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Extension parametric - step size computation
Posted Jul 10, 2012, 5:31 a.m. EDT Heat Transfer & Phase Change, Computational Fluid Dynamics (CFD), Studies & Solvers 2 Replies
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I am doing using the non-isothermal flow physics to calculate convective heat transfer in a power electronics package.
In the log, I can read after almost each parametric step:
"Breakdown in parameter step size computation. Parameter step size unmodified."
Besides, the computation stops before it reaches the last parameter step (about halfway). I am using a extension-continuation parametric study in order to increase progressively the heat dissipated.
What does this error mean? How can I solve this problem and get the computation to work for all steps?
Thank you for your help.
In the log, I can read after almost each parametric step:
"Breakdown in parameter step size computation. Parameter step size unmodified."
Besides, the computation stops before it reaches the last parameter step (about halfway). I am using a extension-continuation parametric study in order to increase progressively the heat dissipated.
What does this error mean? How can I solve this problem and get the computation to work for all steps?
Thank you for your help.
2 Replies Last Post Jul 19, 2012, 1:32 a.m. EDT
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Posted:
1 decade ago
Hi Antoine.
I'm also doing a nonisothermal model and having the same error. I believe what it means is that the amount the parametric solver changes per calculation is held constant. So, for instance, if I am screening from an inlet pressure parameter of:
P = [10,100,1000,10000] Pa
Comsol initially calculates solutions by stepping the inlet pressure by an intermediate value of the first two steps, lets say 50 Pa. With this error, Comsol continues to step by 50 Pa, instead of increasing its step size, which may be more efficient for latter calculations such as going from 1 kPa to 10 kPa. So, it may just take the simulation longer but it will eventually reach the answer.
Does that make sense? I'm going to look at some parametric solver parameters and see what I come up with.
Ramsey
I'm also doing a nonisothermal model and having the same error. I believe what it means is that the amount the parametric solver changes per calculation is held constant. So, for instance, if I am screening from an inlet pressure parameter of:
P = [10,100,1000,10000] Pa
Comsol initially calculates solutions by stepping the inlet pressure by an intermediate value of the first two steps, lets say 50 Pa. With this error, Comsol continues to step by 50 Pa, instead of increasing its step size, which may be more efficient for latter calculations such as going from 1 kPa to 10 kPa. So, it may just take the simulation longer but it will eventually reach the answer.
Does that make sense? I'm going to look at some parametric solver parameters and see what I come up with.
Ramsey
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Posted:
1 decade ago
Hi
The solver tries to use intermediate stepping dependent on the results and the Jacobian it derives from the model, if you give large steps for a non linear problem, COMSOL might decide to do many intermediate steps. This behaviour can be adapted and changed in the solver sub node settings. But it is not always obvious what to change ;)
--
Good luck
Ivar
The solver tries to use intermediate stepping dependent on the results and the Jacobian it derives from the model, if you give large steps for a non linear problem, COMSOL might decide to do many intermediate steps. This behaviour can be adapted and changed in the solver sub node settings. But it is not always obvious what to change ;)
--
Good luck
Ivar