topic Re: Problem with convergence plot / Automatic Convergence Assessment wrong? in CFD Forum

Problem with convergence plot / Automatic Convergence Assessment wrong?

fabian.franceschini — Wed, 13 Feb 2019 10:12:45 GMT

Hello guys.

So here is my conflict.

After 353 iterations Autodesk CFD 2019 automatically stopped calculating, since the option Automatic Convergence Assessment was on.

I ran some more iterations, to ensure that the result is really convergenced out.

Shockingly, the result after the 353 iterations is not convergenced.

What is wrong here?

Should I make even more Iterations or just take the result at 353 iterations?

I am highly confused and if someone could help me out that would be great!

Any help is appreciated.

Thanks

Fabian

Re: Problem with convergence plot / Automatic Convergence Assessment wrong?

tomasz.kasperek — Wed, 13 Feb 2019 14:36:18 GMT

Hi, @fabian.franceschini

Thank you for contact with Autodesk Support

Please try to change the settings of automatic convergence as follows:

An important is to both of operation - move the slider to right and checkmark the Edit individually position.

It allows ordering by the user to stop the analysis after reach stability of convergence.

Best Regards,

Re: Problem with convergence plot / Automatic Convergence Assessment wrong?

fabian.franceschini — Wed, 13 Feb 2019 21:00:08 GMT

The solution was running 1001 iterations. Anyways I am shocked that the Automatic Convergence Assessment stopped the calculation after just 353 iterations...

Convergence plot is now fine:

Re: Problem with convergence plot / Automatic Convergence Assessment wrong?

Anonymous — Thu, 14 Feb 2019 05:43:16 GMT

Hi @fabian.franceschini

In my humble opinion, there is no reason for you to be shocked. The Automatic Convergence Tool algorithm is not doing anything wrong here. For a closer look, you can focus on the variation of relevant DOF only and\or global/local monitor points. Cross-checked with Resid In and Resid Out, and you will find out that the actual level of 'convergence' reached. As a reminder, you are the one who is responsible for residuals' order of magnitude. The algorithm is triggered whenever flat lines of your choice are detected. Waiting for more digits/accuracy/additional iterations to complete is up to you according to the validation of the model you need.