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Would you consider this as a converged solution? |
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December 14, 2021, 03:06 |
Would you consider this as a converged solution?
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#1 |
New Member
F
Join Date: Oct 2021
Posts: 10
Rep Power: 4 |
Good day,
Would you consider the attached plots as those of a converged solution? My concerns are: - Is it normal that I need like 200 iterations for p, while only a few for the other variables? - Is it normal that the p residual is kind of fluctuating? - Is it normal that the p residual is like 2 order of magnitude higher than the other residuals? Note: - the discontinuities at about 1.4s is due to the fact that I changed the time step on the go. - I have got a time variant BC, with the input velocity that raises from 0 to its final value at 2s. Thanks |
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December 14, 2021, 07:36 |
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#2 |
New Member
Federico Nahuel Ramírez
Join Date: Dec 2020
Location: Spain
Posts: 16
Rep Power: 5 |
Hello fran.cesc,
In my opinion the residuals look good. Regarding your doubts, it is normal that the residuals fluctuate as long as the amplitude is small, just as the number of iterations for each variable changes between cases and solvers. At least that has been my experience, someone correct me if I am wrong. As for the convergence, I think it is better to check it by analyzing how much some variable of interest of your problem varies, such as CL and CD if it is an airfoil, Instead of looking only at residuals. |
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December 15, 2021, 04:27 |
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#3 |
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Daniel
Join Date: Jan 2021
Posts: 39
Rep Power: 5 |
Hey there,
let me give my 2 cents about your case. - without a log file, case description, solver/schemes settings its hard to evaluate your case - p-Iterations of 200 is really high - shouldn´t be so, mostly due to fvSolution settings (tolerance 0.0 maybe?) - p residual fluctuating can be okay, but not in this range of 0.01, this is to huge to let it be okay with it. What solver are you using? - so pressure boundary conditions maybe also a problem here - transient cases are robust and stable, you should go to 1e-3 with residuals at least (its possible, look at your other residuals) - timeStepErrors are fine - monitor your variables of interest (massflow, forces, liftcoefficent...) and evaluate convergence on these, do not focus only on residuals |
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December 15, 2021, 06:35 |
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#4 | |||||
New Member
F
Join Date: Oct 2021
Posts: 10
Rep Power: 4 |
Thanks for your reply
Quote:
Quote:
Quote:
For the pressure BC, I am using zeroGradient at the inlet and fixedValue (0) at the outlet. At the top and bottom, I am using a symmetry condition; whereas I use zeroGradient on the walls. Quote:
Quote:
I have attached the main files of my case. Any suggestion about what the problem you were mentioning could be please? Thanks Kind Regards |
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