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inner convection problem
Posted Oct 19, 2010, 4:11 p.m. EDT 8 Replies
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I have the problem with internal convection heating problem. I try to model as simple thing as water filled rectangle (in 2D) with temperatures defined in lower left and higher right corners as hot and cold respectively. I use conjugate heat transfer module, and i change the default model to fluid - it changes the module to Non-isothermal flow (nitf).
Then I add two temperatures at two corners of box and try to solve it.
Unfortunately it never solved and error message is not helping too much:
Failed to find a solution:
Maximum number of Newton iterations reached.
Returned solution has not converged.
I have tried different mesh resolutions but without success.
Could you help me to find the place where I do mistake?
Best regards,
Michal Radziwon
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Maximum number of Newton iterations reached:
The nonlinear solver could not reduce the error below the desired tolerance in the specified maximum number of iterations. This is sometimes a sign that the Jacobian is not complete or badly scaled. It may even be almost singular, if the system is underdetermined. If the returned solution seems reasonable, it might be enough to restart the solver with this solution as the initial guess.
Returned solution has not converged:
The solution returned by the stationary solver is not to be trusted. It might, however, be useful as initial guess after modifying equations or solver settings.
I am not sure if these explanations help, but better than nothing.
Good luck,
Özen
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Despite i found the explanation of the errors I need to find the cause why it happens. Therefore i used simplest instance of my problem, unfortunately without effect :/
Maybe I could send you my file, to show what is going on there?
Best regards,
Micha? Radziwon
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So I can describe you step by step what have I done.
-- I want to obtain the velocity field which will appear in rectangular tunnel, when part of bottom will be heated, while part of top cooled. I expect to obtain a circulation of water inside.
1. Start 2D model with conjugate heat transfer (laminar) with stationary study
2. I draw 1x1m square with centre at 0.0
3. I put two points at 0.25,0.5 and -0.25,0.5 - those together wth closest corners will define hot and cold plates
4. i added finer mesh
5. In "conjugated Heat transfer" i changed Default model to fluid - the name changed to non-isothermal flow
6. I added two "Temperatures" one 293.15[K]+50 at the bottom left edge ([-0.5,-0.5;-0.25,-0.5]) and 293.15[K]+20 at top right edge ([0.5,0.5;0.25,0.5])
7. Solve.... and i cannot get any field from there ;/
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Do you expect such a result? (see the attachment)
Regards,
Özen
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