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 raza111 July 26, 2019 19:18

Convergence

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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?

 Светлана July 29, 2019 03:05

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

Svetlana

 BlnPhoenix July 29, 2019 11:58

Quote:
 Originally Posted by raza111 (Post 740155) 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.

 Светлана July 30, 2019 02:01

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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