Convergence Issues in CFD

Project Support
1

Hi there,

I am doing a Non-Compressible CFD on one of my FSAE projects with rear wing. I am facing problems with unstable Omega and K values. Apart from that, I am also facing problems in convergence of pressure.

Link to my project: https://www.simscale.com/workbench/?pid=2225782415852698681&mi=spec%3A24d46af7-6a09-4f8b-83c5-db5b73db392d%2Cservice%3ASIMULATION%2Cstrategy%3A89

image
image1575×763 44.3 KB

As you can see the residuals plot, I haven’t received a proper convergence in pressure and have unstable omega and K values.

Attaching other plots of convergence also for better understanding,

  1. walls

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    image1577×809 44.6 KB

  2. Outlet

    image
    image1581×817 58.3 KB

  3. Inlet

    image
    image1583×806 80.6 KB

  4. Domain

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    image1578×803 49.2 KB

I am guessing the problem is at inlet as the values over there are not completely stable. I am further trying with enlarged cartesian box I used for refinement around car because the front face was really close to the nosecone which might have created this error but I am not sure.

Hope you guys can help…

Cheers!!

2

Hi there, thank you for using the forum! When it comes to convergence, just checking the Residuals tab should be enough. Have a look here: How to Check Convergence of a CFD Simulation? | SimScale

Yours seem just fine, these oscillations will be omitted if you decrease the absolute tolerance here:

omega
omega303×1012 42.4 KB

Best regards,
Fillia

3

Hello @tsite ,

I tried with your suggested settings and I got a fair convergence. Just a question, what happens on reducing the absolute tolerance of the said factors? Do they seize to take into account that specified change or something else?

Also, I am again having same issues but with standard mesh this time.

Please check ‘16 4 21 e423 e423 s1223 v2’ with sim run named ‘50 kmph new’

image
image1575×815 95 KB

As you can see, the residuals plot is of course not converging. So what would you suggest here? I am already at 8M big mesh so I don’t think finesse should be added to it and the quality of the mesh is pretty good also.

Hope you can help…

Cheers!!