Unexpected temperature rise in trasient heat transfer

[hs.simanto]

the details of the problem occurred is discussed thoroughly in the following link:

https://www.dropbox.com/s/e281dvezluygpci/transient%20problem.pdf

please help me out to find the exact reason of the problem occurred.

Thank you !

[Jon.Wilde]

Link disabled, can you post the pdf here?

[hs.simanto]

try this link please,im facing some problems directly uploading the pdf file to this forum.


https://www.dropbox.com/s/mr4lwwd6c4srg8c/transient%20problem.pdf

[Jon.Wilde]

Thanks I have it

Some pointers:

1. The domain should be longer. At least 5x the width in length on the outlet side, 3x on the inlet.
2. Apply Initial Conditions to volumes and not surfaces, I cannot tell which you have done here. Also apply to the air
3. You have flow turned off. Turn on Flow and Heat Transfer
4. Start with a small timestep size, perhaps 1s or 0.5s to allow the flow field to establish. You could even run this steady state with flow only and then re-initialise the Initial Condtions and run transient with heat transfer only (flow off), locking the converged flow results as they are

Thanks,

Jon

[hs.simanto]

thanks for your reply.  so you are telling me that i can solve this without assigning any temperature boudary condition & initial condition for flow only in steady state and then i can assign boundary temp condition and initial conditions to run heat transfer (flow off) in transient mood. Am i getting it right??

[Jon.Wilde · Accepted solution]

Yes, although I'd set all the BC's up in the first place, thermal too. They will just be ignored until you turn on thermal.

Then just re-initialise the Initial Conditions and run the transient, easy.