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Free Convection: Stationary or Time-Dependent Study

Posted 04.06.2015, 19:14 GMT-4 Fluid & Heat, Heat Transfer & Phase Change, Computational Fluid Dynamics (CFD) Version 5.0 2 Replies

Akim Borbuev
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Dear all,

So far in all my free convection simulations I have used Time-Dependent Study but it takes a lot of time, weeks and even months to get the results. The point is I am not interested in transient study, I am looking for steady-state solution. I have seen some models from Application Gallery (Natural Convection Cooling of a Vacuum Flask, Free Convection in a Water Glass, etc.) and I have replicated them using my case, however, it is not converging. But if run the same model with time-dependent study Comsol is solving it but too slowly as I mentioned before. Any idea and/or help will be appreciated.

Regards,
Akim
2 Replies Last Post 28.03.2017, 10:49 GMT-4
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Hello Akim Borbuev

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Meryeme BOUMAHDI
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Posted: 8 years ago 28.03.2017, 09:06 GMT-4
Hi
I have the same problem did you find a solution or not
Hi I have the same problem did you find a solution or not
Walter Frei COMSOL Employee

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Posted: 8 years ago 28.03.2017, 10:49 GMT-4
Hello,
You may want to try this technique:
www.comsol.com/blogs/viscosity-ramping-improves-the-convergence-of-cfd-models/
It may also be that your system has no true steady-state solution, but only an oscillatory time-varying solution. In that case, you will need to run the transient model, but in that case, use probes:
www.comsol.com/blogs/probing-your-simulation-results/
to monitor your solution at a few key points of interest. If the solution is oscillating about a value, then it is reasonable to stop the solution without running to completion.
Hello, You may want to try this technique: https://www.comsol.com/blogs/viscosity-ramping-improves-the-convergence-of-cfd-models/ It may also be that your system has no true steady-state solution, but only an oscillatory time-varying solution. In that case, you will need to run the transient model, but in that case, use probes: https://www.comsol.com/blogs/probing-your-simulation-results/ to monitor your solution at a few key points of interest. If the solution is oscillating about a value, then it is reasonable to stop the solution without running to completion.

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