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How can a time step be a negative value? confused by the model library example "fluid damper"

Posted Dec 15, 2011, 3:51 a.m. EST Version 4.2a 2 Replies

Pengfei Guo
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I happened to see that the time step is a negative value in the "fluid damper" which is a model in the model library.

How can a time step be a negative value? what does it mean?

I searched everywhere but find on such illustrations.

Thanks, guys. :)

have a good day!
2 Replies Last Post Dec 15, 2011, 7:46 p.m. EST
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Dec 15, 2011, 9:01 a.m. EST
Hi

I'm not sure I understand fully your question, but what I have notices is that when you perform a time solving sequence, and leave the solver free to select stepping, the algorithm might backtrack and perhaps give a negativ step, while trying to find the optimum way to progress ...

--
Good luck
Ivar
Hi I'm not sure I understand fully your question, but what I have notices is that when you perform a time solving sequence, and leave the solver free to select stepping, the algorithm might backtrack and perhaps give a negativ step, while trying to find the optimum way to progress ... -- Good luck Ivar
Pengfei Guo
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Posted: 1 decade ago Dec 15, 2011, 7:46 p.m. EST

Hi

I'm not sure I understand fully your question, but what I have notices is that when you perform a time solving sequence, and leave the solver free to select stepping, the algorithm might backtrack and perhaps give a negativ step, while trying to find the optimum way to progress ...

--
Good luck
Ivar


Thanks, Ivar.

I am wondering how other comsol uers can accept the negative time step.

The attached picture is the solver log of the model "fluid damper".

[QUOTE] Hi I'm not sure I understand fully your question, but what I have notices is that when you perform a time solving sequence, and leave the solver free to select stepping, the algorithm might backtrack and perhaps give a negativ step, while trying to find the optimum way to progress ... -- Good luck Ivar [/QUOTE] Thanks, Ivar. I am wondering how other comsol uers can accept the negative time step. The attached picture is the solver log of the model "fluid damper".

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