DDES Simulations, Courant Number and y+ Convergence

Product Support
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Hello,

Currently doing an internship on the design of paracyclonic structures, I am using R-WIND 3 to perform advanced aerodynamic analyses. I would need clarifications on the following points:

  1. Averaging of DDES results: In the context of an unsteady flow simulation (DDES), is it possible to perform time averaging of the results (pressure, velocity) directly within the software for data exploitation? If yes, what is the procedure to export or visualize these averaged results?
  2. Display of the Courant number (CFL): To ensure the stability of my unsteady calculations, I would like to monitor the Courant number. Is there an option or a result layer that allows displaying the distribution of the CFL number over the domain?
  3. Issue of y+ and mesh refinement: I am having difficulties reducing the value of y+. Despite local mesh refinement at the structure interface, the value remains too high to properly capture the boundary layer.
  • Does the software limit the thickness of the first boundary layer cell?
  • Do you have any recommendations on the parameters in the "Boundary Layers" tab to enforce a finer wall resolution?
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Hello tortuerenard89,
Thank you very much for your questions,

  1. Yes, it is possible to access average values in RWIND when using DDES. I recommend first defining evaluation zones. Then, you can extract the values either via the "Edit Zone Data" option or by using line charts, as illustrated in the figures below:

    image

    image

  2. To monitor the number of Currents, you can check the log file, especially in the RWIND solver transient output section, as shown in the corresponding image:

image

  1. Regarding boundary layer modeling, RWIND currently uses a standard wall function with high y+ values. Unfortunately, it is almost impossible to reach an acceptable y+ range in this setup. I have described the current approach as well as its advantages and limitations in the following knowledge base article, which I recommend you consult:

:backhand_index_pointing_right: https://www.dlubal.com/en/support-and-learning/support/knowledge-base/002040

Please feel free to contact me if you have any further questions,

Best regards,
Mahyar

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Thank you very much for your feedback!

1 Like
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Hello mahyar.kazemian,

I have a follow-up question regarding access to the Log.file data. It seems that my interface is different from yours: I cannot find this tab when running a DDES (transient) simulation, even though it appears correctly for steady-state studies.

Furthermore, the "Log file" is also inaccessible within the simulation window during the computation.

Could you please help me fix this? For context, I am using RWIND 3 Pro with a student license; does this license type affect the visibility of these features in transient mode?

Thank you in advance for your assistance.

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Hello @tortuerenard89,
Thanks for your feedback,

There is also an alternative way to access the log file data. If you can access the temporary file directory, for example, on my system, it is located at (it depends also on your project name):

C:\Users\Public\Documents\Dlubal\RWIND 3.08\Temp~RWIND_Simulation\TBC norm\RF_Simul\Sim001_V01\ofcase0),

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image1747Ă—776 49.4 KB

Then you will find a file named RWindSolverTransient. This file contains the relevant information:

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image1915Ă—969 125 KB

Please give it a try and let me know if you encounter any issues.

Kind regards,
Mahyar