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Old   July 26, 2019, 19:18
Post Convergence
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Abbas Raza
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Hello all, I'm fairly new to CFD and still trying to get a hang of it. I have performed this simulation and convergence criteria were all set to default. Does this iteration graph show that my solution is converged?
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Old   July 29, 2019, 03:05
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Svetlana Tkachenko
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Hi raza111


1. Is this the first time you are running a CFD simultion?


2. Your continuity has converged to the value of 1e-1. You do not need to run the simulation any further, this is unlikely to improve convergence.


3.The 1e-1 level may be insufficient. It is often needed to converge to 1e-4 or lower. Please do mesh independence study.


4. I think this FAQ is relevant:


https://www.cfd-online.com/Wiki/Ansy...gence_criteria


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Old   July 29, 2019, 11:58
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Quote:
Originally Posted by raza111 View Post
Hello all, I'm fairly new to CFD and still trying to get a hang of it. I have performed this simulation and convergence criteria were all set to default. Does this iteration graph show that my solution is converged?
1) Your simulation has not yet reached your convergence criteria (something or order 1e-3 i assume), so no, the simulation is not converged yet.

2) 80 Iterations is not really a lot. I rarely see simulations meeting the convergence criteria with this little amount of iterations, even with good initial values.

3) The graphs still indicate global convergence behaviour, so my advice would be to let it run further.

4) There is really no need to abort the simulation at this point since you are likely to improve result accuray with further iterations.

5) Always check for a flow quantity of interest, not just the residuals, to judge the level of convergence.
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Old   July 30, 2019, 02:01
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Svetlana Tkachenko
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Interesting note that it may converge in the future which I thought it wouldn't (your point number two). Thank you for this correction. I hope the author can check and confirm this.
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