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Malfunctioning of HT Module

Posted Oct 1, 2012, 2:42 a.m. EDT 3 Replies

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I am not certain why this result is appearing before me. This is a simple HT case where we had provided the temperature at two boundary as 597 K and 297 K just to see the intermediate temperature profile and propagation of heat within time domain.

Here the result is quite surprising like, the temperature gone down below the lower temp ( 297 K) at the near boundary of the higher temperature.

Can Anyone explain this, why this is happening.

Rgrds,

Ishant jain

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3 Replies Last Post Oct 2, 2012, 1:06 a.m. EDT
Jesus Lucio
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Posted: 1 decade ago Oct 1, 2012, 10:14 a.m. EDT
Hello,

Perhaps the problem is the discontinuity in initial conditions in T in one of the boundaries. Any (in space or time) discontinuity yields convergence problems easily. You could try a ramp function for the boundary conditon, like:
293.15[K]+300[K]*rm1(t/1[s]), where rm(t) has been defined as a ramp function, rising smoothly from 0 to 2 seconds, for instance.

A finer mesh in the 'problematic' boundary is also advised.

Bye,

Jesus.
Hello, Perhaps the problem is the discontinuity in initial conditions in T in one of the boundaries. Any (in space or time) discontinuity yields convergence problems easily. You could try a ramp function for the boundary conditon, like: 293.15[K]+300[K]*rm1(t/1[s]), where rm(t) has been defined as a ramp function, rising smoothly from 0 to 2 seconds, for instance. A finer mesh in the 'problematic' boundary is also advised. Bye, Jesus.
Tolga Y. Ozudogru
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Posted: 1 decade ago Oct 2, 2012, 12:18 a.m. EDT
Hi Ishant,

The problem is related to time steps and mesh size.

Please check this thread: www.comsol.com/community/forums/general/thread/16808#p46163

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Tolga
Hi Ishant, The problem is related to time steps and mesh size. Please check this thread: http://www.comsol.com/community/forums/general/thread/16808#p46163 -- Tolga
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Posted: 1 decade ago Oct 2, 2012, 1:06 a.m. EDT
The finer meshing at the bounder layer works well.

I will request you to please give some detail about this ramp function.


Hello,

Perhaps the problem is the discontinuity in initial conditions in T in one of the boundaries. Any (in space or time) discontinuity yields convergence problems easily. You could try a ramp function for the boundary conditon, like:
293.15[K]+300[K]*rm1(t/1[s]), where rm(t) has been defined as a ramp function, rising smoothly from 0 to 2 seconds, for instance.

A finer mesh in the 'problematic' boundary is also advised.

Bye,

Jesus.





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ishant.jain@tatasteel.com
The finer meshing at the bounder layer works well. I will request you to please give some detail about this ramp function. [QUOTE] Hello, Perhaps the problem is the discontinuity in initial conditions in T in one of the boundaries. Any (in space or time) discontinuity yields convergence problems easily. You could try a ramp function for the boundary conditon, like: 293.15[K]+300[K]*rm1(t/1[s]), where rm(t) has been defined as a ramp function, rising smoothly from 0 to 2 seconds, for instance. A finer mesh in the 'problematic' boundary is also advised. Bye, Jesus. [/QUOTE] -- ishant.jain@tatasteel.com

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