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Fail to find convergence when scaling down radiation problem
Posted 21 ott 2010, 04:27 GMT-4 1 Reply
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Hi !
I'm trying to compute how the temperature changes around a particle "hanging" in air using the HT with "Surface to surface" radiation and Transient solution.
The outer surface of the biggest circle is given a BC og 20 degC and the particles initial temperature is 5000 degC
The model works nicely when using a circle 2 cm of silica glass in diameter (best fit material in database), surrounded by a 20 cm circle of air.
When scaling the model down it crashes imidiately giving the following message for the time dependent solver:
Failed to find consistent initial values.
Last time step is not converged.
Changing the particle temperature to 1000 degC gives a solution, so I'm thinking this has to do with some scaling issue.
Have been reading a lot of posts here on the forum and tried suggestions given there, but still I get a failure.
I'm new to COMSOL so I was hoping some of you experienced users could provide me with some tips and tricks to get a solution.
Sorry for the long post - thanks alot for your help
Nils Eivind
I'm trying to compute how the temperature changes around a particle "hanging" in air using the HT with "Surface to surface" radiation and Transient solution.
The outer surface of the biggest circle is given a BC og 20 degC and the particles initial temperature is 5000 degC
The model works nicely when using a circle 2 cm of silica glass in diameter (best fit material in database), surrounded by a 20 cm circle of air.
When scaling the model down it crashes imidiately giving the following message for the time dependent solver:
Failed to find consistent initial values.
Last time step is not converged.
Changing the particle temperature to 1000 degC gives a solution, so I'm thinking this has to do with some scaling issue.
Have been reading a lot of posts here on the forum and tried suggestions given there, but still I get a failure.
I'm new to COMSOL so I was hoping some of you experienced users could provide me with some tips and tricks to get a solution.
Sorry for the long post - thanks alot for your help
Nils Eivind
1 Reply Last Post 21 ott 2010, 05:42 GMT-4
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Posted:
1 decade ago
Hi
If you have a non linear problem (and radiation exchange is rather of that kind) it's often usefull to get to your point by a parametric sweep to ramp gently your temperature or whatever variable to the final value
--
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If you have a non linear problem (and radiation exchange is rather of that kind) it's often usefull to get to your point by a parametric sweep to ramp gently your temperature or whatever variable to the final value
--
Lykke til
Ivar