To see convergence plots you should check the “Generate convergence plots” box in the settings window of the Study node. Nagi Elabbasi Veryst Engineering [/QUOTE] Dear Nagi Thanks a lot for replying! Firstly how do we know looking at the log file that the analysis is converging? Secondly if you have noticed at some time instances like 1e-7,1.5e-7,2e-7,2.5e-7,3.0e-7,3.5e-7,4e-7,4.5e-7,5e-7 the line is a blank followed by -out. But instances such as 5e-8,5.5e-7,6e-7,6.5e-7,7e-7 has out different from that mentioned earlier. Ive highlighted the points in the log file that i have attached in this post. Is there something that im not reading properly. Thanks a lot again! Regards Glenston

Attachments:

• log_file.doc

Posted: 1 decade ago 28 mar 2012, 08:06 GMT-4

You're welcome! The analysis goes all the way so it must be converging based on the convergence tolerances selected for both spatial convergence and time integration convergence. If it did not converge at a certain time COMSOL would stop, and also give an error message. In your case, it also seems that COMSOL is not checking time integration errors because you specify manual time stepping. I’m not sure why the –out lines look different sometimes. My understanding is that if –out is on the same line as other text it means that COMSOL outputted that solver step directly. If it is on a line of its own then COMSOL did some interpolation between solutions. That doesn’t fit your case since you manually specified a constant step size. Maybe some numerical round-off errors. Nagi Elabbasi Veryst Engineering

Posted: 1 decade ago 29 mar 2012, 01:55 GMT-4

Hi I can confirm that my understanding is that several out grouped comes from COMSOL interpolating the results you demanded, while as in your log file COMSOL is running in "automatic mode and gets to a point just above/below your values and interpolates to get at precisely your value, so as Nagi says its an interpolation issue. But on the other side, depending on what you are simulating, you might not need all these intermediate steps, try a "strict" stepping, you might gain time, but check carefully the results by comparison as if your steps are coarse w.r.t. the gradients involved, the results might be less precise -- Good luck Ivar

Posted: 1 decade ago 29 mar 2012, 02:50 GMT-4

Hi Ivar, Thanks a lot for replying. Checking the case when i use strict and intermediate time stepping. A comparison should give me a good understanding on how the time stepping works. Regards Glenston