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Solvers that good at suddenly strong transient ?
Posted May 2, 2011, 10:12 a.m. EDT Studies & Solvers Version 4.1 1 Reply
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If a model contains suddenly strong transient, which solvers should I choose ?
1 Reply Last Post May 2, 2011, 3:58 p.m. EDT
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Posted:
1 decade ago
Hi
I believe the issues is a bit more multi-disciplinarythan that ;)
My advise would be to try first the default COMSOL choice, but help the solver by giving ranges of steps at a thight space around regions you now are "spiky". Then to ensure that your transition are made "smooth" with Heavyside type functions (many built-in into V4 default functions)
Finally the "stepping" settings of COMSOl are default "automatic" which mostly adapt best to assymptotical regular responses. If you have periodic driving signals, its worth to use "strict" or "intermediate" to tell the solver to either strictly solve your values (only) or to adjust with AT LEAST ONE step inbetween your defined steps. In automatic mode, after a "calm" region with a low gradient change, the sovler could decide of a large step that overshoots a smal spiky behaviour you have define. Then the interpolated results will appear "flat" and you will miss your features.
Anyhow, too spiky driver functions make the life for the solver very tough and it might not converge at all within it's predefined number of iterations
--
Good luck
Ivar
I believe the issues is a bit more multi-disciplinarythan that ;)
My advise would be to try first the default COMSOL choice, but help the solver by giving ranges of steps at a thight space around regions you now are "spiky". Then to ensure that your transition are made "smooth" with Heavyside type functions (many built-in into V4 default functions)
Finally the "stepping" settings of COMSOl are default "automatic" which mostly adapt best to assymptotical regular responses. If you have periodic driving signals, its worth to use "strict" or "intermediate" to tell the solver to either strictly solve your values (only) or to adjust with AT LEAST ONE step inbetween your defined steps. In automatic mode, after a "calm" region with a low gradient change, the sovler could decide of a large step that overshoots a smal spiky behaviour you have define. Then the interpolated results will appear "flat" and you will miss your features.
Anyhow, too spiky driver functions make the life for the solver very tough and it might not converge at all within it's predefined number of iterations
--
Good luck
Ivar