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Error: The recorded Historical maximum value decreases during simulation?!

Posted Dec 31, 2019, 7:28 p.m. EST Structural & Acoustics, Studies & Solvers, Equation-Based Modeling Version 5.5 2 Replies

Yu Zhang
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Dear All:

I followed the approach given in the Blog article, https://www.comsol.com/blogs/using-the-previous-solution-operator-in-transient-modeling, to record the maximum historical value. The following expressions are used,

u-nojac(if(T>u,T,u)); MaxTemp = max(T,u) and a previous soluton node

However, I found the recorded maximum may decrease during the simulation. In my simulation, even a tiny decrease is not allowed. Did anyone also encounter such a issue? How to solve it?

Thanks a lot.

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Yu Zhang
2 Replies Last Post Jan 1, 2020, 5:20 p.m. EST
Henrik Sönnerlind COMSOL Employee

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Posted: 5 years ago Jan 1, 2020, 3:33 p.m. EST

Hi Yu,

My best guess is that it is a postprocessing artefact. The stored values in each point are probably OK, and what you see is an effect of interpolation or extrapolation.

Regards,
Henrik

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Henrik Sönnerlind
COMSOL
Hi Yu, My best guess is that it is a postprocessing artefact. The stored values in each point are probably OK, and what you see is an effect of interpolation or extrapolation. Regards, Henrik
Yu Zhang
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Posted: 5 years ago Jan 1, 2020, 5:20 p.m. EST
Updated: 5 years ago Jan 2, 2020, 3:04 p.m. EST

Hi, Henrik,

Thank you for your reply. In my model, the historical maximum value is not allowed to decrease. Could you please provide me a way to achieve that? Should I use the value at the Gauss point?

In addition, when I was trying to use the time derivative of the maximum value, say d(V_max,TIME), in my model, I always got a message:

Failed to find consistent initial values. Last time step is not converged.

Could you please give me some help about that?

Thank you for your help.

Happy new year

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Yu Zhang
Hi, Henrik, Thank you for your reply. In my model, the historical maximum value is not allowed to decrease. Could you please provide me a way to achieve that? Should I use the value at the Gauss point? In addition, when I was trying to use the time derivative of the maximum value, say d(V_max,TIME), in my model, I always got a message: Failed to find consistent initial values. Last time step is not converged. Could you please give me some help about that? Thank you for your help. Happy new year

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