DDES Simulations, Courant Number and y+ Convergence

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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!

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